Complete drive swap

[Short Stroke]

Hi all. I have a 1989 Four winns 200 horizon. I'm getting ready to start rebuilding her. She has an OMC 5.7 COBRA 260hp with a cracked block. I have another block to build. Here is my question.... I also have a 1989 sea sprite with a Mercruiser 5.0L 230hp with alpha one sterndrive. (See older post). This engine is possibly (most likely) locked up. What are your opinions on swapping out the OMC for the Mercruiser? And why?

 

[achris]

You can still get parts and support for the MerCruiser, but not the Cobra.

 

[Short Stroke]

That's the direction I'm leaning toward. I've always heard there were less problems with the Merc, and I have pretty much everything I need from the donor boat. I figured I would try to sell the OMC stuff.

 

[Bondo]

Ayuh,..... Welcome Aboard,..... Sounds like a solid plan,.....

 

[matt167]

I wouldn't 'build' a SBC.. Under $2k buys a new GM long block last I knew and I'm not sure you can build for less than that. Swap a marine cam and the Mercruiser specific stuff and drop it in.. Forgot marine gaskets and marine core plugs

 

[Short Stroke]

Building them is the fun part. And I can build it well over 300hp for $2k, lol.

 

[matt167]

Building them is the fun part. And I can build it well over 300hp for $2k, lol.

Sure, you could build a 383 stroker, run about 350hp, but then your going to twist up an Alpha if your not careful. Being a marine engine, you can only do so much due to camshaft limitations due to exhaust reversion

 

[achris]

Building them is the fun part. And I can build it well over 300hp for $2k, lol.

If you're running an Alpha drive, keep it at 300hp... Yes you can build a marine 383 to make 450hp, but you won't have a drive for long (or update to a bravo)...

Interestingly, I'm about to start building a couple of 383s to replace a friend's aging 260s. The gearboxes (they're inboards) are 71C's and are about as strong as an Alpha, so I have to keep the power down. Not easy on a 383. About the best option is going to be around 320hp. The great thing is that at such a 'low' power (for a 383) the torque curve is monster! His normal operations are cruising around at about 22 knots. Those engines will be in picnic land! And that's the thing about marine engines and 'power'... Very very few people use a boat engine at max revs making max power. What you really want is max TORQUE and as low as you can make it. If you can build a 383 that makes max power at around 4600rpm and max torque at around 2800rpm, you just built the best boat engine you could! It'll last forever, and it'll be great on fuel... (and at a buck 65 a litre , that's a good thing!)

 

[Short Stroke]

You all are right, I know the alpha 1 was rated for only 300hp and under, I was just being onery . I have a good 350 crate motor long block with extremely low time and miles on it. Both of the other two engines have very low hours on them. I'm planning to reuse all parts possible so basically I'm gonna be doing a minor overhaul with marine gaskets and new rings and bearings. I'm not interested in spending more than I absolutely have to, unless it's necessary..
I have to pull the omc 350 regardless, so I figured it would be the best time to do a complete swap to the Mercruiser.

I'm just trying to decide if it's the right thing to do.

Thank you all for your input and opinions.

 

[Scott06]

You all are right, I know the alpha 1 was rated for only 300hp and under, I was just being onery . I have a good 350 crate motor long block with extremely low time and miles on it. Both of the other two engines have very low hours on them. I'm planning to reuse all parts possible so basically I'm gonna be doing a minor overhaul with marine gaskets and new rings and bearings. I'm not interested in spending more than I absolutely have to, unless it's necessary..
I have to pull the omc 350 regardless, so I figured it would be the best time to do a complete swap to the Mercruiser.

I'm just trying to decide if it's the right thing to do.

Thank you all for your input and opinions.

If using an of the shelf crate motor not originally intended for marine applications - just make sure you verify the cam will work in a marine application. Generally truck cams are ok but if it is a muscle car crate engine you will need a cam swap.

Just on parts availability alone the merc swap makes sense.