84 johnson 50 hp dies after 10 mins

[kevster954]

I recently bought a 1984 johnson 50hp. I have done a few repairs: replaced ignition switch in controls as it was missing key, replaced fuel pump, replaced water pump impeller/gaskets, oil change on lower unit. I hooked it up to muffs and it ran just fine, i ran it for 45mins to let it warm up and figured she was ready for the river. today when i launched the boat it started ok but had a difficult time idling i had to keep the warm up lever on. the gas in the tank is about 7 months old. another issue is it wasnt pumping much water a few drops but not a stream, when i would raise the warm up lever the flow would increase with the rpm. i left the dock it ran fine i gave it some throttle it would run for 8-10 minutes and die without sputtering just shut off. it would right back up 1-3 more times then wouldnt start till it cooled down.

I know i have a bunch of symptoms. obviously the old gas could do it but it seemed more like a coil or cdi box or maybe i did something wrong with water pump and its overheating. I'm thinking the old gas explains it not idling but it killing like i hit a kill switch while crusing at 1/2 - 3/4 throttle leads me to think its not fuel related at all. when it died i check the primer ball it was still firm, i didn't have a wrench to pull a plug and check for spark when it happened. i was thinking putting new fuel and getting it to idle, and doing the blow dryer test to coils/cdi box. im not sure if its overheating just wondering if anyone had some direction for me.

 

[Chad Flaugher]

I'd still try running it with the gas can vented via loose cap.... Just to rule that out. Process of elimination for sure. Read up here on the forums, problems like this are common. Some good mechanics here (better than me!), somebody is bound to chime in. Good luck!

 

[kevster954]

i gave that a shot as well after it died one of the times.

 

[Chad Flaugher]

Again, I'm not the wisest at outboard engines. I'm more of an automotive guy, just getting into boating. I guess my approach would be to hit the water with every tool in my shop. Like you said, after it dies check for spark, check temps, check voltages... One thing holds true for all internal combustion engines. Fuel + air + spark gets it done. Find what is missing at the point of failure, and you'll know where to start.

 

[boobie]

When it dies, check your spark with a spark tester set at 7/16 " open air gap. You can get them in most parts houses for around $8.00

 

[fireman57]

Sounds like a classic overheat problem. If you have a buddy you can take along and do this safely have him hold his index and middle finger on the head. If he can hold it there for a long count of 5 you are not overheating. If he can't make sure you replace the water pump immediately. I would do this right now actually. Old gas is one of the worst things you can run in these engines. The varnish clogs jets like bubble gum. You don't want to blow this thing up by overheating it. I have an '82 50 that still runs like a rabbit.

 

[rolmops]

There is a little plastic wedge like thingy that must be installed in a slot between the impeller and the drive shaft. It is small and seems insignificant,but if it is not installed, the impeller will just sit loose on the drive shaft in the impeller housing. The only water making it up to the engine is because of the boat speed forcing some water up to the engine and the impeller pumping just a little bit.I would check that and check if the tubing to the power head was put back in the proper way

 

[bonz_d]

Start with the overheat, water pumping issue. Pull the lower back off and check that the vanes on the impeller are all going the same way. Just one in the wrong direction and it won't pump.
I have used 7 month old fuel w/o problem as long as there is no water in it. Only takes a small amount of water to really mess it up. To be safe and eliminate one source of trouble replace the fuel for now. Try and get it to idle. I've a 1983 60hp that is a bear to get started when cold.
Then as mentioned before check your spark and while in there doing that look over all wiring for lose, corroded or frayed connections. Old wire become brittle.

 

[racerone]

Start with a compression test.-------If you are using a plastic fuel tank then check the pick-up tube inside the tank for leaks.