Clogged cooling system

[Locoharleyman]

Hello, I have a four stroke 90 and I don't seem to be getting and flow thru my pee hole unless I am up to at least half throttle and quits during idle. I have just recently changed the impeller but it still has same problem. I have never had an overheat alarm and it appears that I am getting flow thru my engine and back out. Guess my question is is there anywhere anybody has experienced a clogging spot? And yes I have checked the line in the pee hole and it's free and clear, just can't figure out why it works when throttled and not at idle like it had?

[99yam40]

Check for the PRV being stuck open dumping water at low RPMs

[Locoharleyman]

Ok, that never crossed my mind. Thanks
I attached a flow diagram if anyone ever needs it also

[TownsendsFJR1300]

Also, if there's ANY DISTORTION to the water pump housing (even with a new SS cup) it will cause loss of volume of water.

[99yam40]

also if you just replaced the impeller I would recommend you always buy the kit and replace it all, the plate and cup wear too.
If the plastic housing shows and sign of melting it has to be ordered separately as it does not come with the kit