[dmiller40]

I just bought this motor recently. It's a 1972 Evinrude 6HP. I replaced the water pump impeller (the old one was not broken, just old), and rebuilt the carburator. It runs smooth and pumps plenty of water, but the first time I ran it (after replacing the impeller) I noticed that the engine was not heating-up. I removed the thermostat cover and discovered that the thermostat was stuck open. I then replaced the thermostat with a new one. With the new thermostat installed, the top of the block, next to the cylinder head, gets very hot. The cylinder head does not get hot, only warm, and the block around the lower cylinder is only warm. I am concerned about the temperature around the upper cylinder. I can not hold my finger on the top of the block for more than a second.

I removed the new thermostat and ran it that way (no thermosat) and again, the block stays cool.

Any suggestions? could I have a cooling blockage in the block, or is this normal? I don't want to damage the engine.

[F_R]

Does it sizzle water if you sprinkle some on it? That's too Hot. (Poor-man's temp gauge). Water flows through the powerhead in two paths. One path may be clogged. It's been too long for me to remember where the likely restriction may be.

[dmiller40]

No, it doesn't sizzle water, just too hot to touch.

[dmiller40]

OK, did a little more investigating.I think I might have a partial blockage in the upper cylinder cooling passageway. Here's what Iv'e done so far:

I removed the thermostat cover and thermostat, then started the engine and ran it at low speed for a short time with the thermostat cover removed to observe the water flowing into the thermostat housing. There are two holes leading into the thermostat chamber. I'm assuming that each hole is the cooling passage for one of the cylinders. Here is what I observed:

• The lower hole in the thermostat chamber was spraying a stream of water.
• I couldn't tell if any water was spraying from the upper hole, because of all of the water coming from the lower hole.
• When I plugged the lower hole with my finger, the upper hole began spraying water.

Does this sound normal? If I have a partial blockage in the block, how can I clean it out? Any recommendations?