1972 OMC overheats

[slriverrat]

I have replaced the water impeller in the lower unit, the hose that feeds the thermostat cover, the thermostat (160 deg) however the motor still overheats on normal fresh water. When house water is hooked to the flusing port or directly to the the thermostat, the temp stays at 160 deg. While the house water was hooked directly to the themostat cover I measured the flow from the lower unit and got about 1.25 gal per min. without much pressure.
The engine is the 4 cyl inline 165hp and is mounted in a 1972, 20 ft. Thompson.

Any ideas?

 

[rabeck5792]

Re: 1972 OMC overheats

could be the seals in the swivel bearing housing sucking exhaust or pump hsg not sealed well.

 

[havasuboatman]

Re: 1972 OMC overheats

When you replaced the impeller, did you get all of the old impeller and any pieces out of the system?
did you replace the impeller housing as well as the impeller?
Are you sure you got the water tube seated correctly when you put the drive back together?
I'm curious, have you been running this motor without water hooked up to the impeller?

 

[slriverrat]

Re: 1972 OMC overheats

I now have the boat out of the water and it has been suggested that I try to get some more grease into the swivel bearing. I will try that now that the boat is out of the water.

 

[slriverrat]

Re: 1972 OMC overheats

I had a pro replace the impeller so I can not be sure that all of the parts of the old impeller were removed. When the boat is out ov the water and i need to run the engine water is introduced from the house garden house via the flush out adapter on the port side of the out drive.

 

[slriverrat]

Re: 1972 OMC overheats

When you replaced the impeller, did you get all of the old impeller and any pieces out of the system?
did you replace the impeller housing as well as the impeller?
Are you sure you got the water tube seated correctly when you put the drive back together?
I'm curious, have you been running this motor without water hooked up to the impeller?

Well the boat was taken out of the water. The bearing was given a good dose of grease. The inspection plates were removed and all of the chamber rinsed out. The water inlet plate was removed, rinsed out, that area, installed a new bronze screen. Then everything was put back togeather and with the lower unit sitting in a tank of fresh flowing water I gave her a try. I ran it for 10 min at 1200 rpm and the temp never exceeded 160. Thanks for all of the advice. On the river water trials tommorrow.

 

[rs2k]

Re: 1972 OMC overheats

The drive needs to be immersed up to the height of the water impeller or it will not flow water when sitting in a tank. This is difficult to do on a stringer drive. The whole low end needs to be more than submersed.

 

[slriverrat]

Re: 1972 OMC overheats

Follow up questions. Are the seals metal to metal or some kind of soft material that will have to be replaced at some point? Can the seals be over greased? Is once a summer before, launching often enough to re-grease?

 

[rs2k]

Re: 1972 OMC overheats

The seals are metal to metal (outside of seal to housing) but have a soft rubber end with a spring around it and should be replaced at LEAST every 5 years from what I've read. You also have o-rings and gaskets. They look like wheel bearing seals. I just went through and replaced all the seals on my two mechanical shift drives. You NEED to get a service manual if you wish to do this yourself.

I used exhaust couplers as seal installers and permatex around the seals. I've also read that you can use lock-tite, but I don't know how difficult if would be to remove the seals after that. Make sure you do a pressure test, all three gear cases should be able to hold 10 PSI of air overnight and 7 HG of vacuum overnight. After replacing the seals on one of the low end units, I found it did not hold pressure. I used soapy water to find that it was leaking from the shift housing around an o-ring.

I grease everything about every 25 hours. I believe you can go up to 50 hours or once every oil change. Greasing is pretty easy to do.

 

[rs2k]

Re: 1972 OMC overheats

Here's a picture of an upper gearcase seal kit:

http://www.sterndrive.info/sitebuil...651-OMC-upper-gearcase-1968-1972-seal-kit.jpg

 

[Daviet]

Re: 1972 OMC overheats

Does this unit have the electric shift lower unit, not sure when the change over was.

 

[slriverrat]

Re: 1972 OMC overheats

Yes it has an electric shift in the lower unit.

 

[WizeOne]

Re: 1972 OMC overheats

Yes it has an electric shift in the lower unit.

Makes not much difference as far as the impeller is concerned. Electric shift and mechanical shift upper housings are virtually identical.