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My buddy is in the process of repowering a 1970 31. He is dropping gas motors back in just because diesel is crazy expensive right now and he got a deal on some used motors. He still has the original tank in it and I am urging him to pull it out because of possible ethanol issues. If he gets a new aluminum tank built, how big can he go and still fit in there? We havent done any measuring yet. Thanks!

A lot has to do with the year of the boat. The early ones had 165 gallon tanks. later ones kept getting bigger by virtue if raising the decks. Walter

I have a 69 FBC and I think I'll get about 240 gallons--I haven't pulled the old tank yet. The 240 is baed on measurements with the tank in.

I have a '72 with 231 gallons marked on the tank. This was the first yr of the larger tank. Prior yrs had 165.

Defintely have him pull tank.

I had the 165 and went with a 220 Alum tank. I could have went larger by adding more to the rear of the tank, but in hindsite I should have made a bit smaller. The extra weight in the back makes the boat a pig, unless the tank is full, empty or I run harder.

Thanks alot guys!

make damm sure he doesnt run those engines with the old tank. i learned the hard way. i ended up with 241 gallons with the new tank

I put in a new stainless tank the same size as the old fibreglass one but 2" longer in my 31 express and it topped off at 233 gal. When your having yours made, put in returns and extra fills for deisel, in case you will change. Also for a generator.

I have a 70 bahia mar and went with a LLC Bertram 31 fiberglass tank. It's a little taller and goes all of the way back to the rear bulkhead. 260 total gals. Seems like a gas boat could do the same, if not a little better, with alumimun or stainless.