Water Cooling issues

[amk54055]

I have a 2006 Yamaha 60 HP T60TLRD on a pontoon boat. 2 years ago it quit peeing out of the tale tale hole. I figured out I could drive it over so many RPM's and it would work. If I were to go below 2000 RPM's or so, the stream would stop and eventually the alarm would go off. So, over 2000 RPM, normal operation, less than 2000 RPM No stream.[FONT=&quot] [/FONT]
I replaced the entire water pump system and it didn't help so I continued to drive it just over 2000ish RPMs. This year I'm ready to fix it before I screw up and burn the motor up. Today I replaced the thermostat and that didn't help. While the thermostat was out, I was able to take the water hose and spray water into the place the thermostat goes and it sent a very good stream out of the tale tale. I took the thermostat out again and the area was dry. I don't seem to be getting water to the thermostat. Does that send me back to the water pump? Could the water pump be ok and something between the water pump and the thermostat be a problem? I could have botched the water pump installation but assuming I did it correctly, am I missing something? Thanks for all your help.

 

[tommarvin]

I would drop the lower unit and check the impeller, does it look ok, is the keyway in the driveshaft holding the impeller in place and can't spin on the drive shaft,
The water indicator stream should stream water in 30 seconds after start up or something's wrong. You have to orient the impeller fins for a clockwise driveshaft looking down at it. You-tube has great videos on impeller changes.
That was smart to put the hose in the stat hole to check for blockages.
If you would bet your life the impeller is ok, then you have to remove and check the cooling/exhaust jacket for blockages in the water passages this is in between the water pump and stat the last thing to check.. This usually happens on salt water motors when people don't flush there motors.

 

[Scott Danforth]

well, something started being amiss two years ago. if it was a blockage, it may now be hardened into the equivalent of concrete requiring you to pull the water jacket covers off the power head and chisel crud out.

is this a fresh water boat or a salt water boat?

lets start with the basics. think about the flow of water, follow it with your head thru the motor, and you will find the problem

in general, water comes from the intake grids to the water pump and impeller. from there, it travels up a tube to the bottom of the power head. inside the power head, it goes thru the water passages filling the water jacket of the block up, then to the exhaust covers then to the thermostat housing, where it then exits the motor via the tell tale hole and into the exhaust stream.

pull the lower back off, run water up the tube, if you do not get water comming out the thermostat housing, you have a blockage.