1985, 50HP, Johnson starting problems

[mwd]

I have a Johnson 1985 50hp motor that I have been experiencing problems with. The motor starts fine and runs great when I first get on the lake. If I run the motor for about 15 - 20 minutes, shut it off, fish, then try to restart it, it will not start. This does not happen when it is used for shorter periods of time (5 - 10 minutes). When this happened, I pulled the plugs and both are wet. I have squeezed the full bulb and it is hard. I have checked the spark and it is present. I have installed new plugs. This results in a bad day on the lake. Used the trolling motor to get back to the ramp. Load the boat and go home. When I get home, put the ear muffs on the motor to see if I can find a problem. The motor starts fine. This has happened several times this year.

Any ideas or suggestions are welcomed.

 

[jtexas]

Re: 1985, 50HP, Johnson starting problems

does your boat leak, by any chance?

Just a hunch...back of the engine just below the cowling - the two exhaust pressure relief ports there have to be open...if they get submerged she'll have a hard time starting.

 

[mwd]

Re: 1985, 50HP, Johnson starting problems

Don't have any leaks. When the problem happens, it appears as if the kill switch on the throttle contol panel is pulled. After a period of time, loading the boat, driving about 30 minutes, unloading the boat in the garage, the motor will start. It may smoke and run rough for a few seconds, but smooths out as if there wasn't a problem.

 

[jtexas]

Re: 1985, 50HP, Johnson starting problems

throwing the kill switch disables spark.

Maybe you just need to fish for another half hour ......

sounds like she's flooding, maybe running rich. Possible culprits: leaky primer valve, leaky float valves. when was your last carb rebuild and did it include replacing the float valves?

 

[mwd]

Re: 1985, 50HP, Johnson starting problems

I like the way you think and agree about fishing longer, but some days I don't have that option. I did have the carbs reworked in March this year and everything worked great until the last couple of weeks.