F25 overheat?

I recently purchased a 2004 Yamaha F25 four stroke electric start remote control. The guy I purchased it from said that he only put around 10 hours on it after break-in. Then the motor sat in his garage for about a year.

The first time I took it out it started up great, idled great, and after about 5 minutes at higher RPMs with 2 minutes at WOT the motor bogged down and went into what I believe is RPM reduction mode.
There was no water coming out of the tell-tale.

I took it to my local Yamaha dealer and they replaced the impeller and said that it was torn.

The next time I took it out the tell-tale was peeing great and we idled for about 5 minutes then went WOT for about 5 minutes before the motor started bogging down again. It seemed like the same RPM reduction mode. We throttled it down to idle speed and *****ed for about 2 hours. The motor ran great at idle speed.

I took it out last night and it went into what I believe was RPM Reduction Mode after about 10 minutes of ¾ throttle. It idled just fine and if I killed the motor and started it right back up I could get to WOT for about a minute before it went back into reduction mode. This time I was keeping the fuel bulb firm to rule out a fuel supply issue.

I do not have any buzzers or alarms on the control box or console.

The other think is the motor exhausts a small amount of white smoke when I kill it. It kind of hisses and puffs white smoke. Is this normal? Does this indicate some other overheating going on?

My plan is to do the following:

-Hook up a 12V LED to the overheat alarm wires to see if it actually is going off. Im not totally sure that the motor even thinks that it is overheating. Are there wires in the harness I can use for this?

-Test/swap the thermostat. What is the difference between the thermostat and the thermosensor? The replacement parts looks like it should trip at ~130 degrees. Is that right?



Thanks,
John Jewett

[neverenoughx2]

An easy way to test temp is to get those crayons for min temp and max temp they are cheap and avail online or at store. Then I would start at the intake on lower unit then therostats then you may have to make sure the pump was installed I know the dealer did but it happened to me where the housing wasnt replaced so it worked at low speed but over heated when i was hooked up

the housing was not replaced. They only replaced the impeller.

They said that they ran it in neutral for "a while" and it looked good.

There is a constant, steady stream coming out of the tell-tale.

Should I assume that there needs to be more done to the water-pump system? Is there an easy way to test to see if enough water is making it to the powerhead or wherever it needs to go?

-John

[neverenoughx2]

I dont really dont believe there is a way to check the volume of water getting through. But when I had the problem there was a normal streamof water coming out of the tell tale. I wouldnt believe it was the pump because it was replaced. So I pulled the exuast cover off in case something was in there took the thermostats out completely then I finally broke down and pulled the loweer unit off while it was in the water took the pump off I noticed a slight scarring in the housing that might have been caused by the metal cup. I didn't really think that would be it but when I replaced it never overheated again. Ever scince then I do the housing everytime. It is just to important to take chances it is very easy to do if you are a little mechanically inclined. But make sure it is an overheating problem Those crayons are great.

thanks!

i just got off the phone with the dealer and he wants to start with changing the spark plugs. Im fine with doing this but i think there is something else going on.

what about the exhaust? should I be worried about that?

-John

[neverenoughx2]

Definitly start with the cheapest things first (plugs & thermostats). It doesnt sound like ignition because of the water issues. Use those crayons to make sure it is overheating and it not fuel or ignition. But if the pump was torn then it overheated and might have done some damage to the pump housing. I dont know for sure if that is it but it is kind of coincidental. Like I said earlier It was a slight scarring on the inside of the housing so slight I really did not think it was it and almost put it back on but thankfully I changed it and did not have anymore problems. I do have alarms so I knew for sure I was overheating It is just a pain to check the pump. If you get the manuel it is very simple to do yourself.

I think Im gonna get a laser temperature gun.

I also think I will swap out the thermostat and thermosensor.

-john

It looks like it might have been the thermostat. see photos

Is there any trick to putting a new one in (i ordered a new one)?

How do I clean out the housing? It looks like the corrosion stops about as deep as the tstat went. Can I just swab it out?

Should I be concerned that there is corrosion elsewhere?

Can I flush the motor with the thermostat removed?




http://www.momentumtheband.com/john/motor/tstat1.jpg
http://www.momentumtheband.com/john/...tathousing.jpg

[neverenoughx2]

YOU can clean out the housing with a wire brush or toothbrush it is not to critical. you obvioously dont want to damage anything. You can run your motor without a thermostat but you have to put a washer inside the rubber gromet that was on the thermostat. Then put it where the thermstat was.It will leak without it. YOu can actually run it without the thermostat as long as you dont use it in realy cold water because it will not reach min temp. I usally run mine without them. If you want to see if the thermostat works or not put it in a pot of water and boil it on your stove and see if it opens. It is very easy to replace (and you should every year as a maintenence thing) just make sure you also get any gaskets that that come with it. And be careful tightening it you dont crack the housing ( i've done it). Hopefully you found it. Good luck

So I swapped out the thermostat and gasket and it seems to run without overheating. I ran it for about 15 minutes at 3/4 throttle without it overheating. I then would put it into neutral, pull off the cowling, and check the temperature with a laser pointed gun. The temp was around 140 degrees Farenheit. I hope this was the problem and will post if I encounter any more.

Thanks.