Motor: Merc 135 V-6, 1991. Ser. No. 0D007523<br /><br />I've had my boat back out on the lake a couple of times since I destroyed the impeller due to ignorance one hot day in August. I replaced the impeller and ended up having to replace a switchbox too, which I think failed due to overheating. The motor runs fine now, but I think I am seeing abnormal temperature readings. It's hard to be sure though, because I hadn't had the boat that long before I broke it, so I am not positive that it always ran at 145 degrees before.<br /><br />Anyway, I have been fiddling with it. One day I was about to replace the thermostats, so I left the thermostat housings off the motor and ran it to see what the water flow was like. Water gushed out like I would have expected. I put the new thermostats in the motor and ran it, and I still am seeing temps of about 185 degrees (but it does seem to fall to 145 occasionally). By the way, I tested my overtemp horn and it works, and I get no overtemp alarm during any of this.<br /><br />Today I dropped the Lower Unit again to see if there was anything visibly wrong, and I saw nothing. But while I had the Lower off, I hooked up a garden hose to the water intake pipe and ran the motor, and I still saw the higher-than-normal temps. So my water pump is off the hook, right?<br /><br />I took the hose off at the starboard thermostat and blew through it. No constriction there. I undid the hose where the poppet outflow goes to the top of the powerhead. I blew air back down the hose to the poppet, and also into the fitting on top of the powerhead and there was no apparent restriction there either.<br /><br />I've looked at a lot of threads here where folks are advised that they should be able to hold their hand on one of the cylinder heads for five seconds, and the telltale stream is supposed to be cool (really??). I find neither to be the case with my motor. I can put my hand on the heads for about three seconds, and the telltale stream is hot---hot enough to produce a little visible steam vapor. I can keep my hand in the telltale stream about five or six seconds.<br /><br />So, I am thinking I have eliminated the water pump itself by running directly off the garden hose. The pump seems to deliver a good supply of water to the thermostats, which are new. And the outlet from the thermostats does not seem to be clogged. The one thing I am not certain at all about is the poppet. How does this work, and why? Where does its flow come from, and where does it go? And WHY?<br /><br />I am beginning to think that my temp sending unit may have been damaged during the overheat episode. Is this possible?<br /><br />Thanks in advance!<br /><br />-dd-
