Yamaha 250hp 4stroke Kicking water out exhaust relief port

v12mac

Chief Petty Officer
Joined
Oct 30, 2003
Messages
502
Yamaha 250hp 4stroke Kicking water out exhaust relief port
The other day I noticed a buddy?s Yamaha 250hp 4 stroke was kicking out a lot of water through the exhaust relief port on the back of the motor at idle. Usually I see some splatter but this thing was kicking out about as much as if you were to dump a full beer out over the exhaust port. Is this normal? (The water not the wasting of a perfectly good beer.) The motor was apart in the last year due to an overheat.

Ideas?
 

DMSOUTH

Cadet
Joined
Nov 19, 2007
Messages
27
Re: Yamaha 250hp 4stroke Kicking water out exhaust relief port

Sounds like the pressure relief valve is stuck open.........
 

v12mac

Chief Petty Officer
Joined
Oct 30, 2003
Messages
502
Re: Yamaha 250hp 4stroke Kicking water out exhaust relief port

I am not an expert on this motor, is that a big deal? Can he run it like that for the season? This motor's cooling system was packed with sand and that caused the over heat a while back, any chance this could have been missed in the rebuild? or is it packing up with sand again?
 

DMSOUTH

Cadet
Joined
Nov 19, 2007
Messages
27
Re: Yamaha 250hp 4stroke Kicking water out exhaust relief port

Should be checked before running it much--at idle the prv is closed, allowing cooling water to reach the top cylinders. At higher RPMs, the valve opens and dumps excess water. If stuck open, the upper cylinders will overheat.
 

v12mac

Chief Petty Officer
Joined
Oct 30, 2003
Messages
502
Re: Yamaha 250hp 4stroke Kicking water out exhaust relief port

Thanks, I'll politely tell him to get it checked. But, you know the old "F-it! It is under warrantee" mentality....
 
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