cooling an old motor

I have an old ’53 Evinrude on my boat that runs great. How can I tell if it’s cooling properly and the impeller is not shot. The water comes out with the exhaust (above water), not like the stream of newer motors but more like a spray. At higher RPM’s it “looks” like it’s cooling, but at lower RPM’s it doesn’t. I don’t know if the impeller is easily accesible to physically check it.
Any imput would be greatly appreciated.

I had a ’65 Chrysler that was the same way. it barely spit anything out at idle. Actually, that is when it should be spitting out more. When you are running, your thermostat should regulate the h20 temp to around 140 degrees. when you are idling, your thermostat is going to open all the way (depending on the temp of the h20 of course) and the spray will likely be hotter. If you don’t know when the impeller or thermostat were replaced, replace the impeller (they are easy and cheap to replace) and take out the thermostat, check the temp on it (usually stamped), and heat a pan of water to that temp or slightly above, drop the thermostat in there, and see if it opens. If it does, you are good to go, if not, replace (don’t forget the gasket as well)

oh, test the thermostat first, so you don’t have to make two trips to the store.

here is a good site for cross-reference for parts:
http://www.theshadconnection.com
or for troubleshooting:
http://www.brokeboats.com/

Hope it helps!

One good way to check to see if your old motor has overheated in the past is to check the paint on the motor block. If the paint is all cracked then the motor has overheated sometime in the past. A marine mechanic I know pointed that out to me several years ago.

You didn’t say what size your old motor is but if it is from the 50’s it is probably under 40 hp. I used to own an 18 hp Evinrude from the 1950’s. I had a P-tube installed for very little money to ease my mind whether or not the water pump was working. I did change the water pump on it once myself. I had to take the entire lower unit off to change it but it only took about an hour or so. I did have difficulty getting the linkage hooked up again for the transmission (forward, neutral, reverse) as the old brass couplers needed to be replaced.

I would say that if your motor is pumping water out that the motor is cooling. It is difficult to tell on the older motors without the P-tubes. You may want to invest in the suction-cup type device that you hook up to your garden hose. It fits over your water intakes so that you can run your motor without having to put your boat in the water. They cost less than $5. Then you will be able to tell if you are getting good water flow.

Eyehunter

One way you can do this too is get a garbadge can and put it under the motor and fill it with water. Leave it in neutral and start it. After its run for about 10 minutes the block next too the head should be fairly warm to the touch but not too hot. If you feel it getting warm enough that you can’t hold your hand on it its the impeller. You can take it to your local boatramp on a day when the ramps not busy and try it there too making sure the intake and pump is below the water line. These pumps aren’t self priming so the pump has to be under the water too. While running it check for water flow because the water should come out the exhaust port quite a bit, not here and there spurts but a good amount of positive flow. If you have to drop the lower unit take the bolts out of the lower unit that holds it too the midsection, i think theres three bolts, one on the underside of the lower unit and two on top going down into the lower unit. Theres an inspection cover on the side of the mid section about 3 inches long that has two rods in it with a coupler connecting them. Theres two 3/8ths ” or 7/16ths” bolts that hold the rods in the coupler, undo both bolts and take them both out. Inorder for the rod to drop down you might have to take a screwdriver and open up the coupler so the rod drops down. After the lower unit is off theres 3 or 4 3’8″ths bolts that hold the upper water impeller housing to the lower housing. Take these out and pull the upper housing up the drive shaft and off. Then pull the impeller up the shaft but be careful not to drop the key thats in the keyway that keeps it turning with the drive shaft. Put the new impeller on the shaft, put the key in the keyway and slide the impeller over the key. Reassemble the way you took it apart. Its a little tricky to slide the rod in the coupler and keep the lower unit up at the same time but you can do it after a few tries. This is pretty well step by step, this is how i change mine and Hope this helps