3.0L omc cyl head Question

[Jerry San Diego]

I have a 3.0L OMC 1989 140 hp 181CID. I have had to replace the cylinder head due to a hole in the #4 cyl which allowed water to get in the head. . I could not find a new head with the same casting # as the old one. I bought a used head and took it to a machine shop had it checked and installed it. Engine seems to run good now. Question is: The new head is different from the old one in that the intake exhaust ports are smaller than the new head. The Old head had much larger ports and were the same size as the manifold intake and exhaust ports. The new head has smaller ports, much smaller than the intake exhaust ports on the manifold. I used the gasket for the larger ports. The boat shop I purchased the head from states the smaller port head will operate well with the larger port maniflod and will not cause any problems. He stated the new head with the smaller ports is a better head. My question is : Does anyone know if this mismatch will cause me any problems.<br />Thanks<br />Jerry

 

[rodbolt]

Re: 3.0L omc cyl head Question

hello<br />most likly not. I have seen it mis matched from the factory. I think there are 3 or 4 port congigurations of the3.0 head/manifold. if it runs wellnow ,run it. as long as it still accelerates smoothly and the WOT rpm is still correct.

 

[Silvertip]

Re: 3.0L omc cyl head Question

There may be a slight drop in top end performance simply due to the head design but overall, there should not be a problem. In fact, you may even notice a little better bottom end power. Mating a manifold with smaller ports than the ports in the head can be a problem.

 

[Jerry San Diego]

Re: 3.0L omc cyl head Question

Thank you Rod Bolt and Upinsmoke for you responses. I appreciate your responses. I feel better now about the head- Will just run it and see how it goes-- Thaks so much.<br />Jerry

 

[Jerry San Diego]

Re: 3.0L omc cyl head Question

Just an up date here. I have taken the boat out a couple of time and put about 6 hrs. on it catching lobsters with my hoop nets. It runs great and purrs like a kiten. Doesn't seem to be any change in RPM from the original head. It appears the mismatch isn't causing any problem at all. <br />Thanks again for the help.<br />Jerry