1999 Model Yamaha 90hp 2 stroke 3 cylinder

[bronco74]

While recently running the outboard on the hose hook up, I noticed that the water pump stream coming out the side of the motor was flowing, but not very strong. After idling for 10 minutes giving it gas every so often, I also noticed that the two back exhaust/water ports never released water. The stream of water began to warm up and the lower unit started to get mildly hot. At this point I killed the motor. I purchased a new impeller kit from yamaha, and still have not installed. I am wondering if the problem could be a broken thermostat, preventing the outflow from the two back ports. The local yamaha dealer said that the impeller probably needed changing, but never mentioned the possibility of a broken thermostat, which would circulate water through the engine block. Could this be a possibility? Thanks in advance.

[99yam40]

I believe you are talking about the idle exhaust relief ports, they are there to give the exhaust gases some place to go when lower unit is in water causing back pressure on the exhaust. On the hose the gases exit the prop without the back pressure.

should have a lite spray of water out of the relief ports when ideling in the water but not sure if it will come out on the hose. My c40TLRX does not have any water coming out of those ports on the hose or the water and I worried about it for the 1st year, but do not even think about it anymore.

If you have not changed the water pump or thermostat in a few years do it, but you could pull and test stat and reinstall if it is in good shape and functioning like the specs call for

[robert graham]

Same exact motor as mine. Sounds like you may not have a problem if it's running fine and not overheating...just drop the lower unit and replace your water pump. You can replace the thermostat also, if it's not cooling properly, or just as preventive maintenance. I've replaced my water pump twice since the motor was new in 1999, but I'm mostly in fresh water. I've never replaced my thermostat, but I plan to do it, preferably Before it fails! Good Luck!

[bronco74]

Thanks, really appreciate your input