1985 OMC 3.8l Max safe RPM operating range

[Canadian thundercraft]

Just installed a 3.8l that was purchased from a running boat. It appears the engine was rebuilt recently but i am not sure if the engine was rebuilt from a GM 229 automotive based engine. I am not 100% sure that the cam was changed to a marine cam. What would the operational difference be between the 2 camshafts. I am currently getting just over 4000 RPM at WOT (19' 1985 Thundercraft 15x7 prop I think) and about 35 MPH with nose up full trim. The last 1/3 or 500 RPM of the throttle only seems to make more noise than anything. What is the max safe RPM of this engine? THX in Advance

 

[Howard Sterndrive]

Re: 1985 OMC 3.8l Max safe RPM operating range

4600 rpm is max.

I don't know how you would check the cam, but I suspect it's a marine one in there... you might not even get the boat on plane with the smog era car cam (110HP auto vs. 170/185HP marine).
Otherwise the engines are identical so I would use a car engine if I was looking for a rebuildable core.
If you have doubts about the build, there is one thing I would check in relation to power and that is the timing of the distributor to #1 TDC on the proper distributor lobe. That 229 is a weirdo like no other Chevy V6 or V8 as far as that step goes. Here's the trick that many do not know about and you have a 50/50 shot without knowing- and of course the OMC manual says nothing about it:
http://marinemechanic.com/site/page105.html

Mercruiser used the same motor and distributor and explain it in their manual.

 

[Canadian thundercraft]

Re: 1985 OMC 3.8l Max safe RPM operating range

Thank you for your reply. We will check TDC to be sure they got it right.