I have a '92 Johnson 115 V4.
I'm getting my powerhead back from TMW tomorrow. After frying one piston and cracking the cylinder... I'm very confident it will be as good as new, but I'd like to keep the problem from happening again.

I think it was probably caused from no fuel to that cylinder, probably from a clogged jet, right? when I bought the boat it had varnish in the tank from old gas over a year old. I cleaned the tank, then cleaned the carbs with ChemTool and blew air through them with a portable air compressor. (probably not enough psi to be sufficient). The boat ran great the next 2 times I took it out, but the 3rd is when it failed on me.

I'm thinking I have a clogged jet, and the #3 cylinder isn't getting proper fuel. Does that sound right?
Also how can I check to be sure I'm getting fuel to all cylinders so this won't happen again.

I plan on cleaning tha carbs with chem tool and more air pressure this time. How much psi should I use?

There are a few ways. The easiest is to simply take the plug out, disable the ignition, choke the motor and have someone crank the motor while you hold your hand out from the plug hole. You should see the fuel/oil mix on your hand. You can usually see the fuel spraying out with the naked eye.

I would also take the carbs COMPLETELY apart (including the welch plugs if they have them) and SOAK them in berryman's for a few days, clean them out and soak them again until you are sure the high speed and low speed circuits are clean. To be sure, take a can of spray berryman's and squirt it at full pressure through every orifice. If you don't see it coming out the other end, you have found a problem.

BRP makes a "special tool" for removing the jets for cleaning. You can make one with a screwdriver and dremel or belt sander.





What I've done here is cut the end off flat with a cut-off wheel, and used a dremel with a barrel sander to remove about a third of the material from two sides leaving about a third (actually a little less) in the middle. Kinda hard to tell from the pics - that's a flat tab on the end, parallel sides.

Don't try to take the jets out with a regular screwdriver - the slightest damage will change the fuel/air mixture.

j Made the same thing 20 years ago, still have it today and use it regulary,