1975 johnson 4hp 3rd gasket repair in 20 years!

binpointlanding

Recruit
Joined
Jul 11, 2010
Messages
1
I only use this motor 2 times annually, but the head gasket keeps blowing out in the same spot. There are points where the gasket is only 1/4" wide and that is where it keeps failing. Is there a better gasket material than the compressed cardboard pre made gasket that I'm using. And yes I'm putting the gasket on dry, and torquing in the proper sequence. At this point, I'm afraid to take out the boat!
 

Vw56German

Cadet
Joined
Apr 24, 2011
Messages
17
Re: 1975 johnson 4hp 3rd gasket repair in 20 years!

The first thing I would suggest is to check the head for flatness. use a steel ruler or small framing square and check to see if there are any areas where the gasket surface is not flat. If it is real bad you will see light under the ruler. You can use a feeler gauge to check for very small gaps like .002" or .003". If the head is not flat you can use sand paper on a flat surface like a piece of glass placed on a towel on your work bench. Use a figure 8 motion to level out the head. Keep checking for flatness until any gaps are gone. One other thing to do also is to use the proper size tap and clean out the bolt holes in the power head. If there is any debris in them the threads could bind or bottom out and you wont have the correct torque, even though the bolt seems tight and the torque wrench clicks.
 

raczekp1

Lieutenant
Joined
Mar 30, 2010
Messages
1,327
Re: 1975 johnson 4hp 3rd gasket repair in 20 years!

i paqid for head flatening 6 $ in auto repair shop.
it took them 10 min work
 
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