1992 Evinrude 4hp 2-Stroke - Overheating Problem

[brendantownsend]

Following a full service, I took my 1992 4hp 2-cyl Evinrude o/b out today and ran the motor at near-WOT for about twenty minutes until I eventually noticed steam emerging from the pee hole and was clearly overheating. I pulled over to the bank, tilted up the motor, inspected the intake but couldn't see "much" in the way of weeds or debris. I then gave the block about 10-15 minutes to cool down a bit, dropped it back in the water, and it started straight up again with a good flow of cooling water as before.<br /><br />I then ran at a very modest throttle (just above idle) for about ten minutes until I noticed the cooling water gradually reducing and stopping, so once again I pulled over to the bank, tilted up the motor, dug around the intake blind with my finger (I was still in the boat so couldn't see it directly) and a single large-ish leaf dropped away.<br /><br />I then dropped it back into the water (not more than about a minute later from stopping), started it up, and immediately a good flow of coolant water as before. Ran the motor for a further ten minutes at a modest pace again but this time no apparent reduction in water flow.<br /><br />This leads me to ask just how usual is it for the intake to get repeatedly blocked in moderately "weedy" water (inland river) and would it be reasonable to assume that this was the cause?<br /><br />Alternatively, is there a thermostat fitted to this particular model and could this possibly be the cause (sticking, etc)?<br /><br />Finally, is it likely that the impeller was damaged the first time it overheated?<br /><br />With thanks in advance,