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9.5hp inner exhaust plate has a small fuel leak

S

Snapper Fisho

Regular Contributor
Hello, I have an Evinrude 9.5hp that runs well without hood on but dies with the hood and noticed a small fuel/oil mixture leak from the bottom on the inner exhaut mainfold plate that attaches to the port side of the crankcase. I pulled it apart and it wasn't obvious where along that gasket when inspecting. I have pics to show the leak along the bottom. I have started to clean the insides and remove the old gasket.
Has anyone seen a leak from there before on these turtle motors?
I also inspected the lower oval exhaust seal and it looks quite good but has a couple of pressed in curves on both sides, I assume from the shell. This part is no longer available here in Australia and neither is the inner exhaust plate gasket part no: 309709. The gasket is available on this site though.
Is there a gasket maker I could use instead? A local marine place said to use Hylomar Blue.
Any thoughts from the very experienced here please? Thanks
 

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There are several known problems that cause those motors to smother on their own exhaust with the hood on.

Rynning in a barrel---get it out of that barrel and onto a boat.
That flap seal can be a minor problem under certain conditions
Torn Shift rod boot. Up inside the exhaust housing. This usually is the problem.
Missing seal from top of the water pump. Or missing extension tube f long shaft.
 
Thanks fdrgator. I forgot to mention I did check the shift rod boot seal and also the seal is intact on top of the water pump. All bolts/screws came out well fortunately.
I have run another 9.5hp in that half cut out plastic container with the hood on without any issues. The only bit that has me thinking is this inner gasket seal as it leaks a steady drop of fuel/oil every minute or so where I put the absorbent paper or it's the lower oval rubber seal where it is pressed in, at two sections and no longer sealing effectively. I have ordered the gasket for this inner plate and now hoping this is the culprit once I receive it and reinstall everything back.
 
With this 9.5hp motor design, each time you want to check the shift rod boot seal you have to separate the exhaust housing from the powerhead because the metal plate that holds it in place with 3 screws will not come out otherwise, due to the shape of the copper water tube and the way it sits in there.

Have to break the gasket seal and I can't source that oval powerhead to exhaust housing gasket anymore in my part of the world. Getting it from the US is too expensive, so does anyone have experience with a good gasket maker to use when reattaching the powerhead again to the exhaust housing? Thanks.
 
I'm going to try Permatex No. 1 Form a gasket but before I do, what about Gel Seal/Loctite 518 for reattaching exhaust housing to powerhead?
Have used this successfully to repair 9.5hp powerheads with running issues that have leaked fuel-oil mixture between the crankcase halves.
 
Update: I used both the Permatex No.2 but it did not seal perfectly.
I then used the Loctite 518 flange sealant and so far no leakage between the powerhead and exhaust housing.
Good to know I can get around the gasket here.
 
Finished product after replacing shift rod boot seal, the inner exhaust manifold plate gasket and reattaching the powerhead to the exhaust housing with Loctite 518. No more exhaust leak with my 1973 Evinrude 9.5hp. Runs and idles fine with lid on! :)

1973 Evinrude 9.5hp.mp4

drive.google.com drive.google.com
 
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