Overheated 1989 4.3 OMC questions...

[maine4winns]

Well, I am happy to report that our sea trial went well yesterday after replacing the entire water pump assembly and hose, replacing the thermostat, verifying no clogs from an older chewed up impeller (fun taking power sterring hoses off! LOL), removing batwing exhaust manifolds to ensure they were not overly corroded (checked engine water ports as well) and lastly preplacing the destroyed exhaust flapper valves!

Sat at dock until it got to the temp for the thermostat to open and prayed to the boat gods... Yup - she jumped back to normal operating temp. I hope this post helps others, although there is a lot of info on overheating I/O's - I think this post has it all in one! LOL

Thank you all, especially Lou C. You are a legend!

 

[Lou C]

That looks great including the fish! Every 3 seasons or so I’d change the impeller & every 5 seasons remove the manifolds & rod out those 4 outlets. Doing that I doubt you’ll have a problem. Just watch for any water in the cyls. I never had that problem with the OMC batwings but in salt water the longest I used them was about 6 seasons. The idea is always replace before failure; because getting water in an cyl causes lots of damage. I never had that issue replacing them on time.
Operating temps should be 160-175. Manifolds will be about 90-100* at idle & hit a max of about 140* after running on plane.