No Power - Throwing Parts AT It ... No Clue? 1998 GS 720

[daredevil95]

Hi, I have a 1998 GS 720, I've been throwing parts at this for the past 2 weeks. Ran fine the first few times this year then, it wouldn't start so, I hit the start button and got nothing....no sound from engine but, start button relay of something was working by the button so, I changed the plugs, wires, boots, coil, solenoid & rear electrical box wiring harness. It started right up and ran decent in the driveway and once in water....bogs or breaks up while having no power. These conditions are in the video below. I removed the jet pump housing, installed new wear ring, lubed everything and all is good. Removed driveshaft and it's straight and carbon ring seal / bellows are good.

Tried it in the water this afternoon (video) and it still breaking up or something. The only other items to tackle that I could think of is removing the head and decoking? or carburetor? IDK.....In the video below, shows the craft breaking up on the water, I used a boroscope camera to video the inside of the cylinders and compression ratio of 136 psi. I'll appreciate any and all advice?

 

[mikidymac]

A lot of the aftermarket electrical parts can cause issues so what did you use for replacement?

If you haven’t done the carb and fuel system that’s typically the first place to start on these.

 

[daredevil95]

A lot of the aftermarket electrical parts can cause issues so what did you use for replacement?

If you haven’t done the carb and fuel system that’s typically the first place to start on these.

Thanks for the quick response, I bought a Vicue coil system, Seadoo oem starter relay, NGK plugs, NGK plug boots off of amazon.....no seadoo dealers close to me and a rear electrical used harness off ebay. The wear ring I had, I bought an extra one last....can't remember where I got it from? I never heard of the brand coil I bought, could be the issue? Idk No way to test it as far as I know?

What do you recommend doing or the carb an d fuel system? change lines? rebuild or replace carb? Looks like I have the old grey lines, then seem decent? appreciate any help? Thanks, gene

 

[etemplet]

since you replaced so many parts it would really be difficult to find the the root cause. Likely as miki says, you have a fuel system issue. I'd suggest not changing any more parts and figure out what's going on. Fuel delivery problems are common. Good Luck

 

[etemplet]

Watching your video your compression readings and such leads me to believe you have low compression. Lower than your gauge is reading. Try the carbs and fuel system. Good Luck !

 

[daredevil95]

I'm gonna go through the entire fuel system this afternoon. I'm going to replace all the grey lines, fuel filter(if it has one?), clean the fuel on/reserve switch, distribution thing on top of gas tank, check valves, pull carb and clean and whatever else I find? IDK....thisski has been so reliable that I never had to really work on it, other then wear ring it's been a great ski. So, I'll hopefully sort it out soon....I'm learning! Any other suggestions are appreciated. Thanks, gene

 

[mikidymac]

You can't clean the fuel selector, they have to be replaced.

No point in pulling the carbs apart if you don't install new Genuine Mikuni internal parts.

 

[daredevil95]

I checked my fuel filter and it was loaded with blue & black small pieces of something...plastic/rubber line I'm guessing. I picked up 25' of fuel line so, I'll be changing all the lines. Gotta figure how to move tank forward, looks like 3 straps, remove the oil & gas fill tubes and maybe it'll slide forward? If not, I'll work with what i got? Removed the carb, blue & gooey in the 3 lines and some gold looking flake on the side of the carburetor. Might be brass from throttle / choke butterfly? idk.... I called my closest SeaDoo dealer, ordered a new fuel filter housing, my housing looked original and brittle. They also ordered me a carburetor that I will pickup on Friday so. it was cheap enough that I'll throw another carb on. My carb is definitely full of crap so, I'll eventually buy a rebuild kit and have a spare. I believe there is a filter in the carb so, that may of saved it? I'll keep updating this thread so, future seadoo rookies like me could see my mistakes and successes. Basically, I missed diagnosed the problem due to lack of experience on jet skis but, imo....it's cheaper or the same price as to bringing it into a shop for repair? Plus, I have new parts and spares....lol. Hope this helps someone in the future. Gene

previous posts on this problem:

My first post:
What Is This Noise? (video)

My 2nd post:
New Wear Ring Impeller Won't Spin?

 

[POPPS]

There is NO reason to order a new carb unless you dropped or recked it. If you have a strong air wand, and a good can of carb cleaner, read the carb rebuild thread, and have some patience, you can clean and service the carb yourself,

 

[daredevil95]

Oh, I'm getting desperate! Just replaced every fuel line, new fuel filter and housing and a new carburetor. I properly adjusted the carb and I notice a big difference but, the same exact bogging/breaking up (not sure) so, fuel system was not the problem. So far I changed, plugs, wires, coil, solenoid, rear electrical box harness, new battery, all fuel lines, fuel filter assembly and a brand new Mikuni carb also a new wear ring. I'm guessing at this point its electrical? Anyone have a recommendation? Rectifier? Stator? it runs great in my driveway but, bogs/breaks up in the water. Same as before in the videos. Any help is appreciated. Thanks, Gene

 

[KyleW2]

I’d test the compression again with another gauge just to rule out the possibility of low compression

 

[mikidymac]

Did you replace the fuel selector? I didn’t notice it on your list.

 

[daredevil95]

Did you replace the fuel selector? I didn’t notice it on your list.

No, I didn't replace fuel switch, I did take it off and it was clean inside. The only thing that I did not mess with is the fuel pickup in the tank. I have no idea how to remove that? Think I have to remove the steering? So, I'm going to try running the ski on a 1 gallon gas tank and see how it goes? This is the last part of the fuel system to be verified to work....We'll see what happens this afternoon? Wish me luck! This is a weird situation, the first 2 rides after winter, jet ski worked flawlessly then, it sat for 2 weeks and this problem surfaced?? has me baffled; especially this ski has been super reliable....never an issue.

 

[mikidymac]

You can't clean the selectors as the rubber inside goes bad then they suck air and cause you to go lean.
Replace it.

 

[daredevil95]

You can't clean the selectors as the rubber inside goes bad then they suck air and cause you to go lean.
Replace it.

ok, sounds good and I'll play with voltage/rectifier today. If it does run correctly today on the 1 gallon gas tank then yes, fuel pickup and selector will be replaced.

 

[daredevil95]

I just checked the rectifier and it checks out at 13.9V but, when I tried to test the stator, 2 yellow AC wires in the harness I didn't get a reading.....then my battery died? It's a new battery. I have run the ski a bunch of times testing it after every repair attempt/waste of money so, maybe the stator isn't working? what's the easiest way to check on the stator? Thanks, gene

 

[mikidymac]

Test procedure is in the factory service manual that you can download for free.

 

[daredevil95]

I might have to take this in to the shop? Checked stator and resistance was .3 with parameters being .1 to 1.0 so, that checks out good? Rectifier checks out at 13.9v when revving, battery shows 12.8 not running and 14.2 while running. I don't think it's the charging system? The only other option is to run it on a seperate tank of fuel and determine if the pickup is bad? or fuel selector? Any other suggestions? The only good thing out of this issue is that I now have intimate knowledge of my jet ski so, thats a plus and automotive & PWC's have a lot in common but, totally different at the same time! I'm learning? Anything else I should check? any suggestions?

 

[mikidymac]

Remember where I suggested the fuel selector?

Run a single line from the RES fitting on the tank directly to the carb and try it.

 

[daredevil95]

Remember where I suggested the fuel selector?

Run a single line from the RES fitting on the tank directly to the carb and try it.

Thanks, I appreciate that advice! i will do this tomorrow afternoon, Ill try running it from the reserve first and if no luck, I'll bring a another tank with me and run from a seperate tank! This will confirm selector and tank pickup? Thanks again. Gene

 

[daredevil95]

Still no luck! Tried running ski on a separate tank, no good, same bogging/breaking up. I called a shop here in CT and the soonest date is Aug 5th....lol. Anyways, he spent about 20 minutes on the phone with me going through the symptoms and what I did to date to the ski. He's convinced it's the regulator/rectifier. He said it's not supposed to go over 13.8v and mine was hitting higher at times and this causes the motor to power down. Which gives the bogging/breaking up sensation. So, we'll give it a try? Can't hurt at this point....I'll keep updating this thread for future reference for a new to jet ski's guy like me. The saga continues but, we'll get it!!??

 

[Saludadoo]

Yes there's a trick disconnect the red wire from the voltage reg and see it that fixes it.
that lets the ski just run off the battery.
mine 787 ski was up to 18 volts with a bad regulator

 

[daredevil95]

Yes there's a trick disconnect the red wire from the voltage reg and see it that fixes it.
that lets the ski just run off the battery.
mine 787 ski was up to 18 volts with a bad regulator

That's great advice; thank you! I will try that tomorow.

 

[daredevil95]

The saga continues.....I received the new regulator today, installed new regulator and no good, same problem! I called the 2stroke guy here in CT and he said bring it over. He used his seadoo scanner and checked my MPEM & DESS key and both checked out good. he then checked the stator and that checked out good. He then proceeded to super high rev it and it bogs down like it's running out of fuel and stalls. It's a new carb (same symptoms as old carb) new fuel lines, filter and I ran it off a separate tank and same problem. So, he says the problem is with carb/fuel or the new coil is bad. He is backed up until august so, I'm on my own. There is nowhere else to take the jet ski to around here in CT so, I'm kinda screwed? lol I'll try another coil as soon as I can get another and/or de-coke the head. I'm open to any suggestions??

New Marine Deep Cycle battery
New coil
New Solenoid
New rear box electrical harnass
Added a 2nd ground to the rear electrical box
New plugs
New wires
New Fuel filter housing
New fuel lines
New carburetor
Fuel vents are good
New rectifier
New wear ring
Carbon Seal is like new
Bellows like new
Jet pump housing is good bearings...etc
Compression is 140ish
All fuses are good and correct size
Cleaned all grounds

So, like I said, i'm at my wits-end! lol...bottom line it has no power in water, feels like it's breaking up or bogging. It wont rev high but, doesn't stall in water. On the trailer, rev to wide open throttle and hold there and within a second it bogs down and stalls while holding the throttle WO. IDK??? help?

 

[POPPS]

Did you load test the battery?...did you go through EVERY connection?,,maybe hidden corrosion lurking?,,,is the stator charging???,