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1988 Mercury 90HP help

J

juice

New member
Hi guys:

This is probably a dumb question but however.

I have a 1988 Mercury 90hp that one day was great the next it will not even turn over?


totally baffled here.

Any help as where to start?


thanks!!!
 
Need a little more details. Do you hear a click when trying to start, Do you here the starter engage, Can you turn the engine over by hand at the flywheel.

and a lot more ???

Milton
 
Ok. Starter spins , however it seems to spin up to high. It starts to turn the flywheel. Then the starter itself keeps spinning but the gear in the starter goes up to high. The arm the little gear sits on keeps spinning. I can turn the motor at the flywheel. Is my starter pooched?
 
Ok, Will replace the bendix, see how it goes. I bought the motor and was told it was blown. The person I bought it off said one day it worked and the next it didn't. He said it just would not turn over. Turns out from what I have seen so far, is the bendix wasnt spinning the flywheel. He had the baffle plate off and told me he had a bad piston. I have a bore scope, checked the piston with it quickly. I was able to move the flywheel by hand and slowly turned it. It turns very smooth and I slowly checked the pistons over. They seem ok. I put a washer to prevent the bendix ( for now, new one ordered) from going up and spinning the motor. I put the Baffle plate on ( still waiting on new gasket) just to do a quick compression check. I will do it properly if the motor is ok. All 3 pistons have equal 120 psi. I did not put fuel to it I just spun the motor to get a compression check. So I have invested in gaskets and a bendix. I hope it turns out of. What else should I be checking on this motor. I'm crossing my fingers that this is is.

Thanks
 
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Ugh, the above does not give the spec. Anyway, the spec for my '92 Merc 2 stroke 4 cylinder is 130-140.
 
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However, this year, I did a check on mine and now they are 140, 138, 140, 127. Some say along as the differences are not more than 10% and yours being at 120 seems decent; some say anything below 100 is no good.
 
your sounds great


I did this with no fuel, not gasket on the baffle plate. Motor has not run now for 2 months with the baffle plate off for at least a month now. So I am hoping that once the proper gasket is on it will be higher or will that not matter?
 
Hi guys:


thanks for the help, would anyone happen to know what the torque specs are for putting baffle plate back on?


thanks again
 
I have a Merc/Brunswick shop manual for my '92 Merc 40; that has the torque specs for it - you might have to see a shop manual for yours; I don't know what your baffle plate looks like - got a picture? As for gaskets for my carbs and exhaust manifold gasket, I used no sealants with no issues but these gaskets were OE Merc gaskets. Had a bad experience when using an after market gasket for the overhead valve head of my Honda 750 cycle - many years ago.
 
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It’s like this. 50E9D955-B031-4E2F-9FB1-F6132864DED8.jpeg
 
Looked in my shop manual for my '92 Merc 40 4cyl 2 stroke and found this:
From the exhaust (port side of the engine) outward from the head there is gasket, baffle plate, gasket, and lastly exhaust manifold cover that secures all the latter to the head with 15 bolts each torqued to 200 INCH pounds in a certain tightening pattern with loctite Grade 'A' on the threads.
 
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