overheating 9.9 rude

[okam]

I have a 1975 9.9 evinrude, install new water pump assembly. started it up could see small amount of water discharge till it warmed up and overheated. Could this be a stuck t-stat or a water passage problem. I pulled the lower unit again and checked where the tube slips in the grommet, and it looked good restarted same problem. Could a head gasket do this? It has 70 psi both cyl cold. Thanks for any insight!

 

[Joe Reeves]

Re: overheating 9.9 rude

A failing head gasket or stuck thermostat could create a overheating problem BUT that problem is usually caused as follows.

The most likely and most common problem is that the upper grommet that the water tube fits into (under the powerhead) has swelled and is creating a water restriction.

It will be necessary to remove both the lower unit and powerhead in order to replace the grommet.

 

[okam]

Re: overheating 9.9 rude

Thanks Joe Reeves, I was afraid of that. Is the compression for that high or low? I have a 140 looper that Those numbers would be low.

 

[Joe Reeves]

Re: overheating 9.9 rude

I wouldn't be concerned with the compression you have there. On those small hp models, compression depends on the rate of speed the engine is turning over, whether the cylinder is dry or lubricated, and the psi can vary from gauge to gauge.

If the engine runs okay, just make sure the head bolts are tight.