1977 42 Flybridge MY w/Gas Engines

Everyone here will tell you to get a survey, a GOOD survey before anything.

My friend used to look at boats with me prior to purchase and he would ask me if I wanted him to tell me what I wanted to hear or tell me the TRUTH. Meaning, don't fall in love with the boat until survey is complete.

I always felt 40 feet was the cut off for gassers.
Also, Bert's are harder to keep on top than a flatter bottomed sport fish, another reason for diesels.
Lastly, 1000 hours was about when you would do the top end rebuild of a gas engine.
Do you know if there has ever been any work done on the engines ?

Personally I wouldn't want a boat of that size and weight powered by gas engines. That engine doesnt make peak power until 5k rpm, one thing to remember is that it's always running up hill. Big blocks don't like to rev and they are thirsty, as Chesapeake said be prepared to rebuild the top end. There are so many 42's for sale I would look for one with detroits

Bertram. Deep V. Semi-Planing. Top speed when new 22 knots, cruise 14. Draft 4'0". It's in the Bertram forum section, hence my guess. Maybe a little faster with the larger engines it has.

And to quote from a write up on the boat.

With her proven deep-V hull, the Bertram 42 can handle sea conditions that keep other motor yachts her size in port. Several engine options were offered over the years. Standard 330hp gas engines—a poor choice in a heavy 42-foot motor yacht—will cruise at 14 knots and reach 22–23 knots top. Twin 335hp Detroit 6-71 diesels deliver a 16-knot cruising speed (18–19 knots top), and optional 435hp 6V71 diesels cruise around 20 knots.
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Same hull as the Bertram 42 Convertible.

Efficient power package, No. Diesels would be a lot more efficient in terms of fuel consumption. Should cruise faster than the published 14 knots with the 502's. I would guess about 16-18 knots. 502's are near the end of their life expectancy at 1200 hours usually. Pushing that boat with gas inboards is A LOT to ask out of them. Some people do get 3000 hours out of them, but running at cruise in a 42' Bertram MY puts one heck of a stress on them. The previous owner might have run at hull speed most of the time though.

there is the other side to consider with a gas powered boat of this side.

If only using the boat under 100 hours a year and happy with 7 knots, the gas boat will be cheaper to maintain and service in the long run.


I bet you could drop in a long block replacement BBC for around $3k.

I do agree that a 42' boat is the upper limits for sure on gasoline power.

a short season, limited hours, northern lake boat with this power could make sense.

Compared to 6-71's I don't think so. Add up the price of a set of exhaust manifolds and risers every 5 years, plugs, wires, cap, rotor, coils, fuel pumps, etc etc.....Replacing or rebuilding the gas motors every 1000-1500 hours, I'll take the 6-71's and their cheaper fuel and much lower fuel consumption anyday in a boat like this. A set of 6-71's will usually go almost 10,000 hours.....

I would imagine with the OP located in Michigan, there are a considerable number of gas boats in the area. My first five boats were all on an inland lake and all gas like every other boat around them. However, in this particular boat, there was only one reason it was gas and that was initial cost. In the initial price today the difference would be $40-50,000. I'm sure it was significant when that boat was built. Of course the difference remains significant at resale too, so don't think it's a great deal because it's less expensive than comparable with diesel. It should be less.

Years ago I looked at a 42 Post with gas engines. I thought the engine compartment was a dream come true. You could put a bunk on the outboard side of each engine ! Fortunately I had a mentor that set me straight on the fine art of internal combustion engines and their possible limitations.