1966 Jonhson 9.5 rust around exhaust cover

[Scram83]

Is this an issue to address right away or wait and see? Want to try to get dads 9.5 running. Found paint peeling and rust on and around the exhaust cover. I did a light brushing to get the loose stuff off before I took the photo. Hasn’t been used in about 30 years. Dad bought it new. Never had heavy use, occasional saltwater. Compression is 60 for both cylinders. Planning to rebuild the carburetor, replace water pump, etc., but thought I’d check about this before starting. Thx!

 

[Crosbyman]

it may have overheated long time ago ?? how is it ? does it turn or stuck solid check gear case for condition

suggest you remove the cyl head and look inside while it is out you can always brush it up and recoat with high temp. paint for cosmetic reasons..

careful not to break head bolts soak in some release agent for a few days

see leroy'S article

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[Scram83]

Don’t think it overheated, but not 100% on that. It cranks. After I got the paint chips brushed and vacuumed I pulled the plugs, added a little oil, and did compression test (60 for both).

 

[Crosbyman]

60 is on the low side but has indicated in Leroy's article these are not very high compression engines. it may come back up after a good run . try some engine cleaner in the fuel . some like SEAFOAM some don't .

my honda snowblower loved it .. it cured the coughing

 

[racerone]

The red appears to be the colour of the primer paint used on these motors.----Degrease the area and paint it.

 

[Crosbyman]

what is strange is the the head bolts ended up reddish color also
yet the one on the right side stained beige/silver

 

[Scram83]

Interesting, it does seem to be a red primer. Definitely some rust there too, I brushed the crusty stuff off before the photo. Hardly a spot of rust anywhere else on the motor, seems in good shape from what I can see on the outside. I guess a cooling water leak did that. I assume nothing catastrophic would happen from this while I get her going and kept an eye on it.

 

[Scram83]

60 is on the low side but has indicated in Leroy's article these are not very high compression engines. it may come back up after a good run . try some engine cleaner in the fuel . some like SEAFOAM some don't .

my honda snowblower loved it .. it cured the coughing

Nice, thx, I’ve been seeing good things about these as I get read up on them. Hope to get it running and bring back some old memories.

 

[racerone]

The parts are all aluminum castings.----Those do not turn a rusty brown.

 

[saltchuckmatt]

Agree with above....I think it was overheated once. You might have issues so pulling the head, inspecting, resurfacing and installing a new gasket might be in order.

 

[racerone]

In my opinion this motor does not show overheating.----Severe overheat changes the colour of the white paint.

 

[tphoyt]

Any chance there was a mouse nest there or something else that looked like it could have been corrosive?

 

[saltchuckmatt]

Looks scorched to me.

 

[racerone]

Exhaust manifold would get very got.----Paint on it is not burned !

 

[Crosbyman]

mouse juice maybe...a big mouse

 

[Diplomasta]

The red color under the paint is not just a primer. It's a specifically designed coating to keep the aluminum safe from corrosion. It is all on the internal water passages too. Do not sand that off. There is nothing you can buy that works better than that stuff. As for the rust, the motor should be sprayed down with corrosion prevention compound (CPC) every 2 weeks to a month. This is basic outboard maintenance that nobody does. A specified care requirement for EVERY outboard.
But if the motor runs, doesn't overheat, and doesn't leak, let it be; unless you're prepared to do a total powerhead breakdown.

 

[racerone]

No need for this " rust prevention " treatment or potion in my area !

 

[Scram83]

Thanks for input everyone. No evidence of mice, don’t know if something was used on it at some point that could have caused the corrosion. I’ll try to get it running and see what I’ve got from there.

 

[oldboat1]

#10 has it right, imo. Remove the head after soaking bolts, resurface the head and replace the gasket. While the head is out on the workbench, replace the t.stat. (The new gasket might improve compression too.)