'97 Johnson 150 Rusty Lower Spark Plugs (runs fine)

[levittownnick]

This engine runs well but the lowest spark plug on each bank always gets very rusty. All boating is done in salt water. The engine itself is very clean especially considering the age of the engine. Is this Normal? Does splash get into the housing from rough conditions? The other 4 plugs look good at the end of the season. I just don't know what's happening.

Thanks,
Nick

 

[Bosunsmate]

Re: '97 Johnson 150 Rusty Lower Spark Plugs (runs fine)

Not normal, i do ocean going in salt too, unless you were almost submerging the motor it shouldnt get up that high as the pressure is virtually continually going the other way
Do a compression check.
It could be a lower headgasket leak, exhaust gasket/plate leak or a leaking bottom crank seal

 

[boobie]

Re: '97 Johnson 150 Rusty Lower Spark Plugs (runs fine)

Is the rust on the outside of the plugs ?? If it's on the inside you got some probs.

 

[levittownnick]

Re: '97 Johnson 150 Rusty Lower Spark Plugs (runs fine)

Rust is on the outside of the plugs. The inside of the plugs looks normal. The engine runs well.

 

[Bosunsmate]

Re: '97 Johnson 150 Rusty Lower Spark Plugs (runs fine)

I thought you meant inside.
Mine sometimes get that too from the spray coming in under the bottom cowling i think.
One of the worst jobs i find is removing the powerhead bolts inside the lower cowling motor cover that get lots of this spray, salty moist air flow

 

[rocket72]

Re: '97 Johnson 150 Rusty Lower Spark Plugs (runs fine)

Had a similar problem with my 1996 175 Ocean Pro. Turns out the T-Stat gasket above the row of plugs had a leak. Replaced T-Stat O-ring and solved problem. Hope that helps!