engine over heating 1954 7.5 hp

1954 Evinrude 7.5 hp rebuilt, pistons, rings, crankshaft, coils etc. Replaced impeller. Converted to long shaft. Runs, but overheats quickly. Removed powerhead and placed drill on drive shaft. 8 to 10 inches of water comes out of water tube so impeller is working. Initially, when engine is started water comes out of cylinder head water exhaust but gradually just spits out very hot water. I have also removed the water flush screw but havent flushed yet. Would this help. Any other suggestions?

Re: engine over heating

Not real sure but I would be looking for a themostat you would be surprized sometimes how small thay make them and where thay put them the only otherthing right now I can think of is if you put a gasket in wrong that would be blocking the water flow.

Re: engine over heating

That engine does not have a thermostat. Double check your impeller installation..... a scored water pump plate or badly pitted impeller housing could kick up a air pocket.

Seal the impeller plate to the lower unit.... and the impeller housing to the plate with "Bombardier 3M Product #847" sealer, available at any dealership (or at least it should be). The lack of this sealer could (and usually does) allow the water pump to draw air.

When running, whether in a barrel or on a boat, at a standstill, the water must be a couple inches above the water pump location. When on a boat, the cavitation plate which is just above the propeller must be approximately 3/4" below the bottom of the boat, no lower than 1"..... and absolutely not above the bottom of the boat.

If the above is as it should be, I would suspect a slight leakage between the head gasket and the water passage area. If so, inspect the sealing surfaces of the head and block and correct if needed. Tighten the head bolts in the following sequence.

9....10
5.....6
1.....2
4.....3
8.....7

Joe

Those are great ideas. I did not use any sealant when I installed the impeller. I removed the powerhead, disassembled the water pump to apply the sealant. I note a thick oily, grease build up on the waterpump housing and throughout the unit. Could the seal the driveshaft goes through directed under the impeller plate cause gear oil to leak into the water pump and cause problems?