Mainship 34 Diesel Cruiser (34 Trawler, 1978)

Built 1978–1982 by Mainship

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About the Mainship 34 Diesel Cruiser (34 Trawler, 1978)

Researched from public sources for this model. Any individual boat may have been modified or repowered — confirm before relying on any figure.

Illustration of a Mainship 34 Diesel Cruiser (34 Trawler, 1978) — **Illustration, not a photo of this model.** AI-generated illustration of a typical single-engine sedan trawler.

Built: 1978–1982
Builder: Mainship
Length: 34 ft
Waterline: 30.17 ft
Beam: 11.92 ft
Draft: 2.83 ft
Displacement: 14,000 lb
Hull: fiberglass
Hull / keel: semi-displacement
Propulsion: inboard
Fuel: 220 gal
Water: 50 gal
Holding: 30 gal

Tank capacities — where the figures come from

Fuel 220 gal
“220 gallons fuel” — review, soundingsonline.com · “Fuel: 220 gals.” — spec database (1978-1982), 34mainship.com

A Soundings used-boat review and an owner's website for their boat agree; no builder document could be checked.
Water 50 gal
“50 gallons water” — review, soundingsonline.com · “Water: 50 gals” — spec database (1978-1982), 34mainship.com · “40 to 50 gallon water supply (depending on year and model)” — search excerpt, denisonyachtsales.com

A broker's review says 40–50 gal depending on year and model; 50 is the usual figure.
Holding 30 gal
No holding figure found; a Soundings owner profile only calls the original tank small.
Water heater unknown
“full water system Hot/cold” — search excerpt (1979), trawlerforum.com

Broker listings mention hot water but give no heater size or brand; the builder brochure on the owners' site couldn't be checked.

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 unknown
“Bow thruster” — broker listing (1979), boatsdata.com · “1981 Mainship trawler 34 feet ... Features Vetus bow thruster” — search excerpt (1981), powerboatlistings.com

No builder equipment list was found. Two separate boats (1979 and 1981, the 1981 one a Vetus) have bow thrusters, but neither says whether it was factory-fitted or added.
Stern thruster unknown
No source mentions a stern thruster.
Steering unknown
No builder or review source was found; a single 1978 for-sale-by-owner ad mentions hydraulic steering.

Thrusters and steering are often replaced — check the units on your boat before ordering parts.

Mainship's original model, usually called the Mainship 34 Trawler. Solid fiberglass semi-displacement hull with full-length keel. Single 160 hp Perkins diesel cruises 10-11 knots (about 6 gph) or 7 knots at about 2 gph. Single-stateroom layout with standard lower helm.

Engines fitted

Perkins T6.354 (6-cyl turbo) — 160 hp, diesel, single standard
Base engine on all sources; forum owners say later Mark II boats carried the updated T6.3544 at 165 hp.

Sources: hmy.com · soundingsonline.com · denisonyachtsales.com · trawlerforum.com
Perkins T6.3544 (200 hp) — 200 hp, diesel, single factory option
A 200 hp Perkins was added as an option in 1980.

Sources: denisonyachtsales.com · soundingsonline.com · soundingsonline.com · trawlerforum.com
Mitsubishi 6-cyl diesel — 200 hp, diesel, single factory option
Forum owners say a few boats were built with a 200 hp Mitsubishi (and a few with an International V8); single source only.

Sources: trawlerforum.com
Volvo Penta TAMD40A — 135 hp, diesel, single common repower
Mentioned by owners as a repower, along with unspecified Cummins engines; single source.

Sources: trawlerforum.com

Boats of the same model can differ — check which engines yours actually has before ordering parts.

Generator

“165 hp perkins, 4 kw onan generator” — search excerpt (1979), boatexportusa.com · “Onan generator, new carpets” — search excerpt (1979), trawlerforum.com · “original air conditioner, original stove as well as the original generator” — search excerpt (1979), boats-from-usa.com

Three separate 1979 boats for sale have a generator; two say Onan (one 4 kW, one unsized) and a third calls its generator original, which hints at a dealer or factory fit, but no builder list confirms whether it was standard or optional.

Known problems for this model

Wet balsa-cored foredeck deck
Moisture in the balsa-cored foredeck is a recognized problem on this model; sound and moisture-meter the foredeck and flybridge deck and rebed deck hardware.
hmy.com

Engines & parts

Perkins 6.354 / T6.354 parts: limited

Factory standard engine — you entered “Perkins T6.354 (6-cyl turbo)”

Inline six of about 354 cu in, naturally aspirated or turbocharged (T6.354.4 around 240 hp). TAD still builds complete marinized 6.354 packages and sells parts; owners on the Hatteras forum report some parts for older versions getting harder to find and marine cooling parts (multi-cooler, heat exchangers) being expensive.

Parts sources: Trans Atlantic Diesels (TAD), Perkins official parts shop

Common problems (2)

Persistent oil leaks engine
Owners describe the 6.354 as a habitual oil leaker because of its seals, meaning regular bilge cleanup.
samsmarine.com
Multi-cooler and heat exchanger costs cooling
Mixed metals in the raw water circuit mean frequent heat exchanger and gasket work, and the turbo model's multi-cooler is a known weak and costly part.
samsmarine.com

Maker’s service schedule (9)

Engine oil & filter change general periods, all applications (1970 workshop manual)	200 hrs or 4 mo	“Every 5,000 Miles (7,500 km), 200 Hours or 4 Months — Drain and renew engine lubricating oil. Renew lubricating oil filt” — manufacturer, archive.org
Turbocharger inspection T6.354 — turbocharger oil filter (where fitted)	200 hrs or 4 mo	“Turbocharged Engines. Renew turbocharger lubricating oil filter element (where fitted).” — manufacturer, archive.org
Turbocharger inspection T6.354 — turbocharger cleaning	800 hrs	“Every 20,000 Miles (30,000 km), 800 Hours ... Turbocharged Engines. Clean turbocharger impeller, diffuser and oil drain” — manufacturer, archive.org
Drive belts inspect / replace general periods, all applications (1970 workshop manual)	200 hrs or 4 mo	“Every ... 200 Hours or 4 Months ... Check drive belt tension.” — manufacturer, archive.org
Clean fuel water trap general periods, all applications (1970 workshop manual)	200 hrs or 4 mo	“Every ... 200 Hours or 4 Months ... Clean water trap.” — manufacturer, archive.org
Clean fuel lift pump gauze strainer; check hoses and clips general periods, all applications (1970 workshop manual)	400 hrs or 1 yr	“Every 10,000 Miles (15,000 km), 400 Hours or 12 months — Clean lift pump gauze strainer. ... Check hoses and clips.” — manufacturer, archive.org
Air filter / intake silencer dry-type air cleaner	800 hrs	“Every 20,000 Miles (30,000 km), 800 Hours ... Clean element of dry type air cleaner or renew.” — manufacturer, archive.org
Injector test / service general periods, all applications (1970 workshop manual)	2,400 hrs	“Every 60,000 Miles (90,000 km), 2,400 Hours ... Service atomisers.” — manufacturer, archive.org
Valve clearance check / adjust general periods, all applications (1970 workshop manual)	2,400 hrs	“Every 60,000 Miles (90,000 km), 2,400 Hours ... Check and adjust tappets.” — manufacturer, archive.org

Service part numbers (7)

Oil filter T6.354 / HT6.354 (Lancing); go2marine fit list covers 6.354M as well	Perkins 2654403	“Oil Filter (Length 130mm) - 2654403” — dealer, lancingmarine.com · “Fits: Perkins - ... 6.354, 6.354M, A6.354, H6.354, H6.354M, HT6.354, HT6.354M, T6.354, T6.354M ... Replaces: Perkins 265” — dealer, go2marine.com
Fuel filter	Perkins 4326658 Replaces 26561117 Also: Delphi (CAV) 296	“A genuine Perkins 6.354 fuel filter - OE Part No. 4326658” — dealer, parts4engines.com · “Fuel Filter (296) Was 26561117 Now 4326658” — dealer, lancingmarine.com
Raw-water impeller Jabsco 9990-41 (or obsolete 9990-21) 3/4-inch barrel pump	Jabsco 1210-0001	“T / H / HT 6.354 M 9990-41 040 3/4" NPT Barrel SK268 3298 1210-0001” — manufacturer, marineengine.com · “Sea Water Pump - 9990-41” — dealer, lancingmarine.com
Raw-water impeller Jabsco 9700-series 1-inch flanged pump (9700-01, -04, -141, -151)	Jabsco 17937-0001	“6.354 9700-01 080 1" Flanged Flange SK238 890 17937-0001” — manufacturer, marineengine.com
Raw-water pump kit Jabsco 9990-41 pump	Jabsco SK268	“T / H / HT 6.354 M 9990-41 040 3/4" NPT Barrel SK268 3298 1210-0001” — manufacturer, marineengine.com
Raw-water pump kit Jabsco 9700-01 pump	Jabsco SK238	“6.354 9700-01 080 1" Flanged Flange SK238 890 17937-0001” — manufacturer, marineengine.com
Raw-water pump kit Jabsco 9700-151 / 9700-04 pump	Jabsco SK238-01	“6.3543 M 9700-04 080 1" Flanged Flange SK238-01 3101 17937-0001” — manufacturer, marineengine.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 (7)

hmy.com · soundingsonline.com · denisonyachtsales.com · trawlerforum.com · soundingsonline.com · 34mainship.com · boatsdata.com

Other Mainship models

Researched from public sources. Spotted an error? The sources are listed above — tell us what they got wrong.