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87 5.7 Omc exhaust over heat

I

Inthebilgeagain

New member
Looking for some help here with an overheat. Marine mechanic who is stumped. My 1987 3255 Avanti. Port motor runs at 150-160, risers are at 200 degrees at 3000 Rpm where stbd riser is at 110 degrees. Eventually when running it will stumble run like crap and shut down, acts almost like a hydro lock when trying to start up, I believe distributor is heating up. I have replaced impeller, circ pump, copper tube in drive, thermostat/ housing, risers and manifolds, compression test, block pressure test. I have also put clear hose on intake before thermostat housing (have solid water flow) clear hose from therm housing to exhaust is air raided with decent flow. I’m looking for any opinion’s other then ditching the OMC’s because I can’t afford a repower right now. Thanks!🚤💦
 
Inthebilgeagain said:
Looking for some help here with an overheat. Marine mechanic who is stumped. My 1987 3255 Avanti. Port motor runs at 150-160, risers are at 200 degrees at 3000 Rpm where stbd riser is at 110 degrees. Eventually when running it will stumble run like crap and shut down, acts almost like a hydro lock when trying to start up, I believe distributor is heating up. I have replaced impeller, circ pump, copper tube in drive, thermostat/ housing, risers and manifolds, compression test, block pressure test. I have also put clear hose on intake before thermostat housing (have solid water flow) clear hose from therm housing to exhaust is air raided with decent flow. I’m looking for any opinion’s other then ditching the OMC’s because I can’t afford a repower right now. Thanks!
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check timing... if the distributor is over heating, the module could have failed and causing a firestorm in there creating timing issues, which wcan cause the cylinders to overheat...
the cooling system is obviously doing its job, as the engine isnt over heating, but that doesnt mean the pistons cant get so hot they wont melt down or cook the exhaust valves.
did the mechanic check for obstructed exhaust? that is another thing that will cause the problem.
 
Timing is at 8 degrees, good point,thinking I’m going to try new module or distributor because I believe it’s getting too hot. Yes I had drive split, no dropped or missing flappers. I replaced riser & manifolds and made no difference.
 
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