120HP Force being smothered on exhaust fumes at idle

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palerider9999

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Oct 9, 2013
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Hey everyone, hope I can get some advice on a this. I have a 1992 120 HP Force outboard that runs great on the open water. The problem is when idling the cowl fills up with exhaust fumes and smothers the engine and it shuts down. If I pull off the cowling I can idle all day long. I pulled the power head and replaced the gasket but the exhaust still backs up at idle. Is there an idle exhaust bypass that is possibly plugged up? If so Can I pull the lower to check it? Thanks in advance for the help.
 
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Nordin

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I am not sure cause I have not worked with that late Force engines.
The power head is a Chrysler/Force power ,head but the midleg and LU is Mercury I believe.
BTW the thread is for a 1992 120 Hp and it has definitely the rubber boot.
 
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palerider9999

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I replaced the exhaust gasket #17 but still leaking exhaust fumes.
 

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jerryjerry05

jerryjerry05

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#17 probably wasn't the culprit??
Right where #1 is on the picture, that's where a gasket goes and it can cause your problem.
Look for the powerhead parts breakdown.
 
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palerider9999

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I also replaced both of those gaskets too when I changed out that plate. I think I may have found why exhaust is entering the cowling. Take a look at the pic. There is supposed to be a baffle on the front/bottom of the base for the motor. Mine is missing and I know it wasn’t there when I bought the boat. I bought the boat and have been trouble shooting this idling issue from day one.
 

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jerryjerry05

jerryjerry05

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That pic is where the motor gets it's air.
And it's missing the cover, that shouldn't cause it to smoke so much it kills the motor.

A motor that's being worked on will smoke a lot more because of the flooding effect of trying to start the motor frequently and not getting it hot enough to burn the oil/gas.
Run it in a DEEEEP bucket, have a fan set up next tothe back and as it runs try to move the smoke away and see if the motor still has a lot of smoke.
 
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palerider9999

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Engine starts right up, runs fine and will idle great with the cowl off. No more smoke than other 2 strokes. I have had the boat for about 5 years now. We usually either take the cowl off to run the engine during docking or just use our kicker motor. Just looking to get this resolved so I can finally fix it since it’s in my garage and not at the lake. My thoughts are exhaust fumes my be channeling up the side up the motor and entering thru that “grill”

There is a fresh air entry port on the back top of the cowling. I will try the fan, deep tub and see if that changes anything.

I will update this post once the baffle is installed and water tested.
 
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palerider9999

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Thanks for all the help and I think I finally figured this out. #13 on this diagram leaks so bad when I put a hose in the lower cowl my water can’t fill it. Also there is a small exhaust port directly under the area where the water pours out the bottom of the mid lower. If any one is having the same issue try to fill your lower with water and watch for it to run out above and near that small hole on the front of the bottom section of the drive shaft housing.
 
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palerider9999

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Sorry, I tried to attach a pic but didn’t go thru. It’s # 13 on the attached diagram. I can’t find this seal anywhere. Part number F178323. Thanks Jerry for the heads up.3646309E-1CDF-401D-970E-5A00B4340AAA.png
 
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