2003 Kawasaki STX-12F Overheating

05-09-2006, 10:09 PM

I am having trouble with overheating on my 2003 STX-12F, only at idle or under approximately 5-7 mph, (ex: no wake zone). You can watch the bypass water opening at the front right and see the cool water start to get hot, then much hotter and finally turn into steam, and seconds later the overheating warning goes off. The ski runs absolutely flawless otherwise in every way except for this new problem, and as long as I keep the engine rpm above idle. I only have 200 hours on the ski and have never had any problems. I also brought it to have it checked at two different dealers who both say everything looks normal. If I hook up a garden hose to the boat when it's on my trailer, it will run fine and cool all day long at idle. This tells me that the pump or impeller is not pulling up enough water to cool the engine at idle or low rpm's. I cannot find any blockages and the impeller looks okay, (hard to tell), should I change the impeller and housing anyway? (just to see if it solves the problem?), or does anyone else have any other ideas? If I do change the impeller and housing could someone recommend what to buy, (stock or upgrade to performance, and where to buy it from), I have a factory service manual, and I am a auto and motorcycle technician, so I feel I could handle the job. Any help would be greatly appreciated! Thanks, Bernie.

Kawi-Guy · 05-10-2006, 12:52 AM

take the pump off and then remove the dual cooling mount, it has some screen type holes in the pump that vacuum up the water and keep out debris and they may be clogged.
If this is not clogged I'd change your one cooling hose that comes from the pump and goes to cool your engine, it may have some debris inside at the part where it bends. This is the one on the left as you are looking at the back of your ski from the seat opening, ( its the cooling hose on the right rear side if you are facing ahead-forward while sitting on the ski)

jfoster · 12-27-2008, 03:33 PM

Same problem here on an 05 15F. Pulled the cooling mount, no problem. Guess I need to start following hoses.

motoman96 · 12-28-2008, 01:06 AM

check your clearance between the impeller and housing. at lower rpm's, if the clearance is too much it may not be drawing the correct amount of water, but once the rpm's get higher it starts forcing water thru the cooling lines. saw an FX140 with a problem like hat an it was cuz the wear ring was wiped out, only got hot at low rpm's tho.

jfoster · 12-28-2008, 09:52 AM

We just had a new liner installed - the thick re-sleeve deal, and the clearance looks fine. We've had the ski out a couple time after the new liner, so I believe all is well there.

I just checked the hose that feed the front of the motor and it's clear - I removed it from the motor and could blow through it.

Now, when I hook up a hose to that front water port on the motor, I can also blow through that and water comes out of the pisser and from under the ski (pump area, as it's supposed to). The pressure required to push that water out was minimal - makes me wonder if maybe there is something internal to the engine or some other restrictor that is supposed to be there that might not be working? Something that makes sure enough water pressure gets to the motor? I'm sure there is no thermostat - but perhaps something in-line that I haven't found?

jfoster · 01-02-2009, 10:11 AM

I found the problem. Turns out a friend of ours had the same issue and now that I've seen it, I believe it to be a potential problem for all 04-05 15Fs.

There is a hose that goes from the bottom nipple of the exhaust (just past the first blue coupler) to the engine, under the intake - you cant miss it. Under the intake, the hose connects to a piece that bolts to the side of the head. This nipple disintegrates inside the rubber hose, creating a solid clog. The replacement part from Kawasaki has a brass nipple on it, so I think they too have identified this as an issue. You must disconnect the intake and set it down (I left it in the ski with most of the connections still hooked up) to get access to the hose end. You can re-use the intake gasket if you use some copper spray on it.

It's amazing to me that Kawasaki didn't issue a recall on this, as it can leave you stranded and can seriously damage your engine. It is bound to happen on any 15F ridden in saltwater without the brass nipple piece.

puckoach · 01-06-2009, 01:07 PM

Great post and thanks for the detail !!!!

Given the time of year, and possible widespread ramifications, this should be a "sticky".

Or, better yet, there should be a seperate thread, for four stroke kawi's.

I'm sending a request to the moderator, others should do the same.

joemama422 · 01-08-2009, 04:22 PM

Awsome info!! Thanks!

Can anyone take pics of this nipple and location too? Just curious...

puckoach · 01-13-2009, 02:04 PM

Quote:

Originally Posted by puckoach

Great post and thanks for the detail !!!!

Given the time of year, and possible widespread ramifications, this should be a "sticky".

Or, better yet, there should be a seperate thread, for four stroke kawi's.

I'm sending a request to the moderator, others should do the same.

I sent a pm to the modertor seconds after the quoted post, no response.

Just saved this thread from falling off the first page. Need others to pm the moderator as well.

puckoach · 01-21-2009, 10:46 AM

No response from moderators.

Bump