The be all end all "My STX 12f or 15f or Ultra LX is not running right" Thread

[Crossrip36]

That's rough. I would offer a replacement upper manifold but I scrapped like 3 of them a few months back when I was cleaning out my garage. On the plus side, the upper halves rarely corrode through so a used one is probably okay.

Sean

Yep stinks. My friend that is helping me welds pipe for a living and thinks if I cut it at the seam he can weld the new 4-1 to the manifold. I can't see a downside to it really but not sure.

[smokeysevin]

Yep stinks. My friend that is helping me welds pipe for a living and thinks if I cut it at the seam he can weld the new 4-1 to the manifold. I can't see a downside to it really but not sure.

You have to seal the internal water jackets from the exhaust gasses, welding it will likely not be an option but I am also not a professional welder so who knows.

Sean

[Axion42]

Hello everyone, great info in this thread. Disclaimer, I do not yet own any PWC but I am currently looking at buying 2 Stx-12f. One is a 2003 and runs great, the other is 2007 and has a couple issues. The main issue I'm concerned about is it will crank but can't get it to start. The dude said he took it to a mechanic and the guy told him cylinder 4 has low compression, he did not provide me with any PSI numbers. I've been reading about the 2006/2007 12fs having ECU problems and that affecting the pistons, could this be the issue? If it was the ECU that blew the piston what is needed to fix it? Just simple top end? Cylinder hone, pistons, rings, new head gasket? Any info is appreciated as I'm going to go look at the skis this weekend and possibly bring them home. He's willing to sell to me for $5000 for the pair and brand new trailer/life jackets everything. Price sounds nice, even if I have to rebuild top end. Thanks!

[smokeysevin]

On the one with low compression, pull the spark plug and inspect it. If I remember right, mine was coated in aluminum particles from the piston burning up.

Sean

[steve45]

About 5 years ago, I picked up a 2004 STX-12F and a 2005 STX-15, and a Zieman double for $2200. Neither 'Ski ran, both had bad displays, but the biggest problem with both of them was totally gunked up fuel systems. I know prices are rising rapidly, but I'd offer less than $5K since the -12F appears to have major problems. Life jackets are cheap. Don't forget, the -12F has a higher compression ratio and requires premium fuel.

[Axion42]

Ya I'm in southern California and prices for toys are threw the roof. It's the best deal I've found for 2 skis and 1 is in perfect running condition. Originally he was asking $6000 and after asking a lot of questions about the 07 with problems he came down to $5000. After looking at them this weekend I might be able to get him down a little more as I sense he wants to get rid of them.

[Axion42]

On the one with low compression, pull the spark plug and inspect it. If I remember right, mine was coated in aluminum particles from the piston burning up.

Sean

Hey Sean I've seen you talk about flashing the ECU to the '04 firmware, is this something I should be interested in doing if I do acquire this '07?

[smokeysevin]

Hey Sean I've seen you talk about flashing the ECU to the '04 firmware, is this something I should be interested in doing if I do acquire this '07?

Given that I personally have an 07 that blew two pistons (I got the ski with 35 hrs on it for $500 back in 2014 with a functional gauge) that I rebuilt, I knew it had the potential to happen again.

The 04 and 07 skis use the same fuel pump, fuel pressure, fuel injectors, map sensor, intake manifold and cams iirc. As we don't know what changed between the 04 and 07 tunes on a timing/fuel level but the 04 tune works and the 07 blows up, it was not worth keeping the 07 tune/ecu so I tried the 04 ecu and it worked. I noticed no performance difference between the stock 07 ecu and the stock 04.

Bonus the 04 tune deletes slo mode so if your gauge ever goes, you can keep riding at full power.

Ultimately its a judgement call for you. Pm for the reflash details, its really reasonable and quick. Usually I get them back in the mail the next day depending on when I get the ecu in the mail.

Like Steve said though, plan for full fuel system repair/replacements, spark plugs, pump rebuilds, oil changes, exhaust couplers, maybe lower exhaust mainifold piece, and probably the output shaft cover and water log piece under the intake manifold. Those are all common areas these older skis need attention.

Once fixed, and if properly maintained, these are great skis. I used my 04 to pull wakeboarders and tubes all day long for years and the only time I had a problem with it was when it got stored with bad gas.

Sean

[Axion42]

Given that I personally have an 07 that blew two pistons (I got the ski with 35 hrs on it for $500 back in 2014 with a functional gauge) that I rebuilt, I knew it had the potential to happen again.

The 04 and 07 skis use the same fuel pump, fuel pressure, fuel injectors, map sensor, intake manifold and cams iirc. As we don't know what changed between the 04 and 07 tunes on a timing/fuel level but the 04 tune works and the 07 blows up, it was not worth keeping the 07 tune/ecu so I tried the 04 ecu and it worked. I noticed no performance difference between the stock 07 ecu and the stock 04.

Bonus the 04 tune deletes slo mode so if your gauge ever goes, you can keep riding at full power.

Ultimately its a judgement call for you. Pm for the reflash details, its really reasonable and quick. Usually I get them back in the mail the next day depending on when I get the ecu in the mail.

Like Steve said though, plan for full fuel system repair/replacements, spark plugs, pump rebuilds, oil changes, exhaust couplers, maybe lower exhaust mainifold piece, and probably the output shaft cover and water log piece under the intake manifold. Those are all common areas these older skis need attention.

Once fixed, and if properly maintained, these are great skis. I used my 04 to pull wakeboarders and tubes all day long for years and the only time I had a problem with it was when it got stored with bad gas.

Sean

Good stuff! I will PM you for sure if I end up with the purchase. I like to wrench on stuff and all of that seems pretty straight forward and manageable with my skill set. While looking at the skis are there any main points I should look out for?

[smokeysevin]

Corrosion in general is a big giveaway but the skis are getting older which means even well maintained ones will have been wet for a number of years now.

Nowadays, the expensive parts are turning out to be the exhaust components, the gauge, and stuff like the jet pump housing where there is not a less expensive alternative to the oe parts. Used parts in those cases are a crapshoot.

If the motors turn over okay and there is not signs of water in the oil, you can be reasonably confident that the motors are salvagable.

Sean