Yamaha 250 getting hot ????????

REELPROPERTY · 07-23-2008, 11:36 AM

I have twin OX66 250's 1997 model. My starboard motor runs perfect at any speed but as soon as I get toidle it starts to creep up and gets hot...... The pee stream has always been weaker on this motor but it didn't have any negative effectsuntil now. I have had the thermostats changedtwice and the poppit valve changed twice as well......... Does anyone have any ideas as to what I can check?? I appreciate any advice or help.. Thanks, Jason

HIKE · 07-23-2008, 12:58 PM

have you changed out the water pump?

REELPROPERTY · 07-23-2008, 01:52 PM

Yes I had those changed on both motors. I really am stumped on this. I read on a forum about the same exact propblem on the same motor and it was his poppit valve.... changed it out twice to no avail. I really would like to have this fixed. I still take it out but I have to kill that motor when I need to Idle around for any time......... SUX :doh

brnbser · 07-23-2008, 02:32 PM

SET 4 Life is dealing with the same thing but on an 07 F250 w/ 250 or so hrs and it's been doing it since about 205 hrs, had a Yamaha service rep this weekend tell us he believed it was a partial blockage in the water passages

not sure if it fixed it or not but Lou ran it in a drum for quite a while with Salt Away in the drum...........

we had already done all the things you mentioned......2 or 3 new water pump kits, new poppits, etc. the F250 isn't actually overheating. It's throwing an overtemp alarm on the command link guages but the engine temp (bar graph) is still sitting at normal operating temp. basically the temp sensor is showing good but there is a thermo sensor in the top of the block and the water pressure at idle isn't making it all the way to the top of the water jacket and this sensor thus throwing the overtemp alarm.

first question would be, are you positive the engine is actually overheating or could it be a bad sensor? find the normal operating temp range for your engine and see if you can borrow a handheld temp sensor to run it andsee the actual temp of your engine when it throws the alarm.

Kenny Mann at Emerald Coast has been around and around with this one and on the phone alot with Yamaha........they're stumped also and want to know the fix when he/we find it.......

REELPROPERTY · 07-23-2008, 03:14 PM

It is funny you say that....... I have felt the water coming from the pee stream (only way I know how to describe it) and the water isnt ant warmer than the port motor running the same rpm and time...... That sounds like what may be happening......... Please let me know if they see what that might be...... I think that may be on the right track. Thanks for the help, Jason

TMS · 07-23-2008, 03:22 PM

We have seen partially blocked coolant passages on a couple of Yamahas.

The last one had salt and sand debris restricting water flow right below the high temp alarm sender.

brnbser · 07-23-2008, 05:39 PM

try the flushing with Salt Away like I was referring to. There are plastic/rubber spacers in between the cylinders on the F250's that they believe arestarting to cause problems according to some of the service reps. I'm not sure if your OX66 has the same or a similar configuration. Something along the lines of "because the water jackets are so large in the yam 250, the pressure fromflushing with a hose isn't getting all the build up and deposits out causing the blockages. That Salt Away stuff is pretty expensive, like 35-40 a gallon and follow the directions. That's where I would head first because you can do it yourself. If your problem is blockage also, don't expect this stuff to work miracles the first time you use it, it may take a couple of rounds but will eventually clean it out. The next option would be a harsh acid flush and there is a way to do it on most engines but unless your experienced at using this stuff and this method, I wouldn't try it solo. Last option obviously being pulling the heads.

DOUBLE "D" & LV · 07-23-2008, 11:42 PM

I have had a few like this. It was a minor fix. Give me a call to discuss. There are a few things it usually is.

DreamWeaver21 · 07-23-2008, 11:50 PM

Quote:

REELPROPERTY (7/23/2008)I have twin OX66 250's 1997 model. My starboard motor runs perfect at any speed but as soon as I get toidle it starts to creep up and gets hot...... The pee stream has always been weaker on this motor but it didn't have any negative effectsuntil now. I have had the thermostats changedtwice and the poppit valve changed twice as well......... Does anyone have any ideas as to what I can check?? I appreciate any advice or help.. Thanks, Jason

Did you change the spring on the poppit valve or at least take the old one out give it a good stretch and reinstall? I know you said you changed it twice but this is such a classic poppit valve symptom it is hard for me to think what else it could be. When it starts getting hot I bet you can give it some gas and it will cool back off right? Also what is your in gear idle rpm? I had mine go down to 400-500 before and it wan't pumping enough cooling water at that speed at 600 it would.

REELPROPERTY · 07-24-2008, 09:31 AM

Yes,when I replaced the poppit valve I replaced spring and all. It sounded exactly like that was what it had to be but :reallycrying has to be something else. I tried the salt away numerous times back to back and everytime I bring it out of the water I will run some through just as the directions say.... Unfortunately it still does the exact same thing.