Help! Kawasaki STX-15F Heat alarm

[Gangster]

I am a new member thank you for having me.
I'm hoping to get some insight on a problem I'm having with my Kawasaki STX 15 F 2008. it sat for about two years during Covid it was outside covered and now when I try to ride it not even 1 minute the heat alarm goes off and steam is coming out of the pisser. It goes into limp mode.
It runs perfectly with a garden hose hooked up to it I have read some messages about clogged lines, I removed everyone I could see and get to and made sure they were all flowing but still no good. It's hard to diagnose because I have to be in the water working on it for it to happen if I'm home on the garden hose it runs perfectly. Please help with any ideas thank you.

[macGruber]

Some of the problems you're having are very similar to mine except I do not have the steam issue. The last time I had a steam issue was many years ago and that was because I connected some of the hoses incorrectly when I put that ski back together. Take a look at the service manual and verify that every one of your hoses are exactly correct. If you figure out your problem, please PM me.

[kyshogan]

Im gonna guess that mud dobbers or mice have clogged it up. Hard to think a clog in pisser hole would cause overheat so would have to think more on the intake. When you put on hose you are not taking in water from the intake. So that reinforces intake. And the more I think probably mouse nest.

[macGruber]

Gangster,
Hopefully you are getting notifications of replies to your post. The situation you described is almost identical to mine and I fixed my problem. Much like yours, my 15f sat around unused for quite a while. I pulled every hose oil and water cooling and there were no obstructions other than a nominal obstruction on the water inlet hose leading to the oil cooler itself. Even after resolving that obstruction I had the same problem over and over. I replaced the exhaust manifold temperature sensor and packed the void behind the screw threads with Marine grease. Still no luck. I finally took the advice of Smokin Sevin on this forum and pulled the exhaust manifold off. By doing so you will be able to create a closed loop on the water nipples by just looping one of the hoses from one of them to the other one on the lower half of the manifold. Then fill up the water jacket area at the manifold end and look to see if any water is leaking out of the middle of the final tail exhaust segment. The part that the rubber coupler connects to. My exhaust had a hole on the inside diameter of that final straight pipe segment which was allowing the cooling water that comes directly into the coupler end to immediately escape out through the exhaust itself. Therefore, there was no way that proper amounts of cooling water whatever be able to migrate upstream into the top of the manifold and into the cooling jackets of the cylinders and cylinder head. I was getting some water up there but not nearly enough and because of that, as soon as I came off of throttle the water would empty out of the exhaust quickly causing an actual overheat condition which would then trigger the exhaust temperature sensor to alert "HEAT".

I believe that the reason why this pipe rotted from the inside is because brackish or saltwater sat down in that last segment of the exhaust pipe and just slowly corroded it out over time when it was sitting unused for so long. The previous owner had a dropped valve situation during his last ride and then let it sit around too long before he decided to sell it to me.
I highly recommend you test your exhaust manifold.

[Gangster]

Gangster,
Hopefully you are getting notifications of replies to your post. The situation you described is almost identical to mine and I fixed my problem. Much like yours, my 15f sat around unused for quite a while. I pulled every hose oil and water cooling and there were no obstructions other than a nominal obstruction on the water inlet hose leading to the oil cooler itself. Even after resolving that obstruction I had the same problem over and over. I replaced the exhaust manifold temperature sensor and packed the void behind the screw threads with Marine grease. Still no luck. I finally took the advice of Smokin Sevin on this forum and pulled the exhaust manifold off. By doing so you will be able to create a closed loop on the water nipples by just looping one of the hoses from one of them to the other one on the lower half of the manifold. Then fill up the water jacket area at the manifold end and look to see if any water is leaking out of the middle of the final tail exhaust segment. The part that the rubber coupler connects to. My exhaust had a hole on the inside diameter of that final straight pipe segment which was allowing the cooling water that comes directly into the coupler end to immediately escape out through the exhaust itself. Therefore, there was no way that proper amounts of cooling water whatever be able to migrate upstream into the top of the manifold and into the cooling jackets of the cylinders and cylinder head. I was getting some water up there but not nearly enough and because of that, as soon as I came off of throttle the water would empty out of the exhaust quickly causing an actual overheat condition which would then trigger the exhaust temperature sensor to alert "HEAT".

I believe that the reason why this pipe rotted from the inside is because brackish or saltwater sat down in that last segment of the exhaust pipe and just slowly corroded it out over time when it was sitting unused for so long. The previous owner had a dropped valve situation during his last ride and then let it sit around too long before he decided to sell it to me.
I highly recommend you test your exhaust manifold.

Im sorry I never replied. I got disgusted and dropped it off to a shop to be repaired. After bull money spent O got it back just before the season but had shoulder surgery so I wasn't able to ride and test it until recently. What I have now is that they welded up a spot in the manifold they said was rotted but I suspect It had a crack from water being trapped in it over 2 seasons. it now does the overheat thing if you idle a bit or drive slow. I had a situation where I anchored it in the water for a half hour and the cylinders all filed with water and hydrolocked the engine. After reading posts on here I was convinced the lower manifold is internally cracked and the water is going into the exhaust ports.
today I believe I got my answer. I'll try to post pics but the lower manifold appears to be cracked as suspected.

[Gangster]

[smokeysevin]

A future note, typically if they get a pinhole in them at all there are more that are just waiting to pop open.

I would say it is time to scrap that pipe and try and find a new(er) fresh one.

Sean

[Gangster]

A future note, typically if they get a pinhole in them at all there are more that are just waiting to pop open.

I would say it is time to scrap that pipe and try and find a new(er) fresh one.

Sean

im going to order a brand new one, I wouldn't even trust a used one and I don't feel like doing it twice.
aone thing that's puzzling is why the gaskets only have a tiny hole for the water to pass through and the manifolds have a much bigger opening. Seems it would cool much better with more holes in the gaskets but would that affect the pressure of the water getting up into the engine?

[smokeysevin]

im going to order a brand new one, I wouldn't even trust a used one and I don't feel like doing it twice.
aone thing that's puzzling is why the gaskets only have a tiny hole for the water to pass through and the manifolds have a much bigger opening. Seems it would cool much better with more holes in the gaskets but would that affect the pressure of the water getting up into the engine?

Couple reasons, the small holes act to set the pressure drop and flow rate through the part which are critical to making sure you have the right amount of water flowing through the part at the right speed. The flow capacity of the ports in the gasket is roughly the same as the flow area of the water line going to it.

The larger area in the part is easier to cast both from a mold shape perspective and from a mold insert removal perspective. When the part is cast, the material that makes the void where the water flows has to be removed, doing small openings or complex inner shapes means you have to be more thorough to get all the sand out once the part cools.

Sean