Johnson 140 Spark plug problems

[kslseed]

Hello,I have problems with mz Johnson SeaHorse 140, the #2 spark plug (top left from behind) is totally fault-up after 5 - 10 minutes run, motor runs, but with low power. The piston looks that some material in the center is eaten up. When I insert a new plug, motor runs fine for 5-10 minutes and then same problem again. My dealer told me to bring the motor in and have new pistons installed, $2000.You can view pictures at: http://www.klempnauer.ab.ca/Johnson%20140.htm Hope for some help.Joerg Klempnauer

[Walker]

No cheap fix for that. Looks like a lean condition caused overheating that started that.

[Dhadley]

Yep, time for piston(s). The biggest thing is to find out the cause of the damaged piston and fix that. What plugs are you using?

[kslseed]

Hello guy's, Iam using NGK R BPZ8HS. The boat came with thus plugs. Why only the one can?

[Dhadley]

Oops! Champions only in that motor!We need to go ahead and get it apart to measure the cylinders. Most likely the crank is OK so it should be just a standard rebuild.Once its back together we can run some tests to determine what actually caused the problem. It may be as simple as the wrong plugs or the plugs may only be one part of the answer.

[kslseed]

Thank you Walker & Dhadley,Thank you for your help. This will be a winter job. Boating season, for me, is over, to much other work and I will leave this engine for christmas.One question, the engine has four barrels, each feeds in a combined crankcase senario or does each more or less feed one cylinder? If one is plugged or not so good that be the problem of to lean feed?Would you have the plug # for Champion?

[Dhadley]

Each barrel feeds one cylinder. Yes, any condition that restricts fuel could contribute to this scenario. I would use the Champion (Q)L77JC4.

[kslseed]

Hello,We put the head back on. Tested all can's from behind top left 110, bottom left 115, top right 125, bottom right 125. This is cold. waiting for new plugs and may do a test run. Any way to test if the problem cylinder get's sufficient mix?