1970 45 hp overheating

[59 evinrude]

I finally got my 70' 45 hp Chrysler running good. But, I did notice something when I was out today. When I am running about half throttle, the temp is about 145 degrees. When I am running it at full throttle, it runs about 180 degrees. The gauge goes into the red, but not pegging at 200 degrees. When i back it back down to half throttle the temp comes back down. I am getting a good coarse spray out of the back. Is this normal, I can see it running a little hotter when at full throttle, but I don't know if 180 is too high.

 

[fucawi]

Re: 1970 45 hp overheating

180 F ( about 88C) is not excessive but I would have expected a little less ....Test the thermostat by suspending in an electric kettle and checking if it opens as the temp rises ..best if you have a thremometer in there ...

 

[bentle]

Re: 1970 45 hp overheating

Just a couple questions for ya. Did the temp gage come manufactured with the boat and motor,
and have you replaced the impeller recently?

 

[59 evinrude]

Re: 1970 45 hp overheating

i think the gauge did come with the boat. that could be part of the problem, its a 40 year old gauge that has been sitting out in the elements. i am trying to find a thermostat right now. i cant seem to find one. the water pump was replaced a few years ago by the previous owner. he didnt use the boat much after that.

 

[bentle]

Re: 1970 45 hp overheating

Try boats.net or another is seaway.com, so was there a thermostat in there to begin with?

 

[59 evinrude]

Re: 1970 45 hp overheating

there was. it is not froze up or anything. it actually looks really clean. i didnt test it, i figure since its out, i might as well replace it.

 

[vt750dc]

Re: 1970 45 hp overheating

im having the same problem with my 74 model 75 hp; replaced the water pump, removed the power head and replaced the o ring on the water tube today, replaced the thermostat, temp. sensor, and replaced exhaust side cover gaskets and cleaned all water ports but still have the same problems you have; so im just gonna swap complete engine and see what happens; lucky i had a spare. maybe its ok.

 

[tater76]

Re: 1970 45 hp overheating

I would definitely replace the impeller, I do this every spring upon waking any of my engines. It is relatively cheap insurance versus overheating and having to rebuild. As for temp, I have never relied on guages in any boat I have ever owned, because as you said these things tend to sit out in the elements, and things break. If you can install a telltale that would put your mind at ease. As long as my Chrysler and Force OB's are spraying water I don't worry about high temperatures.

 

[bentle]

Re: 1970 45 hp overheating

Good water flow is always good. Can you pull the sensor at the motor that sends temp to the gage. Im thinking it may have some junk built up on it and could be sending a bad reading or even defective. You should be able to touch around spark plug area on the head and the exhaust plate and it should be warm to the touch but not like you could fry an egg on the motor. Be careful though and don't get burned. Touch it very briefly. The gage in the dash could very well be bad as well if it is 40 years old.