1993 Johnson 140

Hey new here,

I have a question hoping for some direction. I purchased a boat last summer with a 1993 Johnson 140 on it. I've had multiple issues all minor like water in gas, kill switch short, fouled plugs , stator went out, dirty carbs. I have been able to repair all of that but now I have a strange issue i cant figure out.

Last weekend i put the boat in the water for the first time this year and it fired fine and ran well for 30 mins. Then I lost all power to the engine. It continues to run but even with the throttle wide open it putts along. Its almost like it over heating and has a rev limiter but i do not get an alarm sounding or anything. Its an older boat so it does not have a temp gauge. I am finding all kinds of information from it being the power pack to the water pump (even tho I have a strong stream of water being pump out the tail. Any guidance woudl be greatly appreciated....

Are you saying that the engine rpm hits full throttle and the boat goes nowhere... or that the rpm does not increase when you advance the throttle?

Best to start with the basics......

Check the compression. What are the psi readings of all cylinders?

With the spark plugs removed, check the spark which must jump a 7/16" gap with a strong blue lightning like flame... a real SNAP!... Does it?

If the above two areas are as they should be, I'd suspect that debris has broken loose and affected the carburetors, however there could easily be other causes.