Engine Swap 350 to 383 Questions?

[ttop87gn]

Hi i have a 1988 Cobia runabout 19'7" with a 350 mercruiser alpha 1. I'm looking for more power and thinking of replacing it with a 383. I'm a good mechanic especally chevy small blocks, but I don't know much about boats. My questions are<br /><br />1. the 383 is a 2 piece seal im sure the boat motor isn't how does the flywheel couple to the drive (can't find any info, pics, etc in the repair manual I have) what issues will i have here. I know I need a 400 flywheel but beyond that im lost.<br /><br />2. This engine (actually one i've kept for a spare for my drag car) will make over 400 HP even with a small cam in it. Will the alpha 1 handle this power level? Is there anything I should change in it for this engine, or am I just asking for it trying to run this engine?<br /><br />Thanks for your replys I look forward to reading them. If I do this it will be a winter project, trying to get all the info I can before I start, my main concern is whether or not it can handle the power or not. If it won't I would rather live with it the way it is until I can afford a different boat.

 

[DJ]

Re: Engine Swap 350 to 383 Questions?

I can't answer your engine questions. However, if you have an Alpha drive, it won't hold 400 horses. At least not very long.

 

[John Carpenter]

Re: Engine Swap 350 to 383 Questions?

I agree regarding the Alpha drive...it's not going to hold 400 hp. They are rated I think for 300 hp., and you can probably get that out of a 350<br /><br />There is a lot of difference in how a marine engine should be set up versus a race car engine. The power requirements are vastly different. For more than you want to know about this, get a copy of a book by Dennis Moore. I believe it is called "Small Block Chevy Marine Performance". I would know for sure if my copy wasn't loaned out It may be available here from Iboats...if not, go to Amazon.com

 

[Bondo]

Re: Engine Swap 350 to 383 Questions?

1. the 383 is a 2 piece seal im sure the boat motor isn't how does the flywheel couple to the drive (can't find any info, pics, etc in the repair manual I have) what issues will i have here. I know I need a 400 flywheel but beyond that im lost.

You'll need the Coupler that bolts to the Flywheel,(I Believe this is the Same bolt pattern as an 11" Clutch/pressure plate)<br />Not the coupler that bolts to the Crankshaft.......<br />

2. This engine (actually one i've kept for a spare for my drag car) will make over 400 HP even with a small cam in it. Will the alpha 1 handle this power level? Is there anything I should change in it for this engine, or am I just asking for it trying to run this engine?

Ayuh,<br />You're going to have Problems.................<br />The Alpha's are Good to about 300hp.......<br />IF you're Very Gentle , It'll last awhile........<br /><br />The Only proformance Up-grade for the Alpha,<br />Is to Up-grade to a Bravo..$$$$........