1990 force 120hp outboard HELP!

jerryjerry05

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Better pics!! :)

From what I see the light scoring and no problem with the rings,
You shouldn't have a problem building compression.

Check the head to see if it's flat or cracked ?
Check the block too.
You can use a metal 3 ft. ruler, even a piece of glass is pretty flat.
The mating surfaces need to be absolutely spotless and smooth.

You can use silicone to make sure the gasket seals right.
 

puffitu

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Thank You Jerryjerry05
when taking the ports off I noticed that some screws weren’t tightened down all the way; some seemed barely over finger tight. Come to think about it I’ve found striped out screws on the intake. You think there may be a leaky gasket(s) on exhaust side also?
 

SkiDad

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Jerry is right, that surface needs to be smoother - that is most likely your issue. I don't think you need any silicone, but if you use some use the correct stuff
 

Nordin

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Looks like it has score at #1 and 2. The rings are partly stuck at the exhaust side.

Most of the score are at the exhaust side because it it way hotter at exhaust and the piston side "melt" depending on bad cooling and the lubrication are not satisfying and the rings stuck.
 

jerryjerry05

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Thank You Jerryjerry05
when taking the ports off I noticed that some screws weren’t tightened down all the way; some seemed barely over finger tight. Come to think about it I’ve found striped out screws on the intake. You think there may be a leaky gasket(s) on exhaust side also?
With a head hung low, and hoping im doing things right; I went and got a comp tester from harbor freight and did and got some bad test results after Ive replaced the head gasket(twice; torqued in sequence the second time). Before, the comp test revealed #1 at 85, #2 at 140, #3 at 155 and #4 at 150. NOW, Im getting 60, 60, 120,120...Plus after removing the plugs I noticed a milky/oily mucky substance on 1,2,and 3.
The engine is trying to run but coughs and backfires. I don't know what to do at this point


He said the rings were free when he removed the port covers.
If the screws were loose?? That would cause a lean condition and make it run poor and hot.
"poor" coughing and backfiring.

If the plugs have water or brown sludge the exhaust gasket could be bad???
That's if the head gasket is sealed right.

The exhaust chest:
This is the worst thing to remove from the motor :) :)
Usually 2-3 of the bottom screws twist off and can be a B to fix when the block is still on the mid-section.
After the screws are fixed, then the reassembly starts.
I've found that it's best to get the mating surfaces of the exhaust and the cover milled as the
edges have been eaten away(not very thick in some places.
You can try to seal them and might get lucky? I think I got lucky 2 maybe 3 times and had no leaks.
They sell some gaskets for the exhaust that are useless, they are thin and don't work unless you double or triple them.
The thicker ones OEM work best. Gasket 8190242 15$
Get from a good source. They might sell them here.
ebay sells them and they can be cheaper but probably not what you need.?


Some gaskets just don't seal good and silicone is needed no matter how clean the surface is.

Did you compare the old gasket with the new?
They also don't always match right??

When I did a couple of rebuilds I bought a few on eBay, trying to save $$
They didn't fit .
 

puffitu

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Thanks Jerryjerry, Skidad and Nordin for the awesome insight and priceless advise. I will be checking the comp again in a bit. I’ll post results. Jerry; thanks for the part but my motor uses a bigger one, unless you think it may work so I’ll keep for spare-otherwise I’ll ship it back. Question, before I re install the four ports; any lubricating spray or any recommendations? Thanks again.
 

puffitu

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I got it running but spitting and sputtering for about 3 minutes in idle @1000rpm
 

jerryjerry05

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Use a sealer on the gaskets, once that seal's been broken it can be real hard to
reseal and can cause a lean burn and "spitting and sputtering" or sucking air.

Once you do any work on the intake side, you should probably reset the air screws on the carbs.

The puddle of water. You torque the screws? use sealer?
Sealer, I use a very thin coat of silicone.
I posted this earlier:
"The exhaust chest:
This is the worst thing to remove from the motor
:)
:)
Usually 2-3 of the bottom screws twist off and can be a B to fix when the block is still on the mid-section.
After the screws are fixed, then the reassembly starts.
I've found that it's best to get the mating surfaces of the exhaust and the cover milled as the
edges have been eaten away(not very thick in some places.
You can try to seal them and might get lucky? I think I got lucky 2 maybe 3 times and had no leaks.
They sell some gaskets for the exhaust that are useless, they are thin and don't work unless you double or triple them.
The thicker ones OEM work best. Gasket 8190242 15$
Get from a good source. They might sell them here.
ebay sells them and they can be cheaper but probably not what you need.?"

Part. Keep it, maybe someone ,someday will need it? Or maybe you can use the inside
pieces?
 

jerryjerry05

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The compression #s are getting better.
Mercury, OMC, Yamaha sell a carbon remover.
Mercury is Power Tune, OMC is Engine Tuner.
Don't know the name of the Yam product.

It does help remove carbon deposits around the rings.
Once the heads back on, spray a bunch in the cylinders and turn the motor over so it coats
all the cylinder and the pistons.
After it sets for 8hrs. respray and then let it set for 2 days and turn over a few times as it sets.

Trying to start: remove the plugs and turn the motor over expelling the excess.
Clean the plugs and fire it up.

Gonna smoke a bit.
After it's been run do a compression test.
 

puffitu

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Hey Thanks so much for all the great help!
i feel I’m making progress over here. I’m thinking of tackling the exhaust gasket(s) replacement but little apprehensive due to the risk of snapping off bolts. If and when I do; whats your advise on how to reset the carbs?? Asking because I’m thinking I may need to do that anyways because seller of the boat had mentioned I should have them reset when I bought it. He also mentioned they were rebuilt fairly recent.
 

puffitu

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Would it be wise to remove exhaust manifold bolts in a sequential manner of does it really matter?
 

jerryjerry05

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Read the top 3-4 posts in this forum.
There's a bunch of hint, tips, tricks to do a lot of repairs to your motor.

U-tube video's. Lots of good video's there.

Doesn't mater when removing the screws.
Just take your time.

Hammer.
Propane torch.
PB Blaster or Krol penetrating oil.

Heat, spray, heat, spray, tap the screws, repeat!!
Then twist the heads off no matter what you do. :)
 

puffitu

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jerryjerry05

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I think you set a record for twisted off screws!!

The odd part is the bottom ones actually came out and these are the ones that usually strip ??

The good part, there is a bit of the screw remaining and you can probably get the rest of the screw out.
 

puffitu

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Lol
yup my neighbor already gave me the “ most twisted off screws” award..! Yeah I’m not concerned about the screws as much as I’d like to correctly identify the gaskets I need. Also, if the exhaust plate is re useable; because it’s taken a beating??. I don’t think the gaskets ever been changed and I’ve dug out a ton of debris from within this thing. Should I loosen the relief valve and flush it all out or...? Thanks
 

jerryjerry05

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The relief valve. Just leave it alone.
The corrosion has already done the damage and trying to clean it won't really help.

I'd already given you the part #s for the gaskets.
 
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