1990 force problems

Hosephwi

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Jul 10, 2022
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So I have a 1990 bayliner with a force 90 outboard. Got the boat for free after my father in law passed and to give a whole history for better advise.

Boat was purchased brand new and they stopped using it in 1995. It was stored and never touched till 2019. I got it running without doing anything but fresh fuel and took it to a mechanic to give it a tune up and new water pump. The shop said it didn’t need a new impeller so stupid me thought ok.

First time out of course it overheated and we had to paddle back to the launch. Changed the impeller myself which I should have done in the first place.

After that we had it out with no real problems I just thought it should have more power. Did’t get to use it last year but this year I took it to another mechanic that works on older boats and took it out last weekend having all the power back and loving it. Got about ten minutes in at wot and the rpm dropped from about 4200-3300 no loud noises just lost rpm. Then started shaking the boat and eventually died in the water. Got it towed back to the launch and at home I replaced the fuel pump diaphragm and got it started with new plugs and cleaned the carbs. The only way to get it running is to have the idle screw all the way in and sometimes starter fluid does the trick. Checked the butterflies synced and all the wiring good. It misses and spits and runs like crap. Still won’t go above 3200rpm at wot either. I need a new bulb for my spark tester so I can’t speak to that right now but any ideas on my next steps? What does it sound like? See video below

 
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racerone

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Dec 28, 2013
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Sounds horrible to me.-----Stop the revving and hoping.-----Do a compression test.----Post your numbers.----Forget the blinky tester.----Does spark jump a gap of 3/8" on a test device in open air??
 

jerryjerry05

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May 7, 2008
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Compression test, spark test.
The video sounds like it's running on 2cyl.
How much oil you adding to the gas?
 

Hosephwi

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Jul 10, 2022
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Sounds horrible to me.-----Stop the revving and hoping.-----Do a compression test.----Post your numbers.----Forget the blinky tester.----Does spark jump a gap of 3/8" on a test device in open air??
Top cylinder no spark middle and lower good. Top cylinder 120 middle 60 bottom 70 on compression tester. And I did this test cold so I may have to figure out the spark problem first and do the compression test again.
 
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racerone

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Don't waste your time on the sparky things.----Take the cylinder head off.----I do not think this motor will run without major surgery.----You will not like what you see.
 

Hosephwi

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Don't waste your time on the sparky things.----Take the cylinder head off.----I do not think this motor will run without major surgery.----You will not like what you see.
I’m thinking the same. Maybe have some fun this weekend taking things apart.
 

jerryjerry05

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Usually 60-70 on the bottom 2, could be just a bad head gasket.
Take the head off, BE VERY CAREFUL WHEN REMOVING THE BOLTS!!!!
They've been there for maybe 30+ years and they tend to get stuck and break off.
PB Blaster, a propane torch and patience, patience, patience!!!
One time it took me almost 2 hours to get 2 bolts free, one broke anyway :(
 

Hosephwi

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Jul 10, 2022
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Oh and the bolts came right out easy peasy. Gonna order a new head gasket recheck compression. Wondering if I should just order the coil while I’m at it?
 

Hosephwi

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Jul 10, 2022
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Head gasket repair was the trick. All cylinders at 120psi cold. Got it revving up to 5000+rpm and there is a strange vibration coming from the motor.

 

jerryjerry05

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Sounded good to me.
A no load of 5000rpm really doesn't show much.
A loaded rpm would be much better, in the water, boat loaded and gassed.
Then try to hit 5500 at wide open.
 
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