I just bought a 21' boat powered by 1987 OMC 350 and Cobra outdrive. I was told both were fresh rebuilds, but yet to confirm this. I have a stock 2000 EFI 5.7 Mercruiser and Alpha 1 outdrive (fresh rebuilts on stands). My question would be is Does it benefit me to do the change out or do I just run the OMC and tweak it out. I am fairly new to powerboats, but have been told by a few week-end warriors to go ahead and swap them out to gain performance and for future performance upgrades. Any help would be appreciated

OMC's made great anchors but you can no longer buy them because they went bankrupt.

That statement is not totally true.OMC quit the seterdrives back in 93 or 94 when they made some sort of a deal with Volvo.When they went under the sterndrives were no longer in production.
Now Bombardier has purchased OMC and I have herd rumors of a new OMC sterndrive comming soon.

However Cobra is not the best drive but it not the worst either,they make plenty of parts in the "Aftermarket" to keep your boat running.

Mike
Go with the Merc package, the OMC is not as dependable.
If you are running a small block in front of it it MAY LAST
But if your running a big block in front of it the lower unit just dies without even hammering on it.
Good luck
Brian

beat the bag out of the OMC for a year or 2, then swap.

He already established thagt he is running a smallblock carb motor.

I see no reason to do a swap till there is a failure severe enough to warrant it.

I would run it what the hell,if it has been freshened up and you maintain it you'll probably get good service out of it,providing it was done right.

If you dump the OMC I could use some of the gears out of the lower..

If you dump the OMC I could use some of the gears out of the lower..

OMC didn't stop making SternDrives because there was too much demand for their product. They had their shot and they went under.

You have two drive packages for a 21 foot boat. You don't need both. If you are pinching pennies then by all means sell the Merc (You'll get more money for it) and try to run the OMC and just deal with the likely headaches that so many boaters ran into that gave OMC their well deserved reputation for being junk.

On the other hand, if you can afford it and like worry-free boating then put the reliable MERC power in and try to sell the OMC.

There's no question about which powerplant is better - it all comes down to a question of which you can afford.