Logo
FULL SITE MENU

Cooling issues with a 1979 Johnson 9.9hp model 10sel79B

R

rhoyer10

New member
Hello
I am new to this forum and this is my first post.
I have a 1979 9.9 hp Johnson (10SEL79B) that is overheating. Very little water is coming out from the pee tube.
Here is what I have done so far
Checked for a clogged hose. it was ok. Pulled the lower unit and replaced the water pump with an OEM kit. Pulled thermostat cover and replaced a very deteriorated thermostat.
The issue is that it is very hard to blow through the water tube going up to The powerhead. I blow compressed air in reverse and it is a struggle to get air through.
I ran the lower unit in a tank and the pump is pushing water out of the output hole.
I reassembled the unit and ran the motor in a 32 gallon barrel making sure pump was well submerged. same problem very little water out of pee tube and engine starts to overheat.
Help would be much appreciated if I could be steered in the right direction.
I am thinking a blockage due to the deteriorated thermostat.
Thanks in advance for your help.
 
Blowing air from the block down usually will not put air through the tube. I would pull the powerhead because there is a small rubber grommet at the base of the powerhead for the water tube. These can go bad over time plug the tube.
 
I pulled the lower unit on a 76 yesterday that had symptoms like yours.
With only a garden hose and compressed air was able to resolve the problem.
 
flyingscott said:
I would pull the powerhead because there is a small rubber grommet at the base of the powerhead for the water tube. These can go bad over time plug the tube.
Click to expand...
This is your problem. I chased the exact sample problem on my '79 9.9 just like you did...water pump, thermostat, etc and still had flow issues. An old member on here, Joe Reeves pointed me to the water tube grommet. Sure enough, when I pulled my powerhead the grommet was disformed and had folded over on itself.

See this diagram: http://www.marineengine.com/parts/j...&manufacturer=Johnson&section=Exhaust+Housing

The grommet in question is #39 on the diagram, part number 0324045. You'll also need a new base gasket, part number 0325721.

KJ
 
Agree. Sometimes the grommet only partially folds up....then debris collects underneath it....weed chunks, etc. Sometimes by blowing backward from the power head down you can eliminate this debris and PARTIALLY open the tube but that is not a permanent fix. THE GROMMET MAY CONTINUE TO DETERIORATE UNTIL IT CLOSES THE TUBE ON ITS OWN. Then you can burn up your motor. I usually fabricate my own grommets here.
 
You will then remove the 4 bolts on exhaust tuner. It will be stuck pretty good. Can you post a picture to show what you find? Remember to reduce file size to 1000k or less. Thanks. Let's keep this the very best marine forum available.
 
I tried that both ways and no help. Apparently the rubber grommet has finally given up and is blocking the water tube
Thank you for your suggestion.
 
Actually, I had the thermostat cover and thermostat removed when I tried it the first time with no results. I am about to remove the power head today so we'll see what gives.
Thanks for the information
 
rhoyer10 said:
Power unit pulled. Grommet was deteriorated and closed off about 80%
Thanks for your help
Click to expand...
Glad you found the culprit. I fixed mine about 5 or 6 years ago and it's had a good steady water stream since. Once you install the new grommet you should be in good shape.

KJ
 
Parts are on order and will be here Saturday. Motor is in surprisingly good shape for being 42 years old.
I should have it back together by early next week.
Thanks for your help and input.
Bob
 
Back
Top