Mainship 350 / 390 Trawler
Built ?–2005 by Mainship
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About the Mainship 350 / 390 Trawler
Researched from public sources for this model. Any individual boat may have been modified or repowered — confirm before relying on any figure.
- Built
- ?–2005
- Builder
- Mainship
- Length
- 39.75 ft
- Beam
- 14.17 ft
- Draft
- 3.67 ft
- Displacement
- 22,000 lb
- Hull
- fiberglass-cored
- Hull / keel
- semi-displacement
- Propulsion
- inboard
- Fuel
- 300 gal
- Water
- 130 gal
- Holding
- 30 gal
- Water heater
- AC
- Generator
- fitted on some boats
- Bow thruster
- standard
- Stern thruster
- often added later
Tank capacities — where the figures come from
-
Fuel 300 gal
“Fuel: 300 gallons in 2-150 gallon aluminum tanks” — search excerpt (2001), grayandgrayyachts.com · “300 gallons of fuel” — search excerpt (2001), boattrader.comTwo listings agree on two 150 gal aluminum tanks, 300 gal in total. No builder document was found.
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Water 130 gal
“Water: 120 gallons in 2 poly tanks” — search excerpt (2001), grayandgrayyachts.com · “130 gallons of water” — search excerpt (2001), boattrader.comListings split between 120 and 130 gal; our earlier figure of 130 is kept.
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Holding 30 gal
“Holding: 35 gallons in poly tank” — search excerpt (2001), grayandgrayyachts.com · “a 30-gallon holding tank” — search excerpt (2001), boattrader.comListings split between 30 and 35 gal; our earlier figure of 30 is kept.
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Water heater AC (Kuuma)
“New 6 gallon, 1500w, like-for-like replacement. Kuuma 1881 water heater – Mainship 390” — broker listing, shellerina.comOne owner's blog about a 390 shows a 6 gal heater replaced with the same size; the Kuuma is the replacement, so the original brand isn't known. No builder source was found.
Tanks are often replaced or added on older boats — check the tank labels or a survey for yours.
Thrusters and steering — where this comes from
-
Bow thruster standard
“To make docking easier, a Bow Thruster is standard” — broker listing, curtisstokes.net · “All single's came with thrusters” — search excerpt, trawlerforum.com · “We specifically looked for a single-screw model with bow-thruster, which is the more common configuration.” — broker listing, shellerina.comA broker listing and an owner on Trawler Forum both say single-engine boats came with a bow thruster, but no builder document or review confirms it was standard, and twin-engine boats may not have had one. Our earlier note of an early 4 hp unit later upgraded to 7 hp wasn't found in any source; one listing names a Sleipner (Side-Power) thruster.
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Stern thruster often added later
“Knot Envy has an additional Stern Thruster ... Stern Thruster addition, controls, remote, batteries, 24v Charger” — broker listing, curtisstokes.net · “2001 MAINSHIP 390 TRAWLER ... BOW & STERN THRUSTERS” — search excerpt (2001), yachtworld.comTwo separate boats have stern thrusters, one clearly added by an owner, and no builder source lists one. Murray Yacht Sales also says single-engine boats are often paired with a bow and even a stern thruster.
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Steering unknown
“Mainship did opt for good to best accessories. SeaStar steering, Vacu-Flush head, Rule pumps” — search excerpt, trawlerforum.com · “Does anyone know where the hydraulic steering reservoir ( if there is one) on a Mainship 390?” — search excerpt, trawlerforum.comTwo owner posts on Trawler Forum describe factory SeaStar hydraulic steering; no builder or magazine source was found.
Thrusters and steering are often replaced — check the units on your boat before ordering parts.
Sources disagree on first year — left blank rather than guessed.
Called the 390 from 1999. LOA 39.75 ft includes platform and pulpit; hull length 34.75 ft. Engines ran up to 480 hp: single or twin Yanmar or Volvo, single Cat or Cummins. Blistering reported on under 1% of hulls per factory records. Tends to wander in following seas.
Engines fitted
-
Caterpillar 3116 — 300 hp, diesel, single
standard
The usual engine in early (350-era) boats per a broker history; a survey review and forum owners also report the single 3116 and its reliability complaints.Sources: murrayyachtsales.com · yachtsurvey.com · trawlerforum.com
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Caterpillar 3126 — diesel, single
factory option
Forum owners report single 3126s in 2002-2003 390s; hp not stated in the sources read.Sources: trawlerforum.com
-
Cummins 6BTA 5.9 — 330 hp, diesel, single
factory option
Factory offered a single Cummins; an owner cites a 2000 390 with a 330 hp 6BTA. The survey review calls the 6BTA the better choice.Sources: denisonyachtsales.com · trawlerforum.com · yachtsurvey.com
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Yanmar 6LY — 370 hp, diesel, single
factory option
HMY: single 370 hp Yanmar cruises 10-12 kn; forum cites a 2003 390 with a 6LYA.Sources: hmy.com · trawlerforum.com
-
Yanmar — 230 hp, diesel, twin
factory option
HMY: twin 230 hp Yanmars cruise about 14 kn; Denison confirms twin Yanmars were a factory choice.Sources: hmy.com · denisonyachtsales.com
-
Volvo Penta — diesel, single or twin
factory option
Denison lists single and twin Volvos among factory options; no model or hp given.Sources: denisonyachtsales.com
Boats of the same model can differ — check which engines yours actually has before ordering parts.
Generator
“The Mainship 390 was typically shipped with an adequately sized diesel generator” — broker listing, shellerina.com · “Kohler 8 kw Generator” — search excerpt (2000), taityachts.net · “Kohler 8 kW generator” — search excerpt (2003), powerboatlistings.com · “8kw Kolher Generator” — search excerpt (2004), americanyachts.com
Nearly every 390 seems to have a generator, but no source confirms whether it was standard or optional. They aren't marked as often added later, because they appear to have been fitted at delivery. No generator was found for a boat from the 350 years (1996-98).
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Kohler — 8 kW, diesel
Seen on three separate 390s for sale (2000, 2003, 2004); an owner says 390s were typically delivered with a diesel generator, but no builder list says standard or optional.“Kohler 8 kw Generator” — search excerpt (2000), taityachts.net · “Kohler 8 kW generator” — search excerpt (2003), powerboatlistings.com · “8kw Kolher Generator” — search excerpt (2004), americanyachts.com
Generators are often replaced or added — check the unit's own plate before ordering parts.
Known problems for this model
-
Leaking swim-platform bustle hull
The molded transom extension (bustle) under the swim platform is known to leak and fill with water, soaking its foam; a factory fix arrived around 2002 and many older boats have had a hatch, drainage or pump added.trawlerforum.com
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Wet balsa core in decks deck
Decks and hull sides above the waterline are balsa-cored; poorly sealed fasteners, stanchions and the windlass rode hole let water in, causing soft spots on the flybridge deck and near the steps.trawlerforum.com
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Cat 3206 soft-block failures engine
Some boats with the Caterpillar 3206 option suffered early block failures (reported around 500 hours); most have since been repowered, but check engine history.trawlerforum.com
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Undersized early bow thruster other
Early boats had a 4 hp bow thruster that is weak in wind; Mainship later went to a 7 hp unit. Slow-speed handling in wind is not the boat's strength.denisonyachtsales.com · trawlerforum.com
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Hard-to-replace sanitation hoses plumbing
Original sanitation hoses were installed in a way that makes replacement a large job.trawlerforum.com
Engines & parts
Caterpillar 3116 parts: limited
Factory standard engine — you entered “Caterpillar 3116”
Supported by Cat dealers by serial number; aftermarket rebuilders (e.g., Big Bear Engine) sell parts and address known problems. Some 3116s built in France ('soft block') were problematic and owners are told to check serial numbers with Cat.
Parts sources: Big Bear Engine Company, Diesel Pro Power
Common problems (4)
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Failures in high-load use engine
3116s generally do fine in trawlers but problems show up in fast boats run near full power for long periods; poor propping that overloads the engine ages it quickly.trawlerforum.com
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'Soft block' engines engine
A batch of French-built blocks had a reputation for early failure, sometimes within a few hundred hours.trawlerforum.com
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Injectors, fuel rack and heads fuel
Owners and rebuilders report injector/injector-cup, fuel rack and cylinder head problems; good maintenance history matters when buying.4btengines.com · facebook.com
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Low turbo/exhaust mixer height exhaust
The low-mounted turbo and exhaust mixer make it harder to get adequate exhaust riser height, so the exhaust installation needs care to avoid water backflow.trawlerforum.com
Maker’s service schedule (18)
| Engine oil & filter change | 250 hrs or 1 yr | “Every 7500 L (2000 US gal) of Fuel or 250 Service Hours or 1 Year ... Engine Oil and Filter - Change” — manufacturer, oxfordyachtagency.com |
| Fuel filters & water separator | 250 hrs or 1 yr | “Every 7500 L (2000 US gal) of Fuel or 250 Service Hours or 1 Year ... Fuel System Primary Filter/Water Separator Element” — manufacturer, oxfordyachtagency.com |
| Raw-water pump impeller | 250 hrs or 1 yr | “Every 7500 L (2000 US gal) of Fuel or 250 Service Hours or 1 Year ... Auxiliary Water Pump - Inspect” — manufacturer, oxfordyachtagency.com |
| Engine pencil zincs | 50 hrs | “Every 1500 L (400 US gal) of Fuel or 50 Service Hours ... Zinc Rods - Inspect/Replace” — manufacturer, oxfordyachtagency.com |
| Valve clearance check / adjust | 2,000 hrs | “First 7500 L (2000 US gal) of Fuel or 250 Service Hours ... Engine Valve Lash - Inspect/Adjust” — manufacturer, oxfordyachtagency.com |
| Coolant replacement & freeze-point test Cat DEAC / conventional coolant | 1,000 hrs or 2 yrs | “Every 30 000 L (8000 US gal) of Fuel or 1000 Service Hours or 2 Years ... Cooling System Coolant (DEAC) - Change” — manufacturer, oxfordyachtagency.com |
| Coolant replacement & freeze-point test Cat ELC (extended life coolant) | 6,000 hrs or 4 yrs | “Every 182 000 L (48 000 US gal) of Fuel or 6000 Service Hours or 4 Years ... Cooling System Coolant (ELC) - Change” — manufacturer, oxfordyachtagency.com |
| Turbocharger inspection | 1,000 hrs or 2 yrs | “Every 30 000 L (8000 US gal) of Fuel or 1000 Service Hours or 2 Years ... Aftercooler Core - Clean/Test” — manufacturer, oxfordyachtagency.com |
| Turbocharger inspect | 1,000 hrs or 2 yrs | “Every 30 000 L (8000 US gal) of Fuel or 1000 Service Hours or 2 Years ... Turbocharger - Inspect” — manufacturer, oxfordyachtagency.com |
| Heat exchanger & oil cooler cleaning | 2,000 hrs | “Every 60 000 L (16 000 US gal) of Fuel or 2000 Service Hours ... Heat Exchanger - Inspect” — manufacturer, oxfordyachtagency.com |
| Drive belts inspect / replace | 250 hrs or 1 yr | “Every 7500 L (2000 US gal) of Fuel or 250 Service Hours or 1 Year ... Belt - Inspect” — manufacturer, oxfordyachtagency.com |
| Fuel injection timing check | 2,000 hrs | “First 7500 L (2000 US gal) of Fuel or 250 Service Hours ... Fuel Injection Timing - Check” — manufacturer, oxfordyachtagency.com |
| Thermostat (coolant temperature regulator) replace | 3,000 hrs or 2 yrs | “Every 91 000 L (24 000 US gal) of Fuel or 3000 Service Hours or 2 Years ... Cooling System Water Temperature Regulator -” — manufacturer, oxfordyachtagency.com |
| Sea water strainer clean/inspect | 250 hrs or 1 yr | “Every 7500 L (2000 US gal) of Fuel or 250 Service Hours or 1 Year ... Sea Water Strainer - Clean/Inspect” — manufacturer, oxfordyachtagency.com |
| Jacket water pump inspect | 250 hrs or 1 yr | “Every 7500 L (2000 US gal) of Fuel or 250 Service Hours or 1 Year ... Water Pump - Inspect” — manufacturer, oxfordyachtagency.com |
| Coolant SCA test/add | 250 hrs or 1 yr | “Every 7500 L (2000 US gal) of Fuel or 250 Service Hours or 1 Year ... Cooling System Supplemental Coolant Additive (SCA)” — manufacturer, oxfordyachtagency.com |
| Hoses and clamps inspect/replace | 250 hrs or 1 yr | “Every 7500 L (2000 US gal) of Fuel or 250 Service Hours or 1 Year ... Hoses and Clamps - Inspect/Replace” — manufacturer, oxfordyachtagency.com |
| Crankcase breather clean | 250 hrs or 1 yr | “Every 7500 L (2000 US gal) of Fuel or 250 Service Hours or 1 Year ... Engine Crankcase Breather - Clean” — manufacturer, oxfordyachtagency.com |
Service part numbers (3)
| Oil filter | Sources disagree: 1R-0658 / 324-2598 | “**Oil Filter** **CAT 1R-0658** | 3126B C7 3306 3304 3116 C4.2 3046 3066” — dealer, marineenergy.com.au · “Caterpillar 324-2598 Advanced Efficiency 3116 and 3126 Diesel Engine Oil Filter” — dealer, marineengineparts.com |
| Fuel filter | Caterpillar 1R-0751 Also: Baldwin BF7632, Fleetguard FF5324, WIX 33626 |
“Caterpillar 1R-0751 Advanced Efficiency 3116 and 3126 Diesel Engine Fuel Filter” — dealer, marineengineparts.com · “the secondary fuel filter Cat specifies for the 3114, 3116, 3126/B/E, C7, and C9 family” — dealer, allprodiesel.net |
| Raw-water impeller keyway-shaft Sherwood seawater pump |
Sherwood 17000K | “| **Impeller** | 17000K KEY WAY |” — dealer, marineenergy.com.au · “Caterpillar Marine Engines ... Common applications include: ... CAT 3116” — dealer, marisolmarine.com |
| Zinc / anode | Caterpillar 6L-2283 × 3 | “**Anode kit CAT3116** | 3 x 6L2283 2 x 6L2281 1 x 6L3104” — dealer, marineenergy.com.au · “Zinc Anode for Caterpillar Marine Engines 6L2283 NPT: 1/4”” — dealer, dieselpro.com |
From the engine maker’s parts lists, or two independent parts dealers. Numbers change with serial number and get superseded — check yours before ordering.
Caterpillar 3126 / 3126B parts: good
Factory optional engine — you entered “Caterpillar 3126”
Electronically controlled HEUI engine that evolved into the C7 (around 2003); Cat dealers support it and released upgraded aftercoolers/cores. Aftercooler replacement is costly (owners cite thousands per engine).
Parts sources: Diesel Pro Power
Common problems (3)
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Aftercooler leaking seawater into the engine cooling
Early 3126s had seawater-cooled aftercoolers that corroded from dissimilar metals and could leak salt water into the engine; Cat later offered upgraded aftercoolers, and surveyors check for this specifically.trawlerforum.com · samsmarine.com · clubsearay.com
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HEUI pump, hose and spool valve problems fuel
The high-pressure oil (HEUI) pump can fail, early 3126B high-pressure hoses were prone to failure (a steel-tube conversion exists), and sticky injector spool valves cause hard starting or rough running.trawlerforum.com
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Power loss and sooting engine
Owners troubleshoot engines that will not reach rated rpm and soot heavily at cruise, checking air filters, aftercooler condition, turbo and injectors.facebook.com
Maker’s service schedule (18)
| Engine oil & filter change | 250 hrs or 1 yr | “Every 7500 L (2000 US gal) of Fuel or 250 Service Hours or 1 Year ... Engine Oil and Filter - Change” — manufacturer, oxfordyachtagency.com |
| Fuel filters & water separator | 250 hrs or 1 yr | “Every 7500 L (2000 US gal) of Fuel or 250 Service Hours or 1 Year ... Fuel System Primary Filter/Water Separator Element” — manufacturer, oxfordyachtagency.com |
| Raw-water pump impeller | 250 hrs or 1 yr | “Every 7500 L (2000 US gal) of Fuel or 250 Service Hours or 1 Year ... Auxiliary Water Pump - Inspect” — manufacturer, oxfordyachtagency.com |
| Engine pencil zincs | 50 hrs | “Every 1500 L (400 US gal) of Fuel or 50 Service Hours ... Zinc Rods - Inspect/Replace” — manufacturer, oxfordyachtagency.com |
| Valve clearance check / adjust | 2,000 hrs | “First 7500 L (2000 US gal) of Fuel or 250 Service Hours ... Engine Valve Lash - Inspect/Adjust” — manufacturer, oxfordyachtagency.com |
| Coolant replacement & freeze-point test Cat DEAC / conventional coolant | 1,000 hrs or 2 yrs | “Every 30 000 L (8000 US gal) of Fuel or 1000 Service Hours or 2 Years ... Cooling System Coolant (DEAC) - Change” — manufacturer, oxfordyachtagency.com |
| Coolant replacement & freeze-point test Cat ELC (extended life coolant) | 6,000 hrs or 4 yrs | “Every 182 000 L (48 000 US gal) of Fuel or 6000 Service Hours or 4 Years ... Cooling System Coolant (ELC) - Change” — manufacturer, oxfordyachtagency.com |
| Turbocharger inspection | 1,000 hrs or 2 yrs | “Every 30 000 L (8000 US gal) of Fuel or 1000 Service Hours or 2 Years ... Aftercooler Core - Clean/Test” — manufacturer, oxfordyachtagency.com |
| Turbocharger inspect | 1,000 hrs or 2 yrs | “Every 30 000 L (8000 US gal) of Fuel or 1000 Service Hours or 2 Years ... Turbocharger - Inspect” — manufacturer, oxfordyachtagency.com |
| Heat exchanger & oil cooler cleaning | 2,000 hrs | “Every 60 000 L (16 000 US gal) of Fuel or 2000 Service Hours ... Heat Exchanger - Inspect” — manufacturer, oxfordyachtagency.com |
| Drive belts inspect / replace | 250 hrs or 1 yr | “Every 7500 L (2000 US gal) of Fuel or 250 Service Hours or 1 Year ... Belt - Inspect” — manufacturer, oxfordyachtagency.com |
| Fuel injection timing check | 2,000 hrs | “First 7500 L (2000 US gal) of Fuel or 250 Service Hours ... Fuel Injection Timing - Check” — manufacturer, oxfordyachtagency.com |
| Thermostat (coolant temperature regulator) replace | 3,000 hrs or 2 yrs | “Every 91 000 L (24 000 US gal) of Fuel or 3000 Service Hours or 2 Years ... Cooling System Water Temperature Regulator -” — manufacturer, oxfordyachtagency.com |
| Sea water strainer clean/inspect | 250 hrs or 1 yr | “Every 7500 L (2000 US gal) of Fuel or 250 Service Hours or 1 Year ... Sea Water Strainer - Clean/Inspect” — manufacturer, oxfordyachtagency.com |
| Jacket water pump inspect | 250 hrs or 1 yr | “Every 7500 L (2000 US gal) of Fuel or 250 Service Hours or 1 Year ... Water Pump - Inspect” — manufacturer, oxfordyachtagency.com |
| Coolant SCA test/add | 250 hrs or 1 yr | “Every 7500 L (2000 US gal) of Fuel or 250 Service Hours or 1 Year ... Cooling System Supplemental Coolant Additive (SCA)” — manufacturer, oxfordyachtagency.com |
| Hoses and clamps inspect/replace | 250 hrs or 1 yr | “Every 7500 L (2000 US gal) of Fuel or 250 Service Hours or 1 Year ... Hoses and Clamps - Inspect/Replace” — manufacturer, oxfordyachtagency.com |
| Crankcase breather clean | 250 hrs or 1 yr | “Every 7500 L (2000 US gal) of Fuel or 250 Service Hours or 1 Year ... Engine Crankcase Breather - Clean” — manufacturer, oxfordyachtagency.com |
Service part numbers (3)
| Oil filter | Sources disagree: 1R-0658 / 324-2598 | “**Oil Filter** **CAT 1R-0658** | 3126B C7 3306 3304 3116 C4.2 3046 3066” — dealer, marineenergy.com.au · “Caterpillar 324-2598 Advanced Efficiency 3116 and 3126 Diesel Engine Oil Filter” — dealer, marineengineparts.com |
| Fuel filter | Caterpillar 1R-0751 Also: Baldwin BF7632, Fleetguard FF5324, WIX 33626 |
“Caterpillar 1R-0751 Advanced Efficiency 3116 and 3126 Diesel Engine Fuel Filter” — dealer, marineengineparts.com · “the secondary fuel filter Cat specifies for the 3114, 3116, 3126/B/E, C7, and C9 family” — dealer, allprodiesel.net |
| Raw-water impeller keyway-shaft Sherwood seawater pump |
Sherwood 17000K | “| **Impeller** | 17000K KEY WAY |” — dealer, marineenergy.com.au · “Caterpillar Marine Engines ... Common applications include: ... CAT 3126 / 3126B” — dealer, marisolmarine.com |
| Zinc / anode heat-exchanger anode |
Caterpillar 6L-2283 × 2 | “Replaces Caterpillar 6L2283, / 6L2282 (With the plug) Used on Caterpillar 3126, 3208 diesel marine engines. Qty 2 on Hea” — dealer, marineenergy.com.au · “Zinc Anode for Caterpillar Marine Engines 6L2283 NPT: 1/4”” — dealer, dieselpro.com |
From the engine maker’s parts lists, or two independent parts dealers. Numbers change with serial number and get superseded — check yours before ordering.
Cummins 6BT / 6BTA 5.9 parts: good
Factory optional engine — you entered “Cummins 6BTA 5.9”
Mechanically injected 5.9 L inline six from the Cummins B-series truck/industrial family, so base-engine parts are everywhere. Cummins still sells factory ReCon (remanufactured) marine 6BT/6BTA engines (152–210 hp ratings) with a 2-year/2000-hour warranty. Seaboard Marine is the best-known marine specialist, selling aftercooler/heat-exchanger service kits, upgraded raw water pumps and technical guidance; TAD also sells Cummins packages.
Parts sources: Seaboard Marine, Cummins (ReCon 6BT/6BTA), Diesel Pro Power
Common problems (2)
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Aftercooler corrosion letting seawater into the intake cooling
On the turbo-aftercooled 6BTA the seawater-cooled aftercooler core has vertical tubes and an aluminum housing that corrodes from condensate; a leak can put salt water into the cylinders and wreck the engine. Owners pull, clean, grease and pressure-test the core every few years and fit new O-rings.trawlerforum.com · sbmar.com
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Heat exchanger and aftercooler service cooling
Routine seawater-side service (O-rings, gaskets, zincs) is a recurring owner job; kits are sold for it and refilling coolant without trapping air is a common question.sbmar.com · sbmar.com
Service part numbers (5)
| Oil filter | Cummins 3937743 | “| Oil Filter | 3937743 |” — dealer, marineenergy.com.au · “Cummins Oil Filter 3937743 Spin-on type, 3.66" outside diameter, 6.95" height” — dealer, dieselpro.com |
| Fuel filter 6BT 5.9 210 hp (CPL 742) |
Fleetguard FF5052 Replaces FF42000, FS1251 |
“on-engine fuel filter with drain for all 6BT 210 B’s (CPL 742). Replaces the FF42000, FS1251.” — dealer, sbmar.com · “Cummins 6BT Fuel Filter 3931063 FF5052” — dealer, marineenergy.com.au |
| Fuel filter late 6BTA (also late 4BTA and 6CTA) |
Fleetguard FF5285 | “Fleetguard FF5285 Fuel Filter – late 4BTA 6BTA and 6CTA’s” — dealer, sbmar.com · “Cummins 6BTA Fuel Filter 3890017 FF5285 ... suits late model Cummins 6BTA's, 6CTA8.3-M” — dealer, marineenergy.com.au |
| Raw-water impeller seawater pump with 1-1/4 in hose ports (Sherwood M70/M71 type, early 4BT/6BT) |
Sherwood 10615K | “Seawater Pump Impeller | **1-1/4" PORTS** 3908220 10615K” — dealer, marineenergy.com.au · “Cummins Marine Water Pump Impeller 10615K 2 9/16" diameter, 1 5/8" length” — dealer, dieselpro.com |
| Raw-water impeller keyway-shaft pump, 2 in inlet / 1-3/4 in outlet, 11° offset flange (e.g. P1716/P1730 on 6BTA) |
Sherwood 17000K | “**2" inlet & 1-3/4" outlet ports with 11° OFFSET flange** 17000K” — dealer, marineenergy.com.au · “Cummins Impeller for Key Shaft 17000K” — dealer, dieselpro.com |
From the engine maker’s parts lists, or two independent parts dealers. Numbers change with serial number and get superseded — check yours before ordering.
Yanmar 6LY (6LY2, 6LY3, 6LYA-STP) parts: good
Factory optional engine — you entered “Yanmar 6LY”
Current Yanmar dealer support; cooler service is costly (one owner was quoted about $8,000 for a full cooler service).
Parts sources: Mack Boring & Parts (Yanmar distributor)
Common problems (2)
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Aftercooler, heat exchanger and oil cooler service cooling
Owners service the aftercooler, coolant heat exchanger and oil cooler about every three years in salt water; neglect shows as green corrosion at seams, corroded O-ring grooves and seized bolts, and can require a new cooler.trawlerforum.com
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Turbo oil leaks and lag exhaust
Turbos leaking oil into the intake and aftercooler, and slow turbo response with smoke, are recurring 6LYA complaints.downeastboatforum.com · justanswer.com
Maker’s service schedule (21)
| Engine oil & filter change 6LY3-ETP / 6LY3-STP / 6LY3-UTP (6LY3 manual) | 250 hrs or 1 yr | “Change the engine oil after the first 50 hours of operation and then at every 250 hours thereafter.” — manufacturer, nhmr.nl |
| Fuel filters & water separator 6LY3-ETP / 6LY3-STP / 6LY3-UTP (6LY3 manual) | 250 hrs or 1 yr | “When the engine is operated on light diesel oil, replace the fuel filter element every 250 hours or one year of operatio” — manufacturer, nhmr.nl |
| Drain fuel filter and fuel/water separator 6LY3-ETP / 6LY3-STP / 6LY3-UTP (6LY3 manual) | 50 hrs or 1 mo | “Perform the following maintenance every 50 hours or one month of operation, whichever comes first. Drain Fuel Filter and” — manufacturer, nhmr.nl |
| Raw-water pump impeller 6LY3-ETP / 6LY3-STP / 6LY3-UTP (6LY3 manual) | 500 hrs or 2 yrs | “Perform the following maintenance every 500 hours or two years of operation, whichever comes first. Replace Seawater Pum” — manufacturer, nhmr.nl |
| Engine pencil zincs 6LY3-ETP / 6LY3-STP / 6LY3-UTP (6LY3 manual) | 250 hrs or 1 yr | “Perform the following maintenance every 250 hours or one year of operation, whichever comes first. ... Replace the Anode” — manufacturer, nhmr.nl |
| Coolant replacement & freeze-point test 6LY3-ETP / 6LY3-STP / 6LY3-UTP (6LY3 manual) | 250 hrs or 1 yr | “Perform the following maintenance every 250 hours or one year of operation, whichever comes first. ... Replace Engine Co” — manufacturer, nhmr.nl |
| Air filter / intake silencer 6LY3-ETP / 6LY3-STP / 6LY3-UTP (6LY3 manual) | 250 hrs or 1 yr | “Perform the following maintenance every 250 hours or one year of operation, whichever comes first. ... Clean the Air Int” — manufacturer, nhmr.nl |
| Exhaust mixing elbow inspection 6LY3-ETP / 6LY3-STP / 6LY3-UTP (6LY3 manual) | 250 hrs or 1 yr | “Perform the following maintenance every 250 hours or one year of operation, whichever comes first. ... Clean the Exhaust” — manufacturer, nhmr.nl |
| Turbocharger inspection 6LY3-ETP / 6LY3-STP / 6LY3-UTP (6LY3 manual) | 250 hrs or 1 yr | “Perform the following maintenance every 250 hours or one year of operation, whichever comes first. ... Clean the Turboch” — manufacturer, nhmr.nl |
| Valve clearance check / adjust 6LY3-ETP / 6LY3-STP / 6LY3-UTP (6LY3 manual) | 1,000 hrs or 4 yrs | “Perform the following maintenance every 1000 hours or four years of operation, whichever comes first. ... Adjust Intake” — manufacturer, nhmr.nl |
| Injector test / service 6LY3-ETP / 6LY3-STP / 6LY3-UTP (6LY3 manual) | 250 hrs or 1 yr | “Perform the following maintenance every 250 hours or one year of operation, whichever comes first. Check Fuel Injector S” — manufacturer, nhmr.nl |
| Drive belts inspect / replace 6LY3-ETP / 6LY3-STP / 6LY3-UTP (6LY3 manual) | 50 hrs or 1 mo | “Perform the following maintenance every 50 hours or one month of operation, whichever comes first. ... Adjust Alternator” — manufacturer, nhmr.nl |
| Replace flexible engine mounts 6LY3-ETP / 6LY3-STP / 6LY3-UTP (6LY3 manual) | 1,000 hrs or 4 yrs | “Be sure to replace the Yanmar flexible engine mounts every 1000 hours or 4 years, whichever comes first.” — manufacturer, nhmr.nl |
| Heat exchanger & oil cooler cleaning 6LY3-ETP / 6LY3-STP / 6LY3-UTP (6LY3 manual) | 2,000 hrs or 8 yrs | “Perform the following maintenance every 2000 hours or eight years of operation, whichever comes first. Overhaul and Chec” — manufacturer, nhmr.nl |
| Engine oil & filter change 6LYA-STP / 6LY2A-STP (older Yanmar Diesel Engine Co. manual) | 250 hrs or 1 yr | “4.3.4 Inspection Every 250 Hrs.(or 1 yr.) ... Replace the engine lube oil every 250 hours. Replace the lube oil filter,” — manufacturer, s2b4aa72b8b1c7323.jimcontent.com |
| Fuel filters & water separator 6LYA-STP / 6LY2A-STP (older Yanmar Diesel Engine Co. manual) | 250 hrs or 1 yr | “4.3.4 Inspection Every 250 Hrs.(or 1 yr.)” — manufacturer, s2b4aa72b8b1c7323.jimcontent.com |
| Engine pencil zincs 6LYA-STP / 6LY2A-STP (older Yanmar Diesel Engine Co. manual) | 250 hrs or 1 yr | “4.3.4 Inspection Every 250 Hrs.(or 1 yr.)” — manufacturer, s2b4aa72b8b1c7323.jimcontent.com |
| Turbocharger inspection 6LYA-STP / 6LY2A-STP (older Yanmar Diesel Engine Co. manual) | 250 hrs or 1 yr | “4.3.4 Inspection Every 250 Hrs.(or 1 yr.)” — manufacturer, s2b4aa72b8b1c7323.jimcontent.com |
| Drive belts inspect / replace 6LYA-STP / 6LY2A-STP (older Yanmar Diesel Engine Co. manual) | 500 hrs or 2 yrs | “4.3.5 Inspection Every 500 Hrs. (or 2 yrs.) 1 Inspection of AIternator V-Belt Tension” — manufacturer, s2b4aa72b8b1c7323.jimcontent.com |
| Raw-water pump impeller 6LYA-STP / 6LY2A-STP (older Yanmar Diesel Engine Co. manual) | 2,000 hrs | “(Note) The impeller must be replaced periodically (every 2000 hours).” — manufacturer, s2b4aa72b8b1c7323.jimcontent.com |
| Heat exchanger & oil cooler cleaning 6LYA-STP / 6LY2A-STP (older Yanmar Diesel Engine Co. manual) | 2,000 hrs | “4.3.7 Inspection Every 2000 Hrs. (1) Cleaning the Cooling Water System and Inspecting & Adjusting Parts” — manufacturer, s2b4aa72b8b1c7323.jimcontent.com |
Service part numbers (6)
| Oil filter | Yanmar 119593-35100-12 Replaces 119593-35100, 119593-35110 |
“119593-35100-12 Oil Filter” — dealer, oldportmarine.com · “It fits Yanmar 6LY-UTE, 6LY3-ETP, 6LYA-STE, 6LY2A engines. Cross Reference: 11959335110 119593-35110 119593-35100” — dealer, deltadieselparts.com |
| Fuel filter | Yanmar 41650-502330-12 Replaces 41650-502330 |
“41650-502330-12 Fuel Filter” — dealer, oldportmarine.com · “It fits Yanmar 6LY-UTE, 6LY2-STE, 6LY2A-STP, 6LY3-ETP, 6LY3-UTP, 6LYA-STP, 6LYA-STE, 6LY2A engines.” — dealer, deltadieselparts.com |
| Raw-water impeller | Yanmar 119574-42530 | “119574-42530 Impeller Box Kit” — dealer, oldportmarine.com · “compatible with engine models 6LY2-ST, 6LY2-WDT, 6LYA-STE, and 6LY2A-STP” — dealer, shop.marinedieselinc.com |
| Drive belt 6LY, 6LYA, 6LY2(A) |
Yanmar 119593-42280 | “119593-42280 Belt” — dealer, oldportmarine.com · “It fits Yanmar 6LY2A-STP, 6LY2A engines.” — dealer, deltadieselparts.com |
| Air filter | Yanmar 119593-18880 | “119593-18880 Air Element” — dealer, oldportmarine.com · “119593-18880 Air Filter Foam Element for Yanmar 6CX 4CX 6LY 6LP 6HY 6KY 6HYM” — dealer, jlmmarine.com |
| Zinc / anode all 6LY except 6LY3 |
Yanmar 119574-44150 × 4 | “119574-18790 (1) & 119574-44150 (4) Zincs” — dealer, oldportmarine.com · “Oil cooler and heat exchanger zinc anode for Yanmar 4LHA's, 6LP's and all 6LY's (except 6LY3)” — dealer, boatzincs.com |
From the engine maker’s parts lists, or two independent parts dealers. Numbers change with serial number and get superseded — check yours before ordering.
Model sources (9)
hmy.com · denisonyachtsales.com · trawlerforum.com · murrayyachtsales.com · yachtsurvey.com · trawlerforum.com · shellerina.com · shellerina.com · curtisstokes.net
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Other Mainship models
- Mainship 34 Diesel Cruiser (34 Trawler, 1978) 1978–1982
- Mainship 34 Pilot 1998–2008
- Mainship 34 Trawler (2005) 2005–2009
- Mainship 400 / 414 Trawler 2003–2012
- Mainship 430 Trawler 1999–2006
Researched from public sources. Spotted an error? The sources are listed above — tell us what they got wrong.