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2001 150HP 2-stroke (150TXRZ) Overheats at idle

bulldurham

New member
Sorry for the long opening, but I've done quite a bit
already, and I'm really confused.

Ran motor all last season with no
issues. The motor has never been in salt water. The motor was not used for about
2 months before I winterized it. When I winterized in the fall, just as I was
ready to shut it down, the overheat siren came on. Hoping it was a fluke, I put
it away anyway. I started it again on earmuffs yesterday. The overheat problem
wasn't a fluke.

Here's what I've checked so far:

1) Motor always
pees good.

2) Checked thermostats in pan of water. They both open at
approx 122 degrees like they are supposed to.

3) Pulled lower unit and
checked impeller. Everything looks fine.

4) I drilled a hole through one
of my kids bouncy balls and stuck that on the end of my air hose. Stuck the
ball/air hose on one thermostat opening, covered the other with the palm of my
hand, and had my son make sure there was good air flow coming out the tube in
the lower unit. He said yes, so it seems there was no obstruction there.
Repeated the test by holding air hose on other thermostat opening and still good
air flow.

5) Started motor on earmuffs for about a minute with no
thermostats and no thermostat covers, just to see if water was filling the
block. No water made it to the top of the motor.

6) Pulled Poppet/PRV
pressure relief valve. It seemed like it may have possibly been stuck in the
closed position. However, from what I've been reading, it should be closed at
low RPM anyway. Cleaned it up a little and don't see any reason it wouldn't be
working properly now.

7) Hooked a hose up to the hose connector on the
port side of the motor and tried flushing the motor. I had the poppet valve out,
and both thermostats out. Water did come into the opening where the poppet valve
goes, but didn't seem to have much pressure even though the hose was on full
force. I stuck my finger in the PRV hole to plug it, still no water to the top
of the motor on either side.

I'm really confused.

I think the
water flow is supposed to:
1) Come in water inlets in lower unit to feed
water pump
2) Water pump pushes water up the tube to the bottom of the motor
where the poppet valve is.
3) If there's too much pressure, some is released
from the poppet valve.
4) Water is pushed into water jackets surrounding the
cylinders to the top of the motor.
5) Thermostats hold water and keep it from
flowing out of the water jackets into the heads until proper temp is
reached.
6) Thermostats open and allow water to flow through the heads and
back down through the bottom of the motor into the lower unit.

I'm pretty
sure water is supposed to get mixed in with the exhaust, but there seems to be
very little coming out the center of the prop and none coming out of the ports
in the upper lower unit.

Based on what I think I know, I would think the
water pump isn't generating enough pressure or there is a blockage between the
water pump and the pressure relief valve location. However, if that were the
case, I'd think I'd get water to the top of the motor when I hooked it up to the
hose connection on the port side of the motor.

Please help!
 
Ran some more tests this morning and even though the water pump visually looked OK, it must be bad.

Here's what I did:

1) Pulled off lower unit.
2) Plugged the tube going from the water pump up to power head (electrical tape across the end).
3) Put PRV back in. Left both thermostats out and caps off.
4) Hooked up to hose connection turned on water (low pressure) and plugged the pee hole with my finger.

This left the water no place to go but into the water jackets and out the holes where the thermostats go. Sure enough, that's what happened. The port side thermostat hole is slightly lower than the starboard side. After the water started out the port side, I put the stat back in and made sure it came out the starboard side stat hole.

When I removed the tape, water that had collected in the tube came rushing out.

Just to double check, I used that rubber ball on the end of the hose and at the bottom of the tube. Plugged pee hole and water eventually came out the stat hole again.

Great news for me! No engine teardown trying to find a restriction that isn't there.

Water pump must be creating just enough pressure to get water up the tube to the bottom of the motor where the PRV and pee indicators are, but not enough to fill the block.

I'm off to buy and impeller.
 
Get a whole pump kit with the housing. Does your engine have the impeller lock with the two washers and spring washer on the input shaft? If it is supposed to and they are missing make sure you install them.

Do not use the rectangular muffs on your engine. The cheap round ones work the best. A drum of water is the best.
 
That was the problem. Replaced impeller and it runs fine now. Really can't believe it. It was only a year old. Had a little bend in the blades, but still seemed to have plenty of flex in them and absolutely no visible wear.

Thanks for the reply Chris. I actually replaced the whole pump a year ago. Yes, I had everything together correctly (
impeller lock with the two washers and spring washer on the input shaft? . . . and I use . . the cheap round ones.
 
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