9.9 johnson cooling problem

[matt88]

I have a 1974 9.9 johnson that seems to be overheating. I just installed a new impeller about a week ago and since then it has done a lot better but I think I may have a blockage somewhere. The hole in the back directly under the powerhead only pumps water while under a load (no peehole on this engine) and when its pumping the water goes from very warm to almost scalding hot. I realized I had a problem yesterday when the motor wouldnt start back on the water and the engine felt a lot warmer than I thought it should. I took the plugs out checked for spark put them back in and luckily for me it fired and I got back to the dock. Other engines I have owned pumps water from this hole all the time and it is always almost lake temp not real hot like on this engine. Looking for suggestions,thanks in advance and sorry this was so long.

 

[matt88]

Re: 9.9 johnson cooling problem

I forgot to mention that when the engine is running the side opposite of the shifter on the power head is a lot warmer than the other side. The shifter side of the powerhead stays really cool while running.

 

[Rick.]

Re: 9.9 johnson cooling problem

What you describe sounds to me like your thermostat is malfunctioning (stuck shut). As a temporary measure you could pull the stat and try running it without one to see if that fixes it but I would probably get a new stat and gaskets and just replace it anyway. You can visually check for blockages when you have the head off. You better do something soon as running your engine that hot is going to cause you other problems which are time consuming and expensive to remedy. Best of luck. Rick.

 

[kbait]

Re: 9.9 johnson cooling problem

'74-'76 had no pee hole, and the water will only come out the exhaust relief after the t-stat opens, and just misting at idle. If you can idle slow for a minute and can grasp the base of a spark plug for 2 seconds, you're probably good. The heat is from the exhaust, as it's directed to the port side after combustion.
I agree that your t-stat is partially blocked or faulty, by cool, then scalding water described.
Was your old impeller intact? Sometimes an impeller vein tip can get caught up and block the flow.. maybe at the t-stat??

 

[matt88]

Re: 9.9 johnson cooling problem

Yes it was the t-stat. I appreciate it guys. I do have another question on this engine though. I was working on it tonight and noticed one of the coils throwing sparks to the part of itself thats bolted to the engine. Would water splashing up from the muffs cause this short or is my coil bad?

 

[Rick.]

Re: 9.9 johnson cooling problem

Well I doubt it. If you see sparks then you have spark going to ground which is caused, usually by a break in the insulation. Check things over real well and try to determine exactly where the spark comes from and fix it. Pay special attention to your plug wires, Running your engine in the dark will allow you to see the spark (and hopefully the problem) much easier. Glad to hear you found the overheat problem. Rick.

 

[kbait]

Re: 9.9 johnson cooling problem

The coil in question may not be grounding correctly. Clean up the connection to ground from that coil and try rick's above.

Congrat's on the t-stat..

 

[matt88]

Re: 9.9 johnson cooling problem

Didnt get a chance to work on it today but that makes sense about the coil. Will definitely try cleaning the connection to the engine. I have been getting different answers from different marinas about which plugs to use in this motor. Was hoping someone might have a similar engine and could tell me what works best for them. One shop said le6c champion plugs another said ngk b6hs-10 another ul81c champion? I have been having trouble with my top cylinder fouling out at high rpm. Which is coincidentally the same cylinder as the sparking coil. I think a light bulb just flickered,lol. Maybe that coil is causing my problems but for arguments sake which is the best plug to use,thanks in advance.

 

[kbait]

Re: 9.9 johnson cooling problem

ul81c's are indicated, gapped at .030".