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1982 Johnson 15 HP repair, help needed...

C

CMOS

Regular Contributor
Howdy All,

I've been working on a 1982 Johnson 15 HP that I bought at a garage sale for quite a while. More like NOT working on it more than working on it but...

The short version is that I got her running quite well but after about a minute the bottom cylinder fouls with water. I did previously replace the head gasket but I did so with the power head still in the cowling, so I had poor access to 2 or 3 of the head bolts.

Yesterday I bit the bullet and pulled the entire power head off. I will be pulling the head and checking its surface, then replacing the gasket.

I need help with 2 questions please:
1. Are there any other things I should be looking at that may cause the water fouling (other than the head gasket)?
2. What items (gaskets, grommets) should I replace while I have the power head off?

Thanks for any help.

CMOS
 
Along with the head gasket replacement, I'd suggest you replace the exhaust baffle gaskets and inspect the inner exhaust baffle plate while you have the powerhead off as that is also a common water entry point.
 
joereeves said:
Along with the head gasket replacement, I'd suggest you replace the exhaust baffle gaskets and inspect the inner exhaust baffle plate while you have the powerhead off as that is also a common water entry point.
Click to expand...

Thanks Joe. I was hoping you would comment on this thread.

Are the exhaust plate gaskets the usual issue, or am I inspecting the Inner Plate itself for some problem? Can you expand on this?

Also, I have heard others say to replace some grommet(s) (plural?) on the bottom of the power head. Are these for the 2 water tubes?

Thanks for your help.

CMOS
 
CMOS said:
Are the exhaust plate gaskets the usual issue, or am I inspecting the Inner Plate itself for some problem? Can you expand on this? Also, I have heard others say to replace some grommet(s) (plural?) on the bottom of the power head. Are these for the 2 water tubes? CMOS
Click to expand...

Usually it's a exhaust baffle gasket that fails... BUT... in my 30+ years at the bench, I've encountered more than one inner baffle plate that has a pin hole worn in it. As long as it's right there in front of you with the gaskets, examine it closely, hold it up to a bright light, etc.

The grommet thing...... they're talking about the rubber grommet that holds the top of the water tube (there's only one tube). That grommet, in time will have a tendency to fold over which creates a shut off valve. You would need to remove both the lower unit and the powerhead in order to get at it..... normally a case of wait until it fails as it's a bunch of work and you may find that it's perfectly okay.
 
I think there are 2 tubes up there.-----One supplies water to the power head and the other one is less important.
 
joereeves said:
Usually it's a exhaust baffle gasket that fails... BUT... in my 30+ years at the bench, I've encountered more than one inner baffle plate that has a pin hole worn in it. As long as it's right there in front of you with the gaskets, examine it closely, hold it up to a bright light, etc.

The grommet thing...... they're talking about the rubber grommet that holds the top of the water tube (there's only one tube). That grommet, in time will have a tendency to fold over which creates a shut off valve. You would need to remove both the lower unit and the powerhead in order to get at it..... normally a case of wait until it fails as it's a bunch of work and you may find that it's perfectly okay.
Click to expand...


Joe,

The Power Head and lower unit are already off so I might as well replace that Water Tube grommet, right?

I will carefully inspect that inner exhaust baffle plate as you suggested.

CMOS
 
All,

I have some parts ordered but while reading the OMC Service Manual I have it states to use some OMC "M" type adhesive. Hard to find but I do have some 3M 387 gasket adhesive that I can use.

I also ordered some Permatex #2, per the manual. It states to use this on the "crankcase head in areas shown in Figure 4.64", which appears to be on the stepped area of the round housing that mates with the lower unit (where the driveshaft passes through). Is this correct? To place the Permatex on that mating surface (on part number 385971)?

Next, the manual states to use "OMC Gasket Sealing Compound" on the PowerHead-to-Exhaust housing gasket. Can I use the Permatex #2 here also?

I do not see a torque spec in the Manual for the Inner and Outer exhaust cover plates. Suggestions?

Thanks for any help.

CMOS
 
CMOS said:
Joe,

The Power Head and lower unit are already off so I might as well replace that Water Tube grommet, right?

I will carefully inspect that inner exhaust baffle plate as you suggested.CMOS
Click to expand...

Yes, absolutely replace that grommet... start anew by all means.

Racer... Damn, and not too long ago I held both those tubes in my hand... all I could think of was the tube inserted in the pump. I can't think of what the purpose was for the other one. Engineer job certainty for the following year?
 
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