Changing OMC 5.7

[foresteronw]

I have a 1989 Sunbird Eurosport with an OMC 5.7L. I have been thinking about putting a new motor in it and I am wondering if this is something that is fairly easy to do. I am an aircraft mechanic and have a really good mechanical ability. I have the manual and it seems that it wouldn't be that hard but I am not sure if there is something that I am missing. Also is there anyone that knows how many horsepower this engine would have. 1989 OMC 5.7L 4bbl carb.

 

[Bondo]

Re: Changing OMC 5.7

It's about 250, 260hp...<br />It's Much easier to pull a boat motor than ANY auto motor......<br />If you're an A&P mechanic, it'll be a walk in the park.....<br />Pop it out, punch it .030 over, add a 3.75" long stroke crank, 383cid, 400hp will be easy....

 

[Mufasa]

Re: Changing OMC 5.7

I agree. Don't replace the motor. Pull it out and freshen it up. Then all the fasteners and mounts for the stringers will be positioned correctly. Miss-alignment causes a lot of trouble with failed coupler assemblies. Also a lot of the componants are marine specific for spark and burn tests.

 

[charleswmoore]

Re: Changing OMC 5.7

I did the 383 thing about ten years ago and it gives you massive bottom end. Don't forget you have to do some grinding to make room for the extra stroke. Well worth the effort and very reliable method to gain some extra ponies without going crazy on high peformance. Also I think I had to retain the flywheel and harmonic balancer?<br />Don't remember the details but I do remember that if you want it to idle and run smooth let the machine shop balance the motor also.

 

[Boatin Bob]

Re: Changing OMC 5.7

Something to consider if you beef up the HP is whether the drive can handle it. OMC used the King Cobra for the big blocks which was a bigger beefier drive.