Re: going from a 4.3 to a 5.7 350
Actually a 4.3 V6 is a SBC V8 with cylinders #3 and #4 removed. (Or is it #5 and #6?) Anyway, the missing cylinders come from the middle of the block, not the front two. The reason to make that distinction is that it means the from motor mounts in the boat will be off by approximately 4.4 inches. It can also make the exhaust hard to line up.
Wakeboarder, my dad did this swap in a 19' Sea Ray Seville. I can give you all the specifics you want in a PM. But here's what I typed to another guy a week ago:
****"Doable, and not a pain in the butt, if you buy a complete Mercruiser 5.7, and have mechanical ability. My father did it on an 89 Sea Ray he owned. The "only" issues he had were that the fuel tank was in the way of one of the front of the engine accessories, and the exhaust hoses were a little hard to get to stay on the Y-Pipe. Moving the engine mounts was easy, since his were just lag screwed into the stringer and there was sufficient stringer ahead of his existing ones to move them the approxiamtely 4.4 inches it will take. He did not have to re-gear his outdrive, but it did take a 25 pitch prop, which are not common.
Big pain in the butt if you try to piece it all together, one part at a time."****
I typed this back in July to a guy who wanted to install a 5.7 in place of a 4.3 in the same boat as what my dad did:
#####"Moving the motor mounts is easy. The "block" where they are currently screwed in, should be long enough to allow you to unscrew them, and rescrew them where you need them.
You fuel tank will probably be in the way. At least my dad's was, when he put the 5.7 in his 19' Seville. He eventually bought a new fuel tank to allow the clearance for the front of the engine accessories. it cost real money, though.
Your engine cover will probably hit the water pump pulley, so get ready to move it a little.
My dad made the V6 Y-Pipe work, but did have some issues with hose fitment. Can't remember why exactly, though.
He had a 1.81 ratio drive, and he was able to reuse it, just with a 25p prop. Now his 5.7 that he installed was no modern Vortec motor. It was a 1987 5.7, that with the cam and carb he used, probably was close to 225hp. If you install a Vortec engine that's making a lot of HP, you should probably change the outsrive. For $1195, you can get a complete Alpha One replacement from SEI. So I would not mess around with paying someone to change gear sets.
Your best course is to find a complete take out 5.7 off e-bay or somewhere. Yeah I know they are $$$, but you are going to have to buy all exhaust the stuff to fit a 5.7, and the intake, so you may spend $$$ buying it piece meal any way." ####
