Is is possible- 4.3 to 5.7 engine swap?

[emmettfire45]

Hello all I have a 1987 Sea Ray Seville MC with a 4.3 Merruiser and Alpha Out drive. Would it be possible, feasable and economical to switch to the 5.7. I could do alot of the work myself and I am wondering what I might expect with speed increases, gph decreases, and difficculty. Also Could I keep the alpha out drive as Im not planning on building the motor up? Also what about thru hull exhaust? Thanks for the help ahead of time.

Aaron

 

[MaddyDean]

not sure is you can do it but here is a link to Merc's site

http://northamerica.mercurymarine.com/engines/inboards/sterndrives/alphaone.php

 

[tdappleman]

Are you simply looking for more power or is the 4.3 in need of replacement? What intake manifold and carb do you have on there? The 4.3 is essentially a 5.7 minus 2 cylinders so theoretically it could be done assuming you have enough room in the engine compartment. As far as the Alpha holding up is another thing entirely and I don't know the answer to that one.

 

[Southpaw II]

Expect (plan for the worst) to change the Alpha to get the right gear ratio and also the prop. If you are dead set to do this, find a salvage boat and rob the drivetrain from it.

 

[Nehalennia]

The Alpha drive will hold up. Many 5.7s are paired with Alphas. Yes, it can work but you will need to look into the proper gear ratio for the 5.7 v. the 4.3. That one I'm not sure of.

 

[emmettfire45]

Excellent thank you so much for the posts. Im not 100% on the Idea but I am going to check it out more. I am seriously looking into it though. Thanks for all the help I will work on it.

 

[Creekwood]

You may be better off just finding another boat with a low hours 5.7 and sell yours. The cost to upgrade would probably not be worth it. Try estimating the selling price of your boat now, add the estimated cost to upgrade to a 5.7 motor/drive. Take that total dollar amount and research what kind of replacement boat you could get. You might change your mind.