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Model profile · for Great Loop buyers
Mainship 43 Sedan Trawler
What the published record establishes about this model, what owners report,
and the questions worth asking while a boat is still a listing. This page is about the
MODEL — a specific hull always gets its own homework.
A comfortable semi-displacement sedan trawler whose risk profile hinges almost entirely on which engine it was built with — the 440hp Yanmar being the one to scrutinize.
The Mainship 43 (part of the Mainship 430 series, built roughly 1999–2006/07) is a semi-displacement sedan trawler that will cruise economically at hull speed yet has enough power to plane. It was offered with several distinct powerplants over the run — Cat 3126, Yanmar 370hp, Yanmar 440hp, and rarely Cummins 8.3L — so many of its known issues are engine-configuration-specific. The single most important thing a buyer can establish is exactly which engine and layout their candidate hull carries. It is a capable Loop boat, but air draft and engine access are the two items that repeatedly surface in owner discussion.
How to read this: 🟢 Fact = confirmed against a document, spec sheet,
or owner. Everything else — Claim, Pattern, Question, Context — is not yet
verified: things to check, not settled truth. Sources are linked where published.
Engine access
CLAIM
Engine room is tight for major work
Owners report the engine space is cramped: roughly 29" of horizontal clearance against 28" engine mounts, and because the engine isn't centered the door opening makes removal awkward. A recurring Mainship complaint is that some basic maintenance or part replacement can require cutting hatches. This is a hull/layout property, not an engine trait.
src:
Trawler Forum — "Need advise on engine removal from Mainship 430" and "2003 Mainship 430" threads
Your move: During survey, have the surveyor confirm access to filters, heat exchangers, aftercoolers, and pumps without removing structure; factor labor difficulty into service-cost estimates.
Reading the boat
QUESTION
If Cummins 8.3L powered — what's the service and repower history?
Some later/rarer 43s were fitted with twin Cummins 8.3L (buyers report ~480hp a side, around a 2006 model). Substantial owner failure reports specific to Cummins-powered 430s were not found — this is 'not documented,' not 'proven trouble-free.' A Cummins in what is often a Yanmar/Cat boat also raises the question of whether it's a repower.
src:
Trawler Forum — "Mainship 430 aft" thread
Your move: If Cummins-powered, ask whether this was factory or a repower, and get the full service history and any repower documentation in writing.
Air draft
CLAIM
Air draft varies widely with mast, arch, antennas and canvas
Owner-measured air drafts on this model range widely depending on equipment — some measured under 19', others near 20' after adding gear, and many 430s in the field have no hinged/lowering mast. Radar posts, satellite antennas, convertible tops and enclosures all change the figure. This spread is exactly why the model needs individual measurement: two identically named boats can differ by more than a foot, which affects access to lower-clearance Loop routes.
src:
Trawler Forum — "Air draft of a 430?" thread; YachtWorld — "Mainship 43 Trawler"
Your move: Measure your specific boat's air draft at a known load state, and identify exactly what (mast, antennas, arch, canvas) can be removed or lowered and how much each saves.
CONTEXT
Load and water density shift the measured height
Owners note a boat sits lower in fresh water than salt and lower when lightly loaded, so air draft should be assessed near the load state you'll actually run. One owner deliberately measured with a half-load of fuel before a low-clearance canal.
src:
Trawler Forum — "Air draft of a 430?" thread
Range & fuel burn
CONTEXT
Expect economical burn at hull speed with the 370hp Yanmars
Owner reports with twin 370hp Yanmars: roughly 8.5 knots at 1600 rpm burning just under 4 gph total, and about 9 knots near hull speed at 1800 rpm averaging ~5 gph including generator/heater. The 440hp boats pushed harder plane and burn far more — owners advise keeping cruising rpm at 2,800 or less, burning ~20–25 gph for both engines at that rpm. Slow-cruise range is comfortable; planing range is short.
src:
Trawler Forum — owner fuel-burn reports
Engines
The engines research — factory options, tested performance,
and the engine-specific questions our members' dossiers carry — is part of the
full profile inside the product. It travels with every dossier and survey brief
built on this model.