1980 Evinrude 150 hot at WOT

[Striper68]

Have 1980 Evinrude 150 getting hot on port head while starboard stays fine. I have gone through the entire cooling system and have excellent water flow with everything working and operating at perfect temps with the exception of high RPM only port side head gets hot. Replaced the water pump, deflectors, t-stat, bypass valve, and cleaned some minor scale build up from the water passages. Also running the OEM Champion plugs for this motor. Running out of places to look. Could this be a carb problem? Perhaps partially clogged high speed jets causing it to run lean on one side? Any suggestions?

 

[HighTrim]

Re: 1980 Evinrude 150 hot at WOT

the port side usually runs hotter than the starboard, how much hotter are we talking about?? Were you testing it with a thermal gun? If the poppet valves are new, I would pull the lower unit, pull out the t stat assembly, and back flush water from the t stats down the water line, ensuring no blockage.

 

[Striper68]

Re: 1980 Evinrude 150 hot at WOT

Already done this. No blockages with excellent water flow. As for how hot 200 degrees F with the IR gun when the hot horn sounds. This takes about 5-6 mins at WOT. Throttle back to moderate speed or idle and the temp drops within 30-40 seconds and horn stops. Have been through this cooling system from one end to the other with everything OK.

 

[HighTrim]

Re: 1980 Evinrude 150 hot at WOT

For some reason or another it sounds like your port side poppet valve is not functioning properly. If the temp is dropping that quick after 30 secs, it sounds like it is not gettting the cooling water it needs at WOT, aka, the poppet valve. When you idle it down the t stat takes over, opening, allowing the cooling water to do its job. I know you said you have gone over the entire cooling system, but there is something that you are missing or overlooked. Try swapping the poppet valves and see if that changes anything , for experiments sake, or leave it out entirely. It will let you know where your problem lies. I am by no means suggesting to leave out any of the cooling system, everything is there for a reason, but just for testing purposes.

 

[emdsapmgr]

Re: 1980 Evinrude 150 hot at WOT

Have you had the head cover off? What does it look like inside? Any blockages?

 

[scotchguy]

Re: 1980 Evinrude 150 hot at WOT

I helped the original poster with this problem last weekend. By help, I mean I watched him work and drank his beer. Took the port side head off and found calcium blockage and clogged diverters. Cleaned calcium with CLR and intalled new diverters, gaskets and temp sensor. Test run at lake had same results, after 5-6 minutes at WOT, alarm goes off and IR reads port head @195-200 while starboard head is 165-175. Half to three/quarter throttle does not cause any overheating. During test run on lake I was watching the water come out of the ports after the thermostat opens and noticed less flow once we reached WOT. Could the motor position be too high for the boat causing a water pick-up issue? Our other thoughts are port side is leaning out at wot (carb rebuild) or over-revving due to wrong size prop.

 

[emdsapmgr]

Re: 1980 Evinrude 150 hot at WOT

Why not put a water pressure gauge on the engine? A 0-30 lb. Would be interesting to see what pressure it runs at full out. "Normal full speed" should be in the 18-19 lb range stock. If you have it mounted higher, it should be no less than 10-12 lbs for safe operation. When running flat out, check the water flow under the anti-ventilation plate. Where is it. Is it level with the plate, or under it? How much under? If the top water pickup hole is exposed, it will suck air at high speed. Did you check the water passage under the bottom of the water pump? The passage from the pickup screens in the lower, up to the bottom of the pump.