1994 Force 120hp - Exhaust leak

[MarcusMensrea]

Hoping someone here might have worked on a 1994 Force 120 at some point.

The issue is that I have a major exhaust leak under the cowling. Decided to take it to a mechanic as it looks like the power head has to come off and it feels a little beyond my technical ability.

The leak appears to be coming from around the plate kit spacer area. The diagram found here:
http://www.boats.net/parts/search/M...00001 THRU 0E093699/CYLINDER BLOCK/parts.html

Shows part 45 as a gasket for the spacer.

Seems straight forward, replace the gasket... however there is nothing listed for a gasket part anywhere that I can find to go on the under side of that spacer plate for this engine.

The model changed up in 1995 and the diagram there shows the adapter plate in more detail and with gaskets both above and below the spacer.
http://www.boats.net/parts/search/M...HRU 0E138599/ADAPTER PLATE - UPPER/parts.html

The diagrams for the gaskets do not look the same and as they don't have the same part number and there was a pretty significant change in engine design between Force 1994 to 1995 I don't think they are interchangeable.

So after all that, my question is, is there a gasket that goes below the spacer plate? If so does anyone know where I can get that part?

Thanks!

 

[MarcusMensrea]

Looks like the links in the narrative didn't work. This is the link to the 1995 Force 120 adapter plate diagram.

 

[pnwboat]

On the 1994 and earlier motors, there is no gasket under the spacer plate. It's simply a thick bead of silicon RTV. I would double check to make sure it's not the exhaust boot that's leaking. Item # 27 in the diagram below. The exhaust tube item# 16 bolts directly to the bottom of the spacer plate and also has a bead of silicone RTV on the sealing edges. There is also a rubber foam gasket item#17 that helps seal the exhaust gases from entering the cowling area. You can ususally make one out of rubber foam window weather strip or similar material.

http://www.crowleymarine.com/mercury...cfm?mdl=SMMDAJ

Forgot to mention that to get to items 16 and 17, you have to remove the block from the lower unit. Check the idle exhaust boot #27 before you do anything. To replace the boot, all you have to do is remove the rear cover #22.

 

[MarcusMensrea]

Yeah unfortunately I already changed that exhaust boot. First thing I did.

Last time it was in the water I saw the exhast (and some water!) coming from the area of the spacer plate towards the front of the engine.

The mechanic is having a difficult time getting the block off the lower unit. Everything is unbolted but the engine isn't coming off. I saw the bead of black silicone (or maybe some other substance) and the mechanic thinks that at some point someone may have used epoxy rather than the upper gasket part #45

I have part #17 as well and intend to replace that if the power head will come off.

Wish me luck, I get to force the motor off because the mechanic is afraid of breaking either the block or the spacer plate.

Other than the bolts holding the motor to the spacer plate is there anything else holding the engine onto the lower unit? I don't have to remove anything from inside the lower unit first do I?

 

[Frank Acampora]

DO NOT put a thick bead of silicone under the plate. Since no exhaust is at that point except when the engine is sitting low in the water and the backpressure relief is working. Either use nothing at all because there is not enough exhaust pressure to appreciably leak or use a very thin coat of silicone. The underside of the plate has a groove which directs some water around the internal exhaust downtube to help cool it. A thick bead will fill in the groove and impair downtube cooling.

It is these little things that separate the really good mechanics from the rest.