1972 Johnson 65 hp heating up.

[Billy O]

My son bought this motor 2 years ago and it was running good, First the electric shift locked up while shrimping one night so the motor sat up for about a year before I finally repaired that. Motor never spit water out the 2 holes on the back like most older motors but ran great. Never over heated until I got it going again this past summer. Put in new thermostat,same problem. Took thermostat out and still heats up. I'm thinking water passages blocked or something. After all it did sit for a year with out flushing cause motor was locked in gear. Drop lower unit and stick hose up pipe from bottm and get good flow coming from thermostat holes. Any cheap ideas as to what to use to make sure passages are clear and what all needs to come off.

 

[tashasdaddy]

Re: 1972 Johnson 65 hp heating up.

water pump rebuild, bad impeller.

 

[F_R]

Re: 1972 Johnson 65 hp heating up.

Tell ya what---that particular motor had a problem. If it was even hinted at running hot, it warps the baffle plate in the exhaust cover on the side of the powerhead. When the plate is warped, it squirts water into the cylinders through the exhaust ports. That spells death to the powerhead. Just in case you wonder where old 65's go to die.

I guess you get the picture--if it has run hot, replacing the baffle plate and gaskets is mandatory. Not to mention fixing the water pump which is obvious.

Make sure the fat rubber seal where the lower unit bolts on is good. That could be why it doesn't squirt water. It has to fill up to the holes before it can blow out. The inner exhaust tube could be eaten up too.

 

[Billy O]

Re: 1972 Johnson 65 hp heating up.

Checked impeller, it has very little wear on the fingers and the key is in it so I know it is turning. It hasn't literally heated up on me. I just noticed it getting hot while running with hose hooked to it and shut it off. The big funny shaped seal in middle of lower unit was replaced when I redid the wires for electric shift.

 

[Texasmark]

Re: 1972 Johnson 65 hp heating up.

Don't forget a frozen shut thermostat as a possible source, also. I had one on a '75 Rude 70 hp.

Mark

 

[jay_merrill]

Re: 1972 Johnson 65 hp heating up.

I wouldn't worry too much about water not coming out of the backpressure relief holes in the back of the midsection. Mine shows very little water flow from them at any time. They are also not "thermostat holes," so what the t-stat is doing (or not) has nothing to do with whether or not you will see water coming out of them.

I would say that you have an obstruction somewhere in the cooling passages. Don't forget that the blockage could be before the waterpump, in the intake passages.



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[Billy O]

Re: 1972 Johnson 65 hp heating up.

Thanks Jay, I'll check below pump. I just don't believe impeller is bad. Very little wear on fingers and they are still flexible and fit in housing snug. Tried new thermostat and also ran with out thermostat. Might try taking t-stat cover off and crank motor with foot in a barrel to see if it is picking up water.

 

[jay_merrill]

Re: 1972 Johnson 65 hp heating up.

Your motor also has a pair of poppet valves right next to the t-stat. They are supposed to open when rpms rise to a level that will create enough water pressure, to overcome the spring loaded pressure on the valves.

I don't see any reason why these valves would create a blockage, but I've certainly been wrong before. I would make sure that they are in good condition and don't have a buildup of sludge around them.



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[F_R]

Re: 1972 Johnson 65 hp heating up.

Your motor also has a pair of poppet valves right next to the t-stat. They are supposed to open when rpms rise to a level that will create enough water pressure, to overcome the spring loaded pressure on the valves.

I don't see any reason why these valves would create a blockage, I've certainly been wrong before. I would make sure that they are in good condition and don't have a buildup of sludge around them.



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UM, "shrimping". It's a salt water motor. They are noted for corrosion building up around the rubber grommet around the poppet valve and squeezing the poppet so it doesn't open. However, I think we can dismiss that idea because he had it apart to replace the thermostat.

Personally, I think he should get it off those hose muffs and try it in the lake where it is supposed to run. How do we know there actually is a problem? Anyhoo, you can't check a water pump by running on muffs because you are supplying water under pressure. You could take the impeller clear out and water would go through.

 

[Texasmark]

Re: 1972 Johnson 65 hp heating up.

Just a comment. I may have misread the post but if I didn't. I had a '72 125 Johnny and it had 2 exhaust relief ports on the rear of the midsection just below the shroud that the motor cover sits on/connects to.

I used to waterski behind that boat and when we were up and running, like at skiing speeds, I would see a solid stream of casual water coming out of them. Otherwise it was just exhaust and a little "spit".

Since they are primarily above the water line engine exhaust gas relief ports, and they are connected to the midsection exhaust housing, carrying engine discharge water and all, it makes sense that this behavior is normal and to be expected.

Don't recall what happens with that engine on muffs......probably nothing but gas and spit.

Mark

 

[Billy O]

Re: 1972 Johnson 65 hp heating up.

I run it on muffs to flush it out. Has never pumped water out those relief ports for us. Didn't flush last time after river running because electric shift broke and it ran pretty fast in gear. Was taught to never run one in gear on a hose and couldn't keep enough water in the barrel.

 

[1946Zephyr]

Re: 1972 Johnson 65 hp heating up.

If a motor has been run in salt water and sat for a year without being flushed, the the chance of salt corrosion and blocked water passages is very likely. I have seen them plugged up to the point, where heads have to be removed and the powerhead, for a lot of scraping. Be prepared for a worst case scenario. The worst enemy to an aluminum engine, is salt water. The fact that yours heats up, with or without the thermostat tells me that you have a big blockage problem.

 

[jay_merrill]

Re: 1972 Johnson 65 hp heating up.

I have two '72 Johnson 65hp motors. One is on my boat and is run frequently and the other is one that I picked up for parts and/or use as is. I have only run the second motor a couple of times (needs carb rebuild) and that was on the stand with muffs. My "daily runner" shows essentially no water flow from the relief ports on the hose and the second motor shows a light, steady flow under the same condition. I don't know that much about the parts motor, but the one on my boat runs fine - no cooling problems and very reliable.

Texasmark makes a good point, however. I am usuallly out shooting photos in my boat alone, so I have no idea what is coming out of the relief ports at higher rpm.


PS: OK, Zephyr, you got me with the bug! I actually looked twice to see if I had a critter wlaking around on my monitor!



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