Idle overheating

[Blizzard]

If my 1998 250 Salt Water Series idles for more than 5 minutes the overheat alarm sounds. It cools down as soon as I start moving. The motor does not have any growth on it - the impellor was replaced last week.

Is this normal??

[skeeterzx200]

Blizzard, If you find out let me know! I have a 2001 Vmax 200 with similar problems. First I replaced impeller and o rings, same thing, next I replaced impeller housing, new o rings, water tube grommet, a little better but not much. If I idle for more than 3-4 minutes the buzzer goes off. Not much water pressure at idle. Less than 5#. 18-20# at wide open throttle 5500 rpm. Was reading another post that mentioned a check valve on the Vmax 250 but not sure if my 200 has it. I am going to try thermostats next and look on this web site for check valve. Ihavce bought all of my parts from Boats.net at a great savings and with great service. I will continue to be a loyal customer.

[Ken]

Skeeter and Blizzard,
Two things to check: thermostats and pressure relief valve.
The thermostat(s) could be sticking and not opening up all the way to allow enough water at idle to cool the heads. Remove them and test in heated water per the manual - they should be fully open at 140 degrees.
The pressure relief valve could be partially stuck open and allowing too much cooling water from the water pump to bypass the water jackets. Remove and check for deposits/sticking per the Yamaha manual.
Good luck,
Ken K

[FishFinder]

I would agree with Ken, I would start with the pressure relief valve (grommet, spring, & plunger) as it will regulate the pressure in the heads. When I first got my Yamaha I put a water pressure gauge and was told the water pressure was fine. I replaced the relief valve and it almost doubled the water pressure. Next I would do the thermostats.. Cheap insurance.

[Wylie]

Hello Guys...let me join your "club". I have a 2003 HPDI/200 with a problem very similar to what you are describing. When I put it in the water and start it after about 3-4 minutes at idle, the overheat alarm starts singing. I put it in neutral and rev it up for about 3-4 minutes and it eventually stops singing. During this period of "singing" I am not registering any noticeable amount of pressure on my water gauge. However, when the overheat buzzer stops singing, I notice that the gauge is beginning to register 8-10 lbs of pressure. I thought my problem might be related to pump priming issues. Are these symptons similar to any you are experiencing?? Thanks

[Wylie]

Hello again. One thing I forgot to mention is that all during this time, I am getting a steady stream of water from the "pee" hole. It's not that I don't see water being pumped; however, I can't really tell how much water is really being pumped. Thanks.

[Ken]

Wylie,
Sure sounds like a PRV stuck partially open. Usually when this happens, you will see water coming out of the two exhaust holes that are at the top of the upper casing.
Good luck,
Ken K

[skeeterzx200]

WYLIE, THIS SOUNDS JUST LIKE MINE. KEN AND FISHFINDER THANKS FOR THE INPUT, WILL CHECK PRV THIS WEEKEND AS WELL AS THERMOSTATS.

[Blizzard]

Where is the pressure relief valve? I can't find it in the repair manual

[Ken]

Blizzard,
On my C115, it is located at the bottom of the exhaust cover/plate that is between the two banks of heads. Look for a small dome shaped metal cap that is held in place by two bolts and has a rubber hose attached to it. The PRV, I think Yamaha refers to it as a pressure regulator, is located under the metal dome.
Good luck,
Ken K

[skeeterzx200]

KEN AND FISHFINDER, THE PRV WAS MY PROBLEM! I TOOK IT APART FRI NIGHT AND FOUND DEBRIS (TINY ROCKS) HOLDING IT PARTIALLY OPEN. CLEANED IT UP AND POLISHED EDGES OF PRV SLIGHTLY SO YHAT IT MOVED FREELY AND REINSTALLED. SPENT ALL DAY SAT. FISHING WITHOUT THE FIRST OVERHEATING PROBLEM. IT ALSO INCREASED MY WP BY ABOUT 5# THANKS AGAIN!

NOW, WHAT ABOUT A ROUGH IDLE, LOW IDLE ON START-UP. DOES EFI HAVE AN IDLE ADJUSTMENT OR IS THIS CON*****ED BY ENGINE MANAGEMENT SYSTEM. SOMETIMES, HAVE TO START 3-4 TIMES TO STAY RUNNING AND IT SEEMS TO (FLOOD) THUS THE ROUGH IDLE.

[kingfish]

Similar problem with our 2001 OX66 225; just swapped out PRV (different design now from OEM) and our problem is fixed. See thread entitled, "OX66 225 low speed overheat".