1973 Mercruiser 165 hp running temp

[1stgenbird]

I took my newly acquired 1973 Silverline out on the lake yesterday for the first time. Overall it seemed to run ok. It still needs some tinkering as the only gauge that works is the temp gauge.
However, the operating temp was reading 190-200 degrees. As I am not familiar with stern drives, what is a normal operating temp? Is 190-200 too high?

Previous owner told me he replaced the impeller and housing the beginning of last season and didn't use the boat much after that.

What temp thermostat should be in this motor?

 

[Oshkosh1]

Re: 1973 Mercruiser 165 hp running temp

Should have a 140 t-stat.

190-200, if indeed that's an ACCURATE reading is about 30 degrees too high. Use an IR thermometer and read the temp at the sensor on the block(and various other locations to get an idea of temp...) to verify these readings. Your engine SHOULD be running anywhere between 160-175...give or take depending on throttle setting/water temp.

Don't know how "cautious" you are...however if it were me, I'd pull the drive and have a look myself. I'd replace it, then I KNOW when it was done. Also, it will give you a chance to grease the u-joints/splines and give the Gimbal bearing a feel.

Remember, with the impeller...only a few SECONDS running without water can do significant and irreversible damage.

 

[1stgenbird]

Re: 1973 Mercruiser 165 hp running temp

I';m going to pull the drive and take a look. I have to say that out of all the gauges; trim, oil press, amp, fuel, and tach, the temp is the only working gauge as it is a replacement one as the others are original.

I did open the engine cover while I was on the lake an it didn't smell or seem like it was running hot.

 

[glastronomic]

Re: 1973 Mercruiser 165 hp running temp

Lower leg impeller is one , but the waterpump and thermostat @ the front of the engine are also crucial in keeping it all nice and cool.
Thermoatat can easily rust out.
A full service on a motor like that when first purchased is highly recommended.