My new (to me) 96 GTX

[jjsinaz]

So I picked up this 96 GTX on CL. I've been wanting a 97 for a long time and since they're basically the same ski i figured what the heck. I did not lake test it before I bought it. Checked compression , which was good and it started and ran so I figured I at least had something to work with.

Took it to the lake late Thursday afternoon and went for a ride. Ran like crap. The guy said he had the carbs rebuilt earlier this year, but I wasn't sure if it was starving for fuel so I opened the HS screws about 1/4 turn each. This only made it worse. So I put it back on the trlr and headed home.

I have been reading alot about these kind of problems and from what I've read the symptoms seem to lean toward a bad rectifier. Coughing, backfiring, tach jumping all over the place. I took the rear E box apart That night and it looked pretty good inside, so I cleaned all the connections in there and di-electric greased them and put it back together.

Pulled the carbs off and although I've only disassembled the Mag carb, it looks clean inside and I'd have to say the guy didn't lie abut the carbs being rebuilt. I will go through them both and make sure the needle/seats aren't leaking and that the pop off is correct, which BTW, what would the recommended pop off be for this ski?

Today I tor into the front e-box, and it was not pretty. A lot of corrosion on the rectifier and looks like it has been getting moisture in it. The tops are blown out of a couple of thise things that screw on to hold/seal the wire ports, so I suspect that is where the moisture has been getting in. I think I can fix those with a little JB weld.

I'm going to clean everything up in there and replace the rectifier, since it is so nasty looking (see pic) and I also read that the rectifiers were problematic on this year/model ski. It looks liek someone might have put this one in uses, as it looks like they tried to clean the plate that it sits on in the ebox.

The other thing concerning me is that the plastic on the MPEM is cracked on the one end. See Pic. Do you think I should go ahead and use it or replace it? I don't think water could get into it and it seems like it was working okay. Don't know if this could contribute to my running issue or not

 

[Ankeneyou]

I'd say that rectifier is your issue. As for the mpem I'd seal it back up with some epoxy or silicone and see what happens. If the rectifier fixes your issue then I wouldn't worry about the MPEM.

I just picked up a minty 97 GTX myself and am very happy with it. I can't believe the power difference between my 97 GTI and the GTX.

 

[jjsinaz]

Thanks Anky,

That's what I think too. I'll seal up the MPEM with some JB Weld (love that stuff). And get a new rectifier. And if that doesn't fix it...we'll go from there. LOL

This ones far from "minty" But the guy said the engine only has about 40 hrs on it. I can see it has been worked on.

I want to get it running good before I start on the hull. I have a lot of sanding to do !!!

 

[Frank_Hassa]

I'd say that rectifier is your issue.

I found this really good Youtube video just yesterday that clearly describes the voltage rectification process and compares reading between a "known-good" and a "known-bad" rectifier. All you need is a multimeter.

[video=youtube_share;8MqQ9g3YaH8]https://youtu.be/8MqQ9g3YaH8[/video]

 

[jjsinaz]

Thanks Frank,

I did check the voltage between not running and running. And although the voltage did increase some, it was nowhere near 14 v. If memory serves, not running I have about 11.9 v and running about 12.9. (This was with an el cheapo harbor freight multi meter) Another thing, the charging system is a little different on the 787 engine. As the guy in the video mentioned, the stators are different. The 787 has a three phase stator in ti so there are actually three yellow wires connected to the rectifier. I was hoping Icould do some sort of continuity test with a ohm meter, but according to the service manual, you can't accurately test this rectifier that way. The one in the video you can. Thanks again for sharing the video and information.

Even if my rectifier checked out good, I'd still be replacing it. The one that was in there must have been used from a salt water ski because it looks like it came off the bottom of the ocean :facepalm:

 

[Frank_Hassa]

Thanks Frank,

I did check the voltage between not running and running. And although the voltage did increase some, it was nowhere near 14 v. If memory serves, not running I have about 11.9 v and running about 12.9. (This was with an el cheapo harbor freight multi meter) Another thing, the charging system is a little different on the 787 engine. As the guy in the video mentioned, the stators are different. The 787 has a three phase stator in ti so there are actually three yellow wires connected to the rectifier. I was hoping Icould do some sort of continuity test with a ohm meter, but according to the service manual, you can't accurately test this rectifier that way. The one in the video you can. Thanks again for sharing the video and information.

Even if my rectifier checked out good, I'd still be replacing it. The one that was in there must have been used from a salt water ski because it looks like it came off the bottom of the ocean :facepalm:

I looked up prices for rectifiers and they're cheap. Mentally I have a class of parts I call "disposable", when they are cheap, easy to remove and replace and when in doubt I'll drop $20.00 on a part and throw it on, just on the chance that it fixes something and I don't have to spend too much time troubleshooting.

 

[mikidymac]

Don't buy a $20 rectifier. Some parts like this OEM is the only way. Too many people here have gotten the cheap ones and they are bad out of the box.

 

[Ankeneyou]

I've been running an $18 eBay one all year with no issues, but it may be luck of the draw. I did find a NOS one for $30 recently on there if/when this one dies.

 

[jjsinaz]

Well....I've been busy. I got a used rectifier and water regulator and new carb kits from Westside Watersports. Thanks Jess!
I've rebuilt the carburetors, replaced the rectifier, cleaned all the electrical connections in both e boxes, drained the oil tank cleaned and refilled with fresh oil drained the gas tank and refilled with fresh gas, replaced the fuel tank float (it was sunk), and replaced the spark plugs. (and a bunch of other chicken $hit stuff)

Tomorrow morning I'm going to the lake to dial in the carbs and see how she runs now. Wish me luck please!!!

 

[gazza2010au]

That regulator looks average for a salt water machine we have around 5% fresh water in Australia as we are only a 4500km island at its widest so we are surrounded by salt water

i haven't dived into a GTX electrical box not just yet anyway but if it's anything like a 650 SP, 720 SPX and HX i think from bad memory there are earth wires that mount to the top of the mounting bolts that hold the regulator in place, with all this corrosion and salt build up u may have had a weak earth connection causing the erratic motion of the motor

if this electrical box was from the original ski i would be very tempted to pop the stator cover off and take a look in there as well for rust and replace the seal

keep in mind while your out buzzing about on your jetski for the whole duration of the motor running the voltage regulator is doing a job that is converting and or reducing and supplying a stable low voltage current and they look to be resin filled so they heat up and as they heat up and cool down it attracts moisture resulting in the corrosion

good luck on your test day may your problems be solved

 

[hotrodssnova]

One other thing to check is while the engine is running, you should have around 45 volts A/C between any 2 of the yellow wires going to the rectifier.
Set your tester to ac and check.

 

[jjsinaz]

Well, I think the rectifier did the trick, or at least helped. I was out today and it ran good, not great, but good. It was smooth, no missing, etc, but I could only get 6550 RPM/ 45 MPH out of it. I was expecting at least 50 MPH. What should one of these things normally rev at WOT?

I did discover that I had a RAVE meltdown on the PTO cylinder. When I came back into the shore and took the seat off, I noticed that the red adjuster was gone and the spring sticking out. Maybe that's where my extra RPM/Speed went? Looks like the bellow was split and that's why it melted down. Well now I have something else to fix.

Overall though, I was pleased with how it ran considering how badly it ran the last time I had it out

 

[jjsinaz]

I don't think this was a salt water ski, as there is no corrosion on anything else, just that old rectifier. I believe Someone put that nasty thing in there because I could see where they tried to clean up the back of it and the plate that it sits on so it had a good ground. I took all of that stuff apart an cleaned all of the ground connections and made up a ground wire that connects all three of the grounding posts together. Also greased with dielectric grease. I did check the output of the stator with the engine running, although I did not rev it up but I had about 21vac coming out of it at idle. Continuity check on it was good too.

 

[soccerdad]

You should get close to 6900 RPM out of it. The RAVE is definitely needed to get there. It opens the exhaust port timing and helps in top revs. Also check the water valve (the thing on the water box that looks like a rave cap). It meters water into the pipe and must work correctly for top revs. Of course, you also need a good fuel system. I assume compression is good?

 

[jjsinaz]

Thanks soccerdad. The fuel system is up to snuff. Just rebuilt the carbs and all, no gray fuel lines etc. Compression is 150 in each hole. I also replaced the water regulator because the old one had a hole in the bellow and the spring was broken. Got a good used one from Tonka's bro. Sounds like I'm not too far off on the RPM then. How fast does Shamu go? Can you get 50 out of her? BTW, love the work you did on her.

 

[Ankeneyou]

A good running GTX will hit 56-57 on glass so you are still missing some on the top end. I think a rave rebuild and you'll be there.

 

[jjsinaz]

Thanks. I would be ecstatic if it will go that fast. I'll get the Raves rebuilt and see. Might still need to tweak the carbs some as well. What do you have your pop-off set at?

 

[Ankeneyou]

Put the carbs back to stock settings on the high and low needles. I noticed you opened them a bit while trying to figure out the last issue.

 

[jjsinaz]

Roger that Thx

 

[Mickirig1]

Still not getting there, do a pressure check on fuel system. Probably have elderly, vents out and intakes in, on system. They should be replace every, I think 6 years. Easier to suck air then gas. look at water separator / fuel filter up front. Gaskets split or do not seal.

 

[soccerdad]

I have only got Shamu up to about 52 (GPS). But I don't do speed runs much. I also run it a little rich since I used it a lot to pull tubes. Now I have a boat so I could lean it out some. Fix the rave and I bet you pick up a lot. Thanks for the compliments on Shamu.

 

[jjsinaz]

52 is very respectable I think. I don't think I'd mess with that. Running a little on the rich side seems safer to me. Thanks for the response

 

[Frank_Hassa]

Still not getting there, do a pressure check on fuel system. Probably have elderly, vents out and intakes in, on system. They should be replace every, I think 6 years. Easier to suck air then gas. look at water separator / fuel filter up front. Gaskets split or do not seal.

What part(s) are you referring to here? I've got mine all tore open and now is the time to replace something as a preventative if it's cheap.

 

[Mickirig1]

The through the hull gas vents. They vent off pressure in system and let in air if it's needed to replace fuel used. They are fairly cheap.

 

[jjsinaz]

Do you have to get these check valves from a dealer, or are there other sources?