Yamaha T50TLR Overheat alarm.

[Sparkdr220]

I have a 2010 T50TLR. I began to get an overheat alarm in idle. I have had it into 2 mechanics. One is Yamaha certified. Both flushed and replaced fuel pump, thermostat and impeller. The Yamaha certified mechanic along with the Yamaha help line have said they can't figure out the issue. With little to loose I downloaded the repair manual and got started. I have been told this model does not have a poppet valve. Can anyone explain how to find the IAC valve? Or post a pic? I found it in the manual and it shows 2 screws holding it in place but the actual location is not clear. Any other possible solutions would be appreciated as well.

Thanks

[99yam40]

does it also overheat at higher RPM?
or is it only at idle?

[TownsendsFJR1300]

Are they sure it's overheating and not a faulty sensor?


As you requested,

Capture.JPG

[Sparkdr220]

It only over heats in idle. It also eventually will die in idle. It appears as though the water pressure is weaker than it should be. I opened up the exhaust port and and pulled out a cup of crud. Now the pressure looks great at higher rpm's but still low in idle.

Thanks for the pic. Is there anything in the way? Hard to tell from the pic if it is in the open.

[Sparkdr220]

Side note: I have to say as a retired troubleshooter...2 highly regarded mechanics and Yamaha customer service saying they can't figure it out is mind boggling. The engine has been professionally maintained and has 470 hours on it.

[99yam40]

It only over heats in idle. It also eventually will die in idle. It appears as though the water pressure is weaker than it should be. I opened up the exhaust port and and pulled out a cup of crud. Now the pressure looks great at higher rpm's but still low in idle.
.

only thing I can think of off hand is either the motor is not filling all the way up at low RPM so the top overheats because of no cooling water there,

or there is a cooling passage partially plugged up somewhere since you found all of that sludge.

but then a restricted passage would overheat at higher RPM also

so maybe a problem with water pump housing, water tube heading up to the power head, grommets the tube fits into at pump or powerhead

[Sparkdr220]

Since I cleaned out the sludge the water makes it all the way up to the thermostat. I am leaning toward improving the water pressure in idle. I think if I can figure out how to remove the iac valve, i can either clean or replace it. As i stated before...i found the valve in the repair manual, but, it really doesn't explain what needs to be removed to get to it.

[99yam40]

IAC valve is idle air control valve, so I do not see how that would help water flow

[Sparkdr220]

The water flow is good. It gets week in idle. I think if i can tweak the idle and get the rpm's up a bit it may raise the water pressure in idle.

[99yam40]

ECU controls idle RPM with the IAC.
fix your overheat problem instead of trying to jack with Idle speed unless it is out of spec

[Sparkdr220]

As i stated I brought it to 2 mechanics. 1 Yamaha certified. Both mechanics and Yamaha techs gave up. It only overheats in idle. the tell tail is strong until i put it in idle. What do you think my next move should be?

[99yam40]

read what I wrote earlier

you said they all replace the impeller, so that leaves other parts in the pump and system to look at

[Sparkdr220]

i didn't explain that very well. The first mechanic replaced the impeller. The second (Yamaha certified) told me he needed to check it to make sure it is a Yamaha part. I assumed when he had the lower unit off and worked with Yamaha techs they would have checked those items before giving up. You mentioned if there was a blockage it would cause issues at higher rpm's as well. It doesn't overheat at higher rpm's. The Yamaha mechanic told me that if it was his boat, he would just run at higher rpm's and work around the issue. That won't work for me as there are several no wake areas that i have to navigate.

[99yam40]

the pump should push enough water to cool at idle PM unless there is a problem with the pump .
there could something not letting all of that water get to the powerhead,
maybe there is a leak causing some of the water to flow out not letting the powerhead fill up.

I guess if there was a restriction causing a problem at low RPM higher RPM may produce higher pressure to push more water up there past that restriction.

you still did not answer if they just replaced the impellor or maybe a whole water pump kit witch contains the cup and wear plats along with orings and bolts.
the housing does not come with the kit so it has to be purchased separately when needed

[Sparkdr220]

I do not know. I assumed since he was in contact with Yamaha techs and he said they exhausted all options he would have thought to do that. Could a Yamaha tech and phone support miss something like that? I just ran the motor and it ran like a champ with a strong tell tail above idle. When I put it in idle the tell tail went away and I got an overheat alarm within 5 minutes. What you are saying makes sense. We have a mobile mechanic in our area that is supposed to be really good. I think I will give him a shot.