150 HPDI temp alarm

[wetcat]

Gday guys just came back from a great day out when i was flushing the motors through the temperature gauge went off its face after about five mins of flushing. I noticed the prop wasn't spining (just in netrual) the othere one was and the tell tale wasn't spirting no where near as much water as the other one just a slight squirt. Could this be the impellar has craped itself the motors are due for there 100 hour service in 10 hours can ya change tthe impellar by yourself or should i let the boat shop do it thanks cheers Mick H

[Ken]

Mick,
There are several possible reasons why your motor overheated when trying to flush.
(1)Low water pressure from the garden hose is a possibility, or, if using earmuffs, improper placement of the "ears".
(2)With only 90 hrs on that motor, the impeller should not be worn out, but could still be defective.
(3)The pressure relief valve, aka pressure control valve, poppit valve, could be stuck open and allowing cooling water to pre-maturely dump out the relief holes.
(4)The intake to the water pump could be clogged up - inspect the intake screen.
(5)The cooling water jackets could be clogged, but not likely at 90 hrs, unless you have been running a lot in shallow water.
(6)The thermostats, one in each head assy, could be stuck closed or not opening all the way to allow enough cooling water to enter the heads.

If you want to tackle a water pump repair yourself, best to get a Yamaha service manual to guide you along. Normally, on average, owners do a water pump repair every two years. Best to watch someone familiar with the task do that first one.

For the future, you might want to consider adding a water pressure gauge to each of your motors.
The wp gauge is the best indicator of water pump performance. Should have around 5 psi at idle, and increasing from there up to around 20 psi at 3000 rpm and beyond.
Good luck [img]smile.gif[/img] ,
Ken K

[wetcat]

Hey Ken thanks for the reply man i thought myself that the impellars should have lasted a bit longer, I'm gonna take your advice and take her down to the boat shop and get some one to look at her. The reson we dont think its the water pressure is that we ve been flushing it the same way for the last two months and nothing has come up before, by the way i'm not using muff im using the water intake nipple connected straight to the hose are the muffs better cause they deliver more water to the motor?? Cheers Mick H

[Ken]

Mick,
That hose connection should be adequate, but if I had one on my outboard (which I don't with my little C115) I would still use the earmuffs - that way I know I am getting fresh water thru the water pump and tube.
When flushing, let the motor warm up enough for the thermostats to open, typically five minutes minimum. That way you know water is flowing thru the head water jackets.
Good luck [img]smile.gif[/img] ,
Ken K