1975 4hp running hot

I recently dragged my grandfather's 1975 Evinrude 4 hp out of the attic. I put new fuel in tank, changed out fuel line, replaced the gear oil and the little dude runs like a champ!

My question is it seems like it is running too hot. When I shoot a laser thermometer at the cylinder head by the spark plugs it registers around 240 degrees and around 200 degrees on the side of the cylinder.

I am fairly confident the water pump and impeller are working because I get drops of water spitting out the 8 small holes on the exhaust housing (above the water line) and I also get some water coming out of the exhaust outlet above the propeller (I have the weedless model #4506).

Any thoughts here?

I am new to this and just want to see granddad's motor running and kept in great condition like he did. Thanks!!

Re: 1975 4hp running hot

Welcome to iboats.
Suggest you give the water pump a service and at least change out the impeller. Rubber will deteriorate with age. If there are any "bits" of the old impeller missing they are most likely somewhere in the cooling system. If so give it a back flush. Then check again. Small investment to make to make sure all is well.
Good Luck.

Re: 1975 4hp running hot

Will do...thanks for the advice. Does servicing the water pump just consist of replacing the impeller or is there more?

I think the cooling system is clear of blockage. I put compressed air through the tube coming out of the water pump and i felt air exiting the exhaust area.

Thanks again.

Re: 1975 4hp running hot

Many times the reason it doesn't pump in a barrel is the water level simply isn't high enough. Make certain your water pump is way below the water level not unlike it will be on your boat. At this point I would agree a new impeller is a good idea anyway. Your temperature readings are way too hot. If you continue to let it get that hot you will have more expensive problems ahead. I have a 71 and worked on a 73 and neither had thermostats so normal temp. to look for is 140 F. but with no stat they should run even cooler. Great little motors and glad to hear your getting this one out of storage. Best of luck. Rick.