4.3 to 5.7 mercruiser swap

[lakeshore2016]

I have a 94 JC 266 tritoon with 4.3/alpha one setup.

How much trouble to swap to a V8 5.7?

I'd assume motor mounts. Would the 5.7 mate up to existing alpha one?

I have read may have to take it easy on the alpha one. But I see these 266's for sale with 350/alpha one setups, I'm pretty sure. Is there a way to tell the gearing in my alpha one?

[rbtnt]

If you can see the gears by taking a cap or cover off, you can you this chart.

http://www.mtboats.com/mercuryoutdrivea ... atios.html

[Bamaman]

Forget it. It is doubtful your engine pod is large enough to handle such a large engine. Postponement IO's need to be done by the factory. It is easy to get them out of balance.

[Bryden24shp]

I did this swap before in a 85 Forrester Cuddy. Motor mounts will need relocated, the Alpha One will handle up to 300 HP, if not beaten on to bad. Sea Ray used the Alpha's in the old Pachanga's with 260 HP 350's and 300 HP 454's. Chris Craft and Mach 1 did the same. If I remember right, I had to push the mounts forward about 4 to 5 inches. Like Bama said, the hard part was making sure the coupler and input shaft line up correctly with the lower unit. I was in luck because I had access to a line up shaft that my brother got from his father in law, who ran a Merc repair shop. Used exhaust manifolds will be easy to find. But also like Bama said, make sure you have plenty of room before you dig into it. Fun swap if it works out for ya!