yamaha f25 overheat ?

[jjjewett]

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 trolled 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 ? 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

 

[Yamajoe]

Re: yamaha f25 overheat ?

Check and or replace your thermostat is a good idea. there is more than likely an overheating occuring and your sensor is not triggering the alarm. If you cann't keep the palm of hand on the top of the engine (becareful of the moving parts) for more than 8 -10sec then you have a overheating prob.

When was the last time you changed your engine oil? Don't know, or 12 months ago; then dro you oil and replace, be good idea to replace the filter as well.

The 25hp has a warning lamp. to test remove the lamp, connect a positive jumper lead to lamp male terminal, and the other lead to female terminal. USE A 1.5v BATTERY, as you will cook the lamp using 12V. Lamp should lite. Reverse connection and lamp should not light.

 

[jjjewett]

Re: yamaha f25 overheat ?

the oil pressure light?

I have no multi-tach or control box with buzzers.

-john

 

[Yamajoe]

Re: yamaha f25 overheat ?

The 25hp tiller has a lamp to warn for over heat and low oil. The lamp is located on the front of the steering bracket i think. it has a yell/red and pink/white wires which connect to the CDI unit.

 

[jjjewett]

Re: yamaha f25 overheat ?

thanks for your the advice.

this is a remote control mode. i will check the wiring to the lamp that is there, it looks like it is just an oil pressure light.

-john

 

[800sxr]

Re: yamaha f25 overheat ?

You might also pull the thermostat and check to make sure theres not little pieces of the old impeller clogging the flow.

 

[jjjewett]

Re: yamaha f25 overheat ?

I will check out the thermostat. Should I swap the thermosensor too?

 

[jjjewett]

Re: yamaha f25 overheat ?

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?

 

[Yamajoe]

Re: yamaha f25 overheat ?

I recommend you drop the lower unit and flush the cooling system from the water tube up, through the thermostat channels, both ways.I am sure there is a cleaner to remove the buildup, check with your local marine dealer, need to ensure the cleaner is suitable for use on aluminium material.

 

[jjjewett]

Re: yamaha f25 overheat ?

so this is not normal looking?

the corrosion was probably blocking the opening of the thermostat?

-john

 

[Yamajoe]

Re: yamaha f25 overheat ?

No that T Stat is stuck and that build up of crud needs to be removed and flushed out; When you order a new one it will have a gasket, it is pretty straightforward putting the new one on.

 

[jjjewett]

Re: yamaha f25 overheat ?

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.