330 to 260 swap....1981 310 sedan bridge

Jeff8330

Member
Apr 22, 2019
31
Toms river, nj
Boat Info
1981 srv 310 sedan bridge
Twin 454 mercruisers
Engines
T/340(454) mercruiser straight drives
Hello all, I have a 1981 310 sedan Bridge. She's a great boat. Haven't had her long, but the more I tear into this boat, the more I love it, and the build quality.
Anyway, she's powered by twin 330 (454) mercs. Mated to B&W velvet drives. The motors are very tired, probably will need rebuilds soon. I'm looking at my options. I have access to a pair of early 80s 260 mercs. I know these are just gm small blocks, and I can get them for almost nothing from a very good friend who will have to dump them soon anyway due to storage issues. They are low hour rebuilds that were just pulled out of the boat that had rot issues. This boat isn't THAT heavy, and I know two small blocks would pull it out of the water nicely. My transmissions are fine, bullet proof as we all know. What would I need to do to have a set of small blocks bolt up to my current transmissions? Bellhousing issues?? I'm new to the world of inboards and am currently learning the differences in transmission setups. However, not new to marine engines. What am I looking at here? I'm assuming it would be almost a direct swap. My 87 Chris craft COMMANDER 333 had two merc 270s in it. That boat was so much better on fuel and it was more than enough power for me. It was just as heavy as this boat, and very comparable as far as size and vintage. Anyway, thanks in advance...... Wheels in my head are turning so you might get alot of questions if I proceed.
 

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