'72 johnson 65 HP overheating problems?

[Big Sky]

I have a 65ESL72S I took the boat out a few weeks ago and it got hot and quit on me. Just last night I replaced the water pump. I ran it this morning with muffs and it seemed to get really hot again just at idle and it didn't want to idle after it was brought back down.

I don't know how hot is too hot. I don't know what to do for cooling after I have replaced the water pump. Any help would be appreciated. Thanks --Big Sky

 

[mars bar]

Re: '72 johnson 65 HP overheating problems?

I have a 65ESL72S I took the boat out a few weeks ago and it got hot and quit on me. Just last night I replaced the water pump. I ran it this morning with muffs and it seemed to get really hot again just at idle and it didn't want to idle after it was brought back down.

I don't know how hot is too hot. I don't know what to do for cooling after I have replaced the water pump. Any help would be appreciated. Thanks --Big Sky

By replacing the waterpump do you mean the impeller? I have a 50 ESL and you should be able to put your hand on the L/U ccomfortably. I installed a tell tale noted in one of the search threads. Check for blockage at water intake.

 

[mars bar]

Re: '72 johnson 65 HP overheating problems?

Also try it in a barrel instead of the muffs. Good luck.

 

[F_R]

Re: '72 johnson 65 HP overheating problems?

Something you need to know about that motor. They cannot stand being run hot. At the very least, you must replace the head gasket and the exhaust cover gaskets (on the side of the powerhead. In addition, you will find that the inner exhaust plate will be warped from the heat and must be flattened or replaced. Even the sightest hint of overheating will warp that plate. If it leaks, it will destroy the powerhead from water ingestion.

Once you get the covers off, you can peer in and see if you scored the pistons. If so, it is all over for that motor.

And, needless to say, all this is in addition to getting that pump working 100%.

 

[Big Sky]

Re: '72 johnson 65 HP overheating problems?

By replacing the waterpump do you mean the impeller?

No I replaced the whole pump. But, as it sounds there are major repairs in my future. It maybe best to just get rid of it all together.

 

[Big Sky]

Re: '72 johnson 65 HP overheating problems?

I just did some research. It seems these motors have a thermostat. I wonder if that might be a/the problem. I will take that apart and see what I find.

 

[jay_merrill]

Re: '72 johnson 65 HP overheating problems?

Yes, your motor has a t-stat. It also has spring loaded valves that open, once the water pressure reaches a certain point.

It sound like to me, that you have an obstruction in the water passages somewhere.

 

[Big Sky]

Re: '72 johnson 65 HP overheating problems?

Well, I got a new t-stat and valves for the water passage today and put them in but it did not fix my problem. I also took the lower unit off again to recheck my work and look for a blockage. There was no blockage and the pump was just fine. So I dug into the exhaust plates per recommendations from F_R. There was water in two of the cylinders. I took out the spark plugs and turned the motor over and used penetrating oil to dispel the water. There doesn't seem to be too much scoring (after all it is a 72). I think I will get some gaskets look at the plates for warping and run her. I also thought about taking out the t-stat and valves so there is no restriction to the cooling water. I am cautiously hopeful I will have a motor for the rest of the season; until I can find a good motor to fit on my boat.

 

[Monte1961]

Re: '72 johnson 65 HP overheating problems?

Make sure the heads are flat before reinstall. Take flat piece of glass flat surface with some 220 grit sandpaper and move head back and forth a few times and then check for high spots. If you need to, do the procedure just enough to get high spots out. Post back results.

 

[Big Sky]

Re: '72 johnson 65 HP overheating problems?

So, I took a straight edge to the exhaust plate that bolts up against the block. My problem was not so much high spots but rather a warped (low) spot right where the exhaust comes out of the middle cylinder--I could see light under the straight edge. I am sure that is where it was leaking.

I took a hammer, brass punch, and a hard wood block and hit it back as close as possible to where it was. I can't see light under the straight edge any more and up against the block it looks as flush as the rest of the plate. I think I am just going to get gaskets and put it back together to see how she runs. I don't want to spend too much money on this motor. If it works great if not I will look for something else. (I only paid $420 for boat, motor and trailer)so, I do have some room to work with. I will post some pics to show what I found later. Off to get parts.

 

[ErikF]

Re: '72 johnson 65 HP overheating problems?

You probably already checked this, but when the engine is running you do have water coming out of the top?

 

[Big Sky]

Re: '72 johnson 65 HP overheating problems?

You probably already checked this, but when the engine is running you do have water coming out of the top?

ErikF, I did check that. What I think was happening is the exhaust was pressurizing the cooling system and overpowering the water pump so that water was not reaching the upper end of the motor. I am hoping the plate is flat enough that with new gaskets it will seal the exhaust leak.

 

[bernd64]

Re: '72 johnson 65 HP overheating problems?

if you take the T-stat out and the valves the water will not take the heat with them and the motor will over heat even faster.you have to have a restrition in the water flow to have time to colect the heat

 

[mars bar]

Re: '72 johnson 65 HP overheating problems?

If you plan to scrap the motor , I'll buy your shifter box off you.

 

[Big Sky]

Re: '72 johnson 65 HP overheating problems?

If you plan to scrap the motor , I'll buy your shifter box off you.

I'll keep that in mind. So far it is not on the chopping block yet.

 

[Big Sky]

Re: '72 johnson 65 HP overheating problems?

I am at a loss. I don't know what to do anymore. I replaced the whole water pump with a kit. I replaced the t-stat and valves. I replaced the exhaust manifold gaskets. In the process of doing all that I blew all the lines out with air and water. I didn't find any restrictions. I got it all back together and I am still not getting water to the top end of the motor.

Any suggestions?

I am running it with muffs and not in a tank but how much would that affect the pump?

I look forward to your replies.