1990 ProV 150 Overheating

[zenoahphobic]

Prima faces sounds like water pump - they are fickle
You said burning on previous pump housing; this raises the possibility that a previous impeller may have also broke leaving a small piece stuck in a passage somewhere. I hope not because if the case you may again have to pull it apart.

[MNY4m4h4]

I'll give this a go and post the results

[erniefish]

No, you will be fine,the water hose on the pick up tube will answer your question, also a great way to flush a motor if used in salt water . Let us know what you find

[MNY4m4h4]

Maybe there is some disturbance causing air to be sucked into the water pump, but I would expect that to be at higher speeds.
Maybe exhaust getting into water flow

I would think about dropping lower unit and hooking up a water hose to the tube leaving water pump. turn on water and crank up motor to see if that would let motor run without overheating.
At least that would say if problem was in power head or maybe lower unit

Makes sense in that it would either identify or eliminate the water pump from being the possible problem. That said, it seems kind of wild westish ...... not gonna F up my motor doing this am I?

[99yam40]

Maybe there is some disturbance causing air to be sucked into the water pump, but I would expect that to be at higher speeds.
Maybe exhaust getting into water flow

I would think about dropping lower unit and hooking up a water hose to the tube leaving water pump. turn on water and crank up motor to see if that would let motor run without overheating.
At least that would say if problem was in power head or maybe lower unit

[MNY4m4h4]

How did the passages look when you pulled it all apart?

They looked really good, in fact the motor is in awesome condition for 25 years old.

I was hoping to find a clear blockage but found nothing. The only issue I saw was on both head gaskets there was a small tear on one end where the gasket is solid and covers a pocket. The gasket looked like it had sucked into that pocket and had a small tear in it like someone poked it with their finger.

That pocket in the head doesn't have a port or go anywhere, but I was hoping it was somehow causing the issue because I saw nothing in any of the water jacket passages to show any type of blockage.

I expected to find something and when I didn't I was hoping that a full cleaning of the water jackets and new gaskets fixed the issue....sadly it didn't.

[99yam40]

How did the passages look when you pulled it all apart?

[MNY4m4h4]

Replaced water pump, impeller and housing


Did you use the kit with cup and wear plate?

Yes, replaced with factory Yamaha kit, all the way to the keyway

[99yam40]

Replaced water pump, impeller and housing


Did you use the kit with cup and wear plate?

[MNY4m4h4]

I have a 1990 ProV 150LD that has me at my wits end. The motor runs great but overheats at idle.

I bought this used and when I first replaced the impeller I saw signs of overheating. The plastic around the cup was a bit melted. It seems reasonable to assume the old impeller burned up for some unknown reason and the seller simply replaced it and dumped his problems off on me.

I have performed the following in order as listed and I still get a weak tell tale stream, 0 pressure on the gauge (gauge could be broken), and goes into alarm in about 5 minutes.

Replaced water pump, impeller and housing
Cleaned out tell tale hose and nipple
Replaced Popit, rubber grommit, and gasket.
Replaced both thermostats and gaskets
Replaced temp sensors
Pulled water jackets on heads, cleaned and replaced gaskets
Pulled Heads and cleaned water jackets and replaced head gaskets
Pulled exhaust manifold (one that houses popit) cleaned water jackets and replaced both gaskets.
Ran a camera up the tube from water pump to bottom of powerhead and didn't find any blockages.

I was convinced I had a blockage in my cooling system but found nothing when I pulled it apart and cleaned it. I just put heads and and exhaust manifold back on and ran to launch to test and she still had the weak stream and alarm came on in first five minutes.

Heads, jugs and cylinders all look great and like I said the motor purrs but gets hot at idle. If I take it up to 1500 rpm or more then I have no issues, she only overheats at low rpm.

I really hope there is a Jedi Master Yamaha Mechanic that reads this and has seen this before!

Defeated in MN