1987 Evinrude stalled out at 4500 RPMs

[s10car]

I someone can help me or give me ideas on this issue I have a1987 Evinrude 90 hp I cleaned out carbs I got good compression on all they are about 120 that is good for an old motor it idles fine in the water etc. so I ran up and down a canal at around 4500 rpms for a good hour and out of no where the motor stop no it shut off like if someone turn off the key I took the cover off and checked the heads for overheat I was able to put my whole hand on the heads it was warm so I try a restart it will not the starter tried to spin the flywheel did not have the power I waited about 1 minute and tried it again and it turn on with no problems and I keep on going no miss fire etc ran fine back now the voltage was high it is charging about between 16 & 18 volt at 4500 RPMs can this cause my motor to shutdown?? thanks to all who can help me

 

[Greg_E]

I'm not familiar with the 90 HP model but I would say that 16 -18 volts is too high. 14.5 would be more in line with larger 1987 engines I have and I assume that would hold true with all the models. Possible regulator/ rectifier problem. On my engine the Tach will usually intermittently malfuction when the VR is failing. I can't say if yours would do the same thing but if the tach is also malfunctioning that could be a clue.
Another possible cause could be a partial blockage of the fuel tank vent. At High RPMs the fuel pump tries to pull more fuel from the tank but because the vent is clogged it creates a vacuum in the tank and the pump can't pull fuel when it the vacuum gets high enough. You said it ran for an hour at 4500 RPMs so it is probably not that.

 

[emdsapmgr]

Please post the model number of your engine. In 1987 OMC made an 88 hp model and a 90 model. They are both 90 hp units and look identical. The 88 hp unit uses a rectifier to recharge the battery. (Also on the 90 hp models that came from the factory without power trim.) On those models it's normal for the voltmeter to show over 16+ volts after running for a while. The 90 hp model (that has factory power trim) uses a more expensive combination rectifier/regulator which will regulate (limit) charging voltage to perhaps 13.5 volts.

 

[wanty9999]

just as a precaution check the main battery cables as they enter the engine cover. My engine did what you described intermittently and I could never figure it out. it would be hauling full rpm and just cut off every couple days. it turned out the wiring harness was arcing near the case and cutting the power. so be sure those wires are all insulated and isolated. Good luck

 

[s10car]

Thanks for the reply back to this problem I am going to check the fuel system since it has the check valve that alot of people have posted to remove it also I will check the power cables to the motor and hope to fix the issue. Now the VR is the one that is water cooled and so far my tach is working thanks again you guys for the advise if you find any other info please let me know.

 

[emdsapmgr]

Hopefully, the engine did not suffer an overheat lockup. If one piston overheats in a cyl, it can swell up and lock in the cyl bore. It will stop the engine dead and the starter won't be able to rotate the flywheel will the engine cools down again. This is an unusual type of overheat, where the engine is cooling, but one cyl is running very hot. Could be from debris in the cooling system or a rubber water diverter out of place by that one cyl.

 

[s10car]

Hi emdsapmgr I did not think of that but I did not have the alarm go off the water pee is good but like you said it only takes one for to lock up but after that when I got home I did a compression test and still I had 120 on each cyl thanks again if you hear anything please feel free to post thanks to all

 

[s10car]

Hi to all that have help me with this issue I had sometime to get on the motor again and open it open to see what is going on what I have found inside is alot of build up of sand around the cyl. and they removed the T stats and the pressure relief valve so it is not cooling the motor correctly I hope this help fix this issue I we let you guys know thanks.