2000 Yamaha 115 Overheating

[Saltwater365]

Hello all,
I am new to using forums, so please forgive me if I do not follow the protocol correctly.

I have read extensively into the issue I am having, but as always, every situation is slightly different than the last. So rather than assume i know what I am doing now, I was hoping that I could just put my little story out there and see what you all have to say!

My 2000 Yamaha 115:

After a few minutes of cruising at 4000-4400 rpm, the following symptoms occur simultaneously:


Symptoms
"hot water indicator" on my dash will begin to flash
The audible alarm will sound
The engine seems to choke itself


As I pull back the throttle and return to slightly above idle, the engine cools and alarms terminate almost immediately. The tell tale pee stream is strong and cool, the top of the lower unit also cool to the touch. I have not yet been brave enough to lay my hands on the potentially burning hot heads, but the engine cover itself does not feel particularly warm.


Recent Repairs
I just did a full waterpump replacement kit and thermostats. The stats really didnt look too bad (maybe im just telling myself that to avoid pulling the heads to check for blockage)

Questions:

1. Is it possible that the Pressure Relief (or "poppet"?) Valve could be causing overheating at high rpm? (Most of the info about these valves is for engines overheating at lower rpm)

2. If the prv IS something i should be looking into, where the heck is it? and can i do this myself? Could I inspect the "screen" thats in there and not need to replace the valve?

3. Isn't there another way to clean the heads without pulling them? I really dont think that is something I can handle. Has anyone had any success flushing the engine in a bucket with some sort of salt deposit remover?

4. Could it just be faulty temperature sensors?(don't know if there is such a thing, just wishful thinking)

5. Could it be something silly? Like maybe i put the little plastic screen on the lower unit back on backwards after I cleaned everything during the waterpump replacement... Maybe the impeller is in backwards (99.999% impossible)? Im desperate not to pull the heads.

6. What should I do next?


Thank you for any advice!

Andrew

[99yam40]

Did this motor have the over heating problem before you replaced the stats and water pump?
Is this a salt water motor and is it flushed with fresh water after every run in salt?

The temp senders or switches can be pulled and tested to make sure they are functioning properly.
and the temperature of the heads and other parts can be checked with a lazer temperature gun to see what they are getting up to if there is a hot spot

[Saltwater365]

Yes, these symptoms began right before winter storage

Yes, this engine is used in saltwater.

No, it is not flushed.



You recommend I test the "temperature senders or switches".


Has that ever happened to anyone?: engine running in normal operating temperature, but the temperature switches malfunction.

And replacing them fixed the problem?

[BQUICK]

Though I can't recommend it, one mechanic told me to just pull the sensors out of the heads and let them hang. Another said to pull them out and put heavy grease on them and re-install. Either way the idea is the avoid the main issue that is buildup in the cooling passages in the heads.

Not what you wanted to hear but one of the mechanics said that some people have run many years more after doing this.

I didn't listen and tried to pull my heads. Of course one head came right off but the other snapped a lower bolt. I stopped there and now have a Vise-Grip holding the head there and am on my second season with it. And yes, that sensor has a blob of grease insulating it from the head.

More than one way to skin a cat.....

No alarms since.......

[Saltwater365]

Sounds dangerous, kinda like taking out the little light bulb behind the check engine light in your car.

I cant afford to repower yet, otherwise i would be asking questions about what prop to pair with my new 150 four stroke

[BQUICK]

Yeah, or like putting electrical tape over the temp gauge on a car.....

However, on mine the water temp was low just spiking the cylinder head temp which is not helped by the 10% ethanol fuel which causes the motor to run leaner. I bet if the main jets in the carb were increased a couple thou it wouldn't happen again....

Speaking of running lean. Check your fuel filters. 10 micron filters clog easier than 20 micron which can cause a lean condition and heat spike in the cylinder heads.
Also, weak fuel pump(s) can cause same....

[Saltwater365]

Okay BQuick,

So it is your opinion that it probably is, in fact, build up in the cooling passages.

BUT, better fuel flow COULD help overheating?


Fuel filters are cheap and simple, ill try that for sure.


Anyone else think thats possible?

[jb123]

did you also replace the waterpump housing? i would replace that and PRV parts, run and repost

[99yam40]

If you have not been flushing motor after running in salt water then you need to have the heads and other things pulled and the passages cleaned .
if the bolts do not all break off you will be very lucky.

If you want to make sure it is really over heating then test things

[Saltwater365]

So the general consensus is that:

Since it is an engine used in saltwater, It is probably build up in the water passages causing true overheating

AND

Since the overheating occurs at higher rpms rather than a lower rpms, the pressure relief valve is probably not the cause.



Great, I appreciate all the feedback, guess i have to attempt this

I suppose i will need new gaskets after i pull the heads, anything else? What should I use to clean the passages? I have no idea what it looks like in there

Any other ideas will be warmly received

Thanks Again

[seahorse5]

I suppose i will need new gaskets after i pull the heads, anything else? What should I use to clean the passages? I have no idea what it looks like in there

Corrosion buildup inside the head water passages is fairly common in the 115-130 V4 engines used in saltwater. You have to remove both the heads and water covers to clean out around the cylinder walls and the passageways in each cylinder head.