Over heating 79 Johnson 100 Hp

[brew happy]

I am still having an over heating problem, I have changed out the thermostats, and the impeller unit, but the right side cylinders still seem to be getting hot. It takes about 6-8 minutes before the alarm goes off, but still have trouble. Any ideas?

 

[HighTrim]

Re: Over heating 79 Johnson 100 Hp

What is the compression on all cylinders?

Have you inspected the water deflectors?

Does there seem to be a steady stream from the tell tale? (If one has been retrofitted)

What was the condition of the impeller housing? Was it changed? Grommet on top of housing not pinched when water line was inserted into it? Pinhole at top of housing clear? Was the water line flushed, backflushed when the lu was down?

Water intake area free of debris?

How have you measured the overheat? Do you have any actual numbers for the temp? Infrared thermometer?

 

[brew happy]

Re: Over heating 79 Johnson 100 Hp

What is the compression on all cylinders?

Have you inspected the water deflectors?

Does there seem to be a steady stream from the tell tale? (If one has been retrofitted)

What was the condition of the impeller housing? Was it changed? Grommet on top of housing not pinched when water line was inserted into it? Pinhole at top of housing clear? Was the water line flushed, backflushed when the lu was down?

Water intake area free of debris?

How have you measured the overheat? Do you have any actual numbers for the temp? Infrared thermometer?

I haven't check the compression as of late, Not even sure what a water deflector is, the pee stream is good, as soon as the motor is turned over there is a stream. The impeller looked good, hard as a mother to get the impeller off the drive shaft. Yes, all new impeller unit installed. I ran the motor with a hose attached to the water line, when the lu was off and yes the water intake is clear. I will try and get an infrared reading, but don't have one at hand. The thermostats that I put in were 133F instead of the normal 140F, that was all that was in stock.

Thanks

 

[HighTrim]

Re: Over heating 79 Johnson 100 Hp

The deflectors ensure that water flows correctly through the block. They need to be pulled and replaced if they are damaged, distorted, or deteriorated. If they are not set correctly, the flow of the cooling water will be disturbed.

Also, have you verified that it is in fact overheating

 

[brew happy]

Re: Over heating 79 Johnson 100 Hp

The right bank is for sure hotter that the left, too hot to hold your hand on, but the left you can hold your hand on no problem. Is the deflector plate inside the cooling jacket that the pee stream comes out of and did that motor not come with a pee outlet?

 

[Solittle]

Re: Over heating 79 Johnson 100 Hp

The deflectors are rubber hoses that are in the block to route the water flow. They are in the water passages around the cylinders and accessed when you take off the heads. Simple matter to replace them. Your shop manual (you have one???) will show you where.

 

[emdsapmgr]

Re: Over heating 79 Johnson 100 Hp

On the older V4 engines, the valve body in the thermostat housing has two pinholes, one for each side of the block. They permit heated water to get to the back of the thermostat, causing it to open. Not unusual for these pinholes to plug up with debris. Once they plug up, that side of the block will overheat.

 

[brew happy]

Re: Over heating 79 Johnson 100 Hp

Thanks for the info guys. Ok, so here are the numbers and info; after running the motor for 5 minutes, the heat buzzer started to go off again. The right side top cylinder was at 154, the bottom at 150, the left top was at 229 and bottom 206. So then I pulled the plugs and did the compression test, 3 out of 4 are at 130, the lower left at 125, so not bad at all. I put everything back together and decided to run the motor again, but brought the RPMs up to 2500 for about 5 minutes with nothing getting hot at all. Top right at 114, bottom 115, left top 112, bottom 124. Something seems a little weird, so I let the motor cool down more and ran her again for about 10 minutes with the same results. So I decided to wait a day and see if anything changed, so today I got home and started her up with nothing getting over 130, only time I reved her up so at start up for 20-30 seconds, then down to idle. Not sure if I had something blocking one of the water channels and now it is clear. We had some cold weather here for a few weeks, but wouldn't think that would have much to do with it, once the motor got some heat in it, everything should work just fine... So, I don't know if running the motor at higher RPM pushed a blockage out or what, but the motor is running good and cool now, I am still a little puzzled though.....

 

[Big Bubba]

Re: Over heating 79 Johnson 100 Hp

Brew Happy,
I ran my moter when it was a bit cold out and got the same thing. What caused this was the hose was so cold and stiff that I had to pull the hose completely out from the hose reel which is outside in the elements and had a kink in it. So make sure your hose is pulled out all the way in cold weather becuase they get really stiff and make sure your water is all the way up or full blast on and make sure your getting a good flow of water to the ear muffs and the motor before cranking her up. Hope this helps, Bob Let me know.

 

[brew happy]

Re: Over heating 79 Johnson 100 Hp

water flow wasn't the problem, I had good flow, but thanks.