1977 Johnson 85hp Javelin engine problems

Devo135

Recruit
Joined
Aug 24, 2013
Messages
2
Hello guys, I am new to the forum and new to boat ownership. I recently acquired a bass boat with a 1977 Johnson 85hp Javelin. It was a steal of a deal and overall, was well maintained. I've had the boat out on the water 4 times since I bought it and today, the problems started. Before I get started, I should point out that I'm aware the motor needs new plugs. I have not changed them yet, though I am confident that new plugs will not solve the problem that has come up. I suspect that a carb cleaning is also in order. Fresh gas at the proper mixture was added prior to hitting the water today. Unfortunately, my day of fishing did not last long. Here's the problem.

The motor starts up great and runs strong. I have not yet had a compression test done but I suspect that it will be fine in that area. The motor dies at low idle. Once you do get it started, it dies every time you put it in gear. Sometimes it will go into gear and start moving but then you have to "Baby" the throttle approximately 1/8th of an inch at a time. When that happens, there is a serious delay in power almost like the engine is bogged down however; in about 10 seconds, it will correct itself and then run out fine. None of these issues exist at top speed. Once the throttle is at max speed, the boat runs like a dream. If you are at top speed and lower the throttle, the engine will die. Once it dies, it will not start again for several minutes. If you use the choke to start it, it will only increase the RPM's once and awhile. With the choke wide open, it acts as if no choke is applied and then dies. The next start it will start "Screaming" and that is your chance to lower the idle and hope it goes in gear. Most of the time it will just die if you lower the idle.

After several failed attempts, I pulled the fuel line, re-connected it and pumped the primer. When I do that, it starts right up. The engine almost sounds like it is out of gas or being starved of fuel. I am going to change the fuel line and the plugs and get the carbs cleaned and rebuilt go from there however; it was suggested that it sounds like a bad coil. Thoughts from the experts?

Thanks,

Ryan
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
Re: 1977 Johnson 85hp Javelin engine problems

Fuel pump diaphragm ruptured??? Pull off the hose that connects the fuel pump to the crankcase (pulse hose) and give the primer bulb a squeeze. If gas squirts out the disconnected hose, diaphragm is shot. That can cause your poor idle, and starvation. Fuel pump can be rebuilt, get the kit here at iboats.
 

JRegier

Petty Officer 2nd Class
Joined
Aug 17, 2013
Messages
136
Re: 1977 Johnson 85hp Javelin engine problems

My motor wouldn't want to idle and seemed to hesitate a bit if I increased throttle slightly, my plugs were gapped a .038, they called for .030 setting.
 

Devo135

Recruit
Joined
Aug 24, 2013
Messages
2
Re: 1977 Johnson 85hp Javelin engine problems

Turns out the cover on the inline fuel filter had a crack in it and was leaking fuel / sucking in air. Problem solved. Thanks for all the input.

Ryan
 
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