← The model library
Model profile · for Great Loop buyers
Jefferson 42 Sundeck
The published record on this model and what owners report, with the
questions worth asking while a boat is still a listing. This page covers the model.
Every boat still needs its own homework.
The published record
| Length overall | 41.67 ft |
| Beam | 14.25 ft |
| Draft | 3'7" |
| Fuel | 350 gal |
| Water | 200 gal |
| Holding | 50 gal |
Source: PowerBoat Guide (HMY), Jefferson 42 Sundeck (1986 to 1995).
If a listing disagrees with these numbers, the listing may still be right. Settle the
difference before it costs you.
A roomy Taiwan sundeck with a 3'7" draft and no published air draft. Leaks and the original black iron fuel tanks are what to check first.
The Jefferson 42 Sundeck is a Taiwan-built sundeck motor yacht sold from 1986 to 1995. The PowerBoat Guide lists her at 41'8" overall with a 14'3" beam and a 3'7" draft, and says a radar arch and hardtop came standard. No source publishes her air draft, so it has to be measured. She carries 350 gallons of fuel per the guide, and 250 to 260 hp diesels cruise at 12 to 14 knots. Owners describe leaks at the windows and deck fittings as the model's weak spot.
How to read the tags on this page.
PATTERNtwo independent sources agree; confirm it on the boat you're looking at
CLAIMstated by one source, not yet confirmed
QUESTIONopen, and settled by looking at the boat itself
Sources are linked where published.
Reading the boat
QUESTION
Is this the 42 Sundeck, or the 42 Viscount or 43 Marlago that followed it?
The PowerBoat Guide dates the 42 Sundeck to 1986 through 1995. Jefferson also sold a 42 Viscount from 1990 to 1994 and a 43 Marlago Sundeck from 1990 to 1997, and brokers label all three loosely, so a 1990s "Jefferson 42" could be any of them. Listings for those later boats show different beams, tanks and engines, so this page's numbers may not fit them.
src:
PowerBoat Guide (HMY), Jefferson 42 Sundeck, 42 Viscount and 43 Marlago Sundeck pages
Your move: Read the model and year off the hull identification number, and compare the beam and tank sizes with the ones on this page.
Air draft
QUESTION
No published air draft, and a radar arch and hardtop were standard
The PowerBoat Guide lists her clearance as not available, and we found no owner measurement we could open. The guide says a radar arch and a hardtop came standard, and at least one owner's boat has no arch, so two 42s can stand at different heights. Against the Loop's 19'6" limit this is the number to get before anything else.
src:
PowerBoat Guide (HMY), Jefferson 42 Sundeck (1986 to 1995)
Your move: Measure from the waterline to the top of the arch with the antennas up, and again with the arch down if it folds.
Draft
CLAIM
About 3 feet 7 inches of draft
The PowerBoat Guide lists 3'7" of draft on a long keel. That works for the Loop's shallow stretches, with less room to spare than a 3-foot boat in the shallowest anchorages.
src:
PowerBoat Guide (HMY), Jefferson 42 Sundeck (1986 to 1995)
Your move: Confirm the loaded draft with the seller, since fuel, water and gear add to it.
Fuel & range
CLAIM
One listing says 6 gallons an hour at 8 knots, without saying whether that's both engines
A 1989 boat's listing says she cruises at 8 knots burning 6 gallons an hour on twin Cat 3208s. The PowerBoat Guide lists 350 gallons of fuel. Holding back 10% leaves 315 gallons. If 6 gallons is both engines together, that's about 480 miles at 8 knots, plenty for the 250 miles from Alton to Paducah. If it's 6 gallons for each engine, the range drops to about 240 miles, just short of that leg. The guide's own figure is a 12 to 14 knot cruise with 250 to 260 hp diesels, with no burn given.
src:
American Yachts listing, 1989 Jefferson 42 Sundeck (seller's words); PowerBoat Guide (HMY)
Your move: Ask for a fuel-flow reading for both engines together at 7 to 8 knots on the sea trial.
CLAIM
The original fuel tanks are black iron and sit behind the engine-room insulation
A buyer looking at a 1987 42 on Trawler Forum read the tank nameplates: two 210-gallon tanks of 3 mm black iron. The buyer could only see the tops through a gap in the insulation, and one had heavy rust curling up. Another poster, writing about a Jefferson 42 of the same vintage that their father owned, listed failed welds in a fuel tank. Owners on that thread put a yard replacement at $10,000 to $20,000. Two 210-gallon tanks also make 420 gallons, not the 350 the guide lists, so some boats may carry more fuel than published.
src:
Trawler Forum, "Jefferson 42 Black Iron Fuel Tanks" (Dec 2019); Boat Design Net, ClarkT (2012)
Your move: Ask whether the tanks have been replaced. If not, have the surveyor look at the tops and seams with a borescope, and price replacement into the offer.
Leaks
PATTERN
Owners say leaks are the model's weak spot: windows, deck fittings and the sundeck doors
Owners of 1987 and 1989 42s on Trawler Forum describe the same problem on their own boats. The trouble spots they name are the aft stateroom window, the two windows above the dinette and galley, the deck rails over the forward head, and the base of the sundeck doors, where water ran down inside the walls of the master stateroom. One owner called leaks the Achilles heel of the Jefferson. A 1989 boat's survey, posted on the same thread, noted water stains around the windows, hatches and ports. On Boat Design Net, a poster listed improperly bedded fittings on a 42 their father owned.
src:
Trawler Forum, "Jefferson 42" thread (2019 to 2020, several owners); Boat Design Net (2012)
Your move: Look behind the paneling at the window corners in the aft stateroom and galley for stains and lifting veneer, and have the surveyor run a moisture meter around every window and door.
Hull & structure
QUESTION
Is the deck and sundeck core dry?
The PowerBoat Guide describes solid fiberglass construction. A poster on Boat Design Net said a Jefferson 42 of the same vintage that their father owned had rotten balsa core in the hull sides, swim platform, sundeck and deck. That's one secondhand account against the guide, so treat it as a place to look.
src:
Boat Design Net, ClarkT, Mar 28 2012; PowerBoat Guide (HMY)
Your move: Ask the surveyor to sound and moisture-test the decks, the sundeck and the hull sides above the waterline, with a core sample if the readings are high.
From owners
CLAIM
A former owner's repair list, at about 4,400 hours
A former owner of a 1986 42 Sundeck sent in this list of what failed and what was done: window leaks were repaired, the holding tank was replaced, all three air conditioners were replaced, the vacuum-flush toilets got new seals and joker valves, and the waste lines, damper plate, starboard transmission, props and electronics were dealt with too. Reported at about 4,400 engine hours.
src:
Owner report: a former owner of a 1986 Jefferson 42 Sundeck (Oct 2026)
Engines
The engines research is part of the full profile inside the
product. It covers factory options, tested performance and the engine-specific
questions in our members' dossiers, and it travels with every dossier and survey brief
built on this model.