Fuel leak on Force 90 hp 1991

BarryK3

Seaman Apprentice
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Dec 6, 2017
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48
Hi all,

I am a new owner of this motor. I have an green oily residue on my engine with some puddles under the carbs and minimal green buildup near the fuel inlets on the carbs. I recently rebuilt all of the carbs but did not change the fuel lines on this old motor (mistake). I assume the green is 2 stroke oil (although it is blue in the bottle?) The carb fuel lines have spring clamps, not hose clamps. I an considering changing all of the fuel lines. Are rubber automotive hoses OK? Best clamps to use? Does anyone know the size on the lines offhand? Would you also change the fuel pump gaskets? I don't see the exact source of the leak, everything is oily.

The engine runs great wide open, no problem with power at all. Idle is a bit rough but not bad, probably normal for a 2 stroke. I don't have any experience with 2 stroke outboards, maybe they are always a bit oily? We used to have a Mercruiser I/O V8 in my youth.

Thanks!
Barry
 

jerryjerry05

Supreme Mariner
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May 7, 2008
Messages
17,924
I believe the fuel lines to be 1/4" or 5/16"

Yes automotive is ok.
BUT!! Ethanol can hurt the older hoses so try to fine E rated hose.

​The spring clamps were ok on the motor when it was new.
They seemed to work best when left alone for a time.
I replace with stainless steel when the spring clamps come off.

If your tearing the pump down?? then don't just replace the gaskets.
Rebuild the whole pump.
You can have 2 different pumps on the 1990.
​One is square(Mercury) and the other is shaped like the number 8 (Chrysler/Force)
Kits can be found here to fix the pumps.

The "green" oil could be a storage or fogging oil??
​I'd clean it off and let it dry and then spray with WD-40 and on the moving parts some White Lithium Grease.
​A thick/stiff grease will cause problems down the road.
No Anti-Seize.


"Rough Idle" could be the carbs are dirty and need reset??
(reset) that's the air screw on the carbs.
​Read the first few posts in this forum.
​Do a compression test and post the results.

​The first few posts in the Force forum have tip and procedures that can help.
Don't attempt a tune up.
The only thing that you can do is change the plugs.
​Don't mess with the timing.

​Good luck and Welcome
 

BarryK3

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Joined
Dec 6, 2017
Messages
48
Thanks for the reply!

This is the green oil accumulating in the engine well and under the carbs: https://photos.app.goo.gl/FJURiX8OG2w6Hejy1
It must be a combination of 2 stroke oil and marine grease?? The color is similar to gear oil. I can't imagine it is coming from the lower unit. I just replaced all of the lower unit seals and it finally is not taking in any water.

How much oil accumulation is considered normal?

Impeller and water pump housing a fairly new, prior owner replaced them just before sale. They look fine.

Old hoses and spring clamps: https://photos.app.goo.gl/AO3cxVf0x2jTwqxl2
I'll go ahead and replace the fuel lines and clamps and see how it goes. I have the "figure 8" fuel pump. I think the fuel pump is OK.

I recently did a full rebuild of all of the carbs. Float height is set to spec. Idle mixture screws are all about 9/16 turns out. That gives it the smoothest idle and off-idle that I can get. The engine runs perfectly above 2000 rpm, very smooth and strong. WOT is great, about 36 mph.

Power head was supposedly fully rebuilt in about 2004.

Compression, engine cold:

Cyl 1 125 psi
Cyl 2 135 psi
Cyl 3 135 psi

Combustion chambers and ports are full of carbon. I looked at them with an inspection camera. I have been using Seafoam spray through the carbs and Seafoam at 1 oz/gallon in the fuel. Carbon is decreasing slowly.

I checked the timing and it is fine.

Boat is being used in salt water now. Prior owner claimed fresh water only. I just noticed this salt buildup at the top of the cylinder head near the thermostat:
https://photos.app.goo.gl/1F8IvxP21vNRSvRO2
https://photos.app.goo.gl/UCSZCiwJ2e1EYFxP2
Is this a cause for concern?


Thanks again for the help, really enjoying the boat!
Barry
 

jerryjerry05

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May 7, 2008
Messages
17,924
The 9/16 is not right.
You set it in the water?
Factory suggested on the 85/90 to be set at 1 turn out.
​There is a post in the top 3 posts covering the carb set up.

​Hoses/ clamps: I've never seen those hoses/ clamps go bad.
​IF?? they did start to leak? just replace the clamp with a stainless steel one.

​Pic #1 Oil: clean it up, I use Dawn soap or any good soap..
​Then if it comes back? look for a leak somewhere?
There's no way that gear oil can go up into the engine compartment.

​When you squeeze the ball?? does it get hard? and stay hard until you start the motor?
It should go soft after you start.
The fuel pump has a rubber diaphragm that can split and leak fuel.

​Seafoam: DOES NOTHING!! Does not remove carbon just a waste of $$$
​I tested SF against Power tune.
​One carboned piston in SF and another in PT.
​The next day the one in PT the carbon just melted away.
​The SF did nothing. Carbon still there.

Carbon: do a de-carb. Mercury sells an item called Power Tune, Johnson sells Engine Tuner.
Yamaha sells their own product. All the same.
Use it according to instructions.
​On real bad carbon I put it direct into the cyl. and let it set for 2 days, turning it over every so often and adding more as needed.

​Additives: Ethanol stabilizer and Sta-Bil are the only things I'd add to my fuel.
Then only if the motor's gonna set for extended periods of time.

​Last 2 pics: that area, is probably a bad seal.
Nothing to worry about as the head gasket is further in the head.
You could try to get it apart and reseal? I'd leave it.

The compression: 10# isn't too bad.
​But keep an eye on it.
The decarb might bring the comp back up??
If it does? then do a de-carb every 3-4 mo. (usually done once a year)

Carbon is the killer. On the stbd side of the motor is a recirc system.
Take it apart and see if the screen is full of carbon??
​Don't try to scrape it clean. PT in a jar and soak the screen until the carbon is melted.
 

BarryK3

Seaman Apprentice
Joined
Dec 6, 2017
Messages
48
Thanks again Jerry!

Yes, the fuel line ball gets hard when you pump it. No obvious leak.

I will pick up some Powertune tomorrow.

I adjusted the idle mixture screws on the water. It ran rough with 1 turn out. I got it to the best setting that I could get. I will readjust after the decarb. Again all carb components are new and float height is correct.

I will also clean the recirc. system.

It's great to have someone with experience to advise!

Barry
 

BarryK3

Seaman Apprentice
Joined
Dec 6, 2017
Messages
48
Hi Jerry,

I changed the fuel lines and ran a can of powertune through the carbs. Then we ran the boat many hours last weekend. It runs perfectly at partial to wide open throttle. I'm getting 37 mph at WOT with 90 hp on an 18' Bayliner Capri, 1991.

But, there is a lot of smoke in the cowl at idle and the oily residue still builds up. So, it seems to be an exhaust leak, not a fuel leak. Would that explain the green oil everywhere? The smoke is only visible when on bypass. No obvious smoke around the powerhead when running on the muffs.

With the boat in the water the rpm picks up to about 1300-1400 at idle in neutral with the cowl off, then drops back to 1000 with the cowl on. Rpm is about 750 in gear. Idle is also about 1300-1400 on the muffs. Maybe this also explains why I had to set my idle mixture screws to 9/16 turns instead of 1 turn, to compensate for the exhaust getting sucked back into the carbs??

I can't tell exactly where the exhaust leak is coming from. More smoke on the exhaust side of the powerhead and maybe under the powerhead. Rubber exhaust boot seems to be intact, no water leaking from here. Lots of water flow out of the 2 holes in the back when on bypass. It could be coming from the exhaust cover or from under the powerhead? Powerhead has blue rtv under it where it connects to the midsection, under the spacer. There is also a small amount of water leaking around the gasket for the exhaust cover plate on the port side.

I did not open up and clean the recirc system on the intake side of the motor yet.

I checked the gear oil in the lower unit and it is perfect, no water or milk. The new seals are working.

Thanks,
Barry
 

jerryjerry05

Supreme Mariner
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May 7, 2008
Messages
17,924
The exhaust leak ??
I've found the rear port side of the motor could be leaking or (the worst place ever) the bottom seal where the
exhaust tube meets the bottom of the mid section housing.
That's a rectangular gasket about 3/16" thick.
It can get twisted and leak.
Pray it's not there!!
 

BarryK3

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Dec 6, 2017
Messages
48
Thanks Jerry!

Would you try replacing the exhaust cover gaskets first or get ready to remove the powerhead and replace all of the exhaust gaskets?
 

jerryjerry05

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May 7, 2008
Messages
17,924
IF?? the actual powerhead isn't leaking??
Then You could do more damage trying to reseal the whole motor.

Just to be sure???Try to figure out the where the leak is.

Then pull the head and replace the bad gasket.

That gasket , new, can be found.
Start looking on e-bay, I saw 3 new on there.

When installing use a bit of sillycone to keep it in place.
 

BarryK3

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Dec 6, 2017
Messages
48
Today I ran the engine in the driveway with the lower unit in a large water bag instead of on the muffs, to cause the bypass to open. I had the water level well above the ventilation plate. I could not detect an exhaust leak from the powerhead itself or from the spacer plate area. The exhaust boot also seemed to be intact.

The exhaust smoke was coming from lower down, probably from the gap between the rear cover of the motor leg and the leg itself.

There was water coming out of the 2 holes at the back of the leg, from the exhaust boot but not much smoke.

I can see that seal #21 is twisted.

Boot #27 seems OK. I will take the rear cover off to inspect more carefully.

Gasket #4 can't be checked with the powerhead on.

Next steps??

Thanks,
Barry
 

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jerryjerry05

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#21 only keeps the water from coming in, has nothing to do with sealing the exhaust:(
#27 check the underside for cracks? otherwise it's not leaking exhaust. :(
The real unfortunate thing is #4 is probably bad and needs to be replaced.:( :( :(

It can be done if you have a way of lifting the powerhead up far enough to clear the top of the mid section.
 

BarryK3

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Dec 6, 2017
Messages
48
Thanks again Jerry!

I will remove the rear cover today and inspect #27.

I can rent an engine hoist to lift the powerhead. What is the safe way to lift? There are three 1/4-20 holes in the flywheel. The shaft/nut holding the flywheel is about 3/4". Will a Mercury lifting eye fit the shaft? Or is it OK to lift with 3 x 1/4-20 bolts and a fabricated plate with eye?

There is a gasket between the powerhead and spacer plate which looks to be intact. There is blue RTV between the spacer and the motor leg which also seems to be intact. Is this the correct way to seal the junction? I guess I will have to remove the RTV and re-seal.

Also, where can I get a factory manual? I only have the SELOC now.

Happy holidays!
Barry
 

jerryjerry05

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Factory manual: e-bay would be a good bet.
If your not leaking exhaust at the base gasket?? then don't worry about taking it apart.
You can't take it apart anyway until the powerheads been removed.

The exhaust tube and adaptor plate comes out when you remove the powerhead.

You don't really need a manual if you take a bunch of pics as you go.

Yes the 1/4-20 screws on the flywheel will hold the motor.
I only use 1 of the holes with an adapted L-bracket.

Just undo the linkage. Then the wiring harness at the junction. Then the fuel lines.
Then the air inlet under the bottom carb(has 4 tiny 10/24 x 1" screws) when removed it makes it way easier to get to
the nut on top of the shift rod.
There is a of 3/8-16 bolt under the front intake that can be hard to reach, I just leave that one out when reassembling..

Remove the rear cowl, there is a nut that's hard to get at.
The bottom cowl can stay on.

The less screws you remove the less the chance of stripping/ breaking them.

Good luck and don't be afraid to ask.
Merry Christmas
 

BarryK3

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Dec 6, 2017
Messages
48
Hi Jerry,

I took the rear cover off the other day and checked the exhaust boot (#27). It is intact. Probably was changed fairly recently. I was surprised to find that it connects to the interior of the motor leg and there is no valve or anything. I put my inspection camera into the interior of the leg. It is very clean in there, no oil or carbon. I just don't understand the exhaust gas flow when the boat is off plane and the water level is high. How exactly does the exhaust get into the interior of the leg and then out the boot? If gasket #4 is leaking, wouldn't the exhaust just go into the motor leg and then out the boot? Or does it get in between the rear cover and leg and then into the cowl?

I was able to adjust seal #21 and get it into a correct position.

I took the boat out on New Year's Day and had a good run (warm weather here in So. Cal.) It ran really well both at idle and at cruise. There is still a lot of smoke with the cowl off. I just can't tell exactly where it is coming from. It just seems to be near the base of the power head or from below the power head. Maybe it's even smoking oil on the engine rather than exhaust??

I still have the green oily film on the engine and at the base of the cowl. It seems to accumulate the most after trailering home (about 40 min) with the engine tilted. I see a bit of it on the port side of each of the 3 carburetors. I did change all of the fuel lines recently and the clamps are OK. Maybe the carbs are leaking in the tilted position? I rebuilt all 3 recently. I'm still not sure how blue 2 stroke oil would turn green.

I removed the spark plugs afterward and checked the cylinders with the inspection camera. There is still significant carbon, but it is definitely better after the Powertune treatment!

So, I'm not sure what to do at this point. The engine is perfect at cruise and wide open. Idle is decent. I hate to mess up a good thing by breaking bolts, etc. I think the Powertune helped a lot. I should treat it a couple of more times probably. Spray inside the spark plug holes?

Would you still recommend opening the cylinder drain/recirc system and cleaning or replacing the screens? Might this help with the smoking and oily film on the engine? Also, there is a short hose between the fuel pump and "cylinder drain plate". What does this do?

I hope your New Year is going well.

Thanks,
Barry
 

jerryjerry05

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May 7, 2008
Messages
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If you adjusted the gasket under the rear cover and it was twisted??
Then that could have been the trouble????
Even with the seal twisted , you shouldn't get much exhaust in the cowl.
The majority of the smoke should go out the exhaust snout on the bottom of the cavitation plate.
The rubber boot at the rear of the mid section is for excess water and exhaust.
If the mid section seal is allowing exhaust up it has no way of escaping but the plenum under the carbs.
That gasket is primarily there to keep excess water from getting into the motor.
It allows some but if it wasn't there, it could allow so much(say when you slow down fast) to flood the motor.

IF??? it's running well enough??? then don't do any thing more.
It's not an easy job to replace the gasket on the exhaust tube.

The carbs will leak some fuel when tilted.

I'd still do the recirc system clean.
The de-carb get s a lot but it also breaks up small pieces and they get caught at the screen and can cause problems later.

The hose is part of the recirc system.

De-carb: yes spray in the plug holes, tilt motor up and spray and then turn the motor over 1/2 revolution.
Then add more.
It will be a bit hard to start but the excess carbon will be gone.


The weather here?? SUCKS!! 35d BRRR
Other than that my New Year is just great.
 

BarryK3

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Dec 6, 2017
Messages
48
Thanks Jerry,

I will clean the recirc system and continue to decarb.

I received the tilt/trim and will begin working on that project. I will post some questions on my other post.

I hope it warms up soon for you!

Take care,
Barry
 

jerryjerry05

Supreme Mariner
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May 7, 2008
Messages
17,924
Me too.
If you can't find the screens??
Sometimes on e-bay??
I have them. You pay shipping and what I have into them.
 

BarryK3

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Dec 6, 2017
Messages
48
I had to order some parts for the power trim and they also had the screens, very inexpensive. Thank you for the offer!
 
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