1988 4.3 OMC overheated and melted paint

[theundercut]

I have been trying to get a 1988 4.3 OMC Four Winns with Cobra Outdrive going. I replaced the bat wing manifolds with 2 piece set up as described by Lou C in previous posts. I performed the upgrade but then overheated almost immediately once on the water, melting the paint on the new elbows. I was only out for about 10 mins and immediately shut it down. I have since replaced the thermostat, put the therm housing in a evaporust bath, placed in a ultrasonic bath and cleared all the passageways. See photos. I have run a boroscope through the exhaust checking for blockages. Checked the impeller, which looks brand new but I am going to replace. I am running out of ideas as to why this is overheating. Any assistance would be greatly appreciated. Photos to show whats been done. Thanks!

 

[Lou C]

That 90* down pipe is FRIED! When I had my overheat I thought it was bad but it didn’t even burn the paint on the old OMC manifolds & alu exhaust pipes. The impeller looks ok. What brand of manifolds & elbows did you use?
What I’d do is put the boat in the water and bring a helper with you. Disconnect the raw water intake hose and hold it up. Have your helper start the engine (just enough to see how much water flows from that hose, like 30 sec). You should see a stream of water 2-4” high. If not your raw water flow is way too low. I would then check the P/S cooler for old impeller bits & remove the drive & split the upper & lower to check the water tube grommets. If those don’t seal right you will have low raw water flow. BTW bad overheat will melt these grommets. Did your flappers melt & block the exhaust?

 

[theundercut]

I got this Barr Kit. I did disconnect the raw water intake off the thermostat housing after the overheat, after waiting 1 hr., as we had another boat with us and they took the kids for spins around the pond and used my boat as the swim platform anchored just off the shore. It definitely did not go up 2-4" high. The photos are from a boroscope showing the inside of the exhaust from the top down to the Y split and then from the exhaust bellows up to the Y. I could not see any remenants of the flapper, I suspect it was removed previously. I think at this point my next step is removing the drive and taking it from there, I can't find much literature on the water tube grommets. I am still waiting on the SELOC to arrive. Where is the P/S cooler? I have not seen anything resembling a P/S cooler.

Thank you so much for you assistance! Trial by fire here and doing my best to research and figure it out before asking here.

 

[Lou C]

Does yours definitely have power steering? If so the cooler is behind the engine. Follow the raw water intake hose back….

 

[theundercut]

remove the drive & split the upper & lower to check the water tube grommets. If those don’t seal right you will have low raw water flow. BTW bad overheat will melt these grommets. Did your flappers melt & block the exhaust?

Is there supposed to be a grommet in pic 7 w/ the exhaust bellows? The copper tube running through the stern?

Does yours definitely have power steering? If so the cooler is behind the engine. Follow the raw water intake hose back….

Ill have to take a closer look, I am not certain. Ill get back after, after work tonight.

 

[Scott Danforth]

I am still waiting on the SELOC to arrive.

Seloc manuals are mostly wrong information

Get a factory manual

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