5.0L 305 OMC rebuild

[George5th]

I just acquired a 1988 Bayliner Trophy with a 5.0L 305 motor and OMC Cobra outdrive. It hasn't run in years. If an engine rebuild is required and we follow Youtube advice and change heads/intake, etc... and increase the horsepower from 230 hp to 360 hp, does that affect the out drive? If so, what modifications would need to be made?

 

[PITBoat]

There'll be plenty of advice forthcoming about don't put money in something with an OMC due to obsolescence, etc., but unless there's something about the motor that precludes it, I'd personally just try to see if it can be made to run inexpensively like it is. Forget the high HP stuff for now. You might find other problems with the boat, drive, whatnot like that, that'd ruin everything after investing time and $ in the motor only. Like a guy who does a bunch of detailed interior, etc. work, only to find out that, Hey the thing leaks, etc. when he gets it out on the water.

 

[Lou C]

The standard OMC Cobra is good to about 300 hp, a rebuilt marine 305 is not going to put out anywhere near that, keep in mind you can't go radical on the cam on a marine motor because of exhaust reversion, even if rebuilt with Vortec heads, a 4bbl intake and carb, you are talking like maybe 250 hp. If the Cobra drive is in good shape it can last a long time as long as the shift system is maintained.

 

[Scott Danforth]

I just acquired a 1988 Bayliner Trophy with a 5.0L 305 motor and OMC Cobra outdrive. It hasn't run in years. If an engine rebuild is required and we follow Youtube advice and change heads/intake, etc... and increase the horsepower from 230 hp to 360 hp, does that affect the out drive? If so, what modifications would need to be made?

There is no way to get a 305 to put out 360hp and live in a boat

You need more cubic inches. A stroked 350 (377 or 383) would be my first suggestion

 

[alldodge]

Youtube same as forum can be a dangerous place to look for advice. At least forums have other poinions to advise if you get info that another thinks is incorrect. There are some good ones and some not so good. Don't see you being able to get a 5.0 to produce 360hp.

Would be better to replace it with a late model 5.7 vortec. The drive should have no problems handling the higher hp