2000 Sea Doo GTI low spark

[crowderfam]

Ski runs fine at half throttle or above, but very hard to start and misses at lower rpms. Coil and plug wires are only 2 years old and computer is only one year old, but it is the junk Chinese computer off eBay for $115. But only a year old though. EXTREMELY hard to see the fire in daytime. Have to hold hat to shade the plugs and put my face like 10 inches close to the plug to BARELY see the fire. Correct plugs and already adjusted the gap to .2. Any ideas? I did notice that my other Sea Doo also had very little fire as compared to our Yamaha. Is it just a Sea Doo thing? Ideas?

 

[mikidymac]

If it runs fine at higher rpm then probably not a spark issue.

What is your compression and when was the last time you rebuilt the carb and fuel system.

 

[crowderfam]

Thanks for the questions and that sounds like a good point. As far as I can remember we haven't checked the compression, but I can do so this weekend. We bought this ski from my co-owner's longtime co-worker and we know that the ski was used very little and winterized and fogged every winter. We've had it four about four years, but were assuming little engine wear because of low hours. But I can check. We have not rebuilt the carbs and I doubt that the original owner did either, but the ski has always been babied with high octane non-ethanol plus we use the marine Stabil on top of that. One more bit of info. We put it in Sunday and it ran fine for the first 45 minutes until we parked it in the cove. It was after sitting an hour or so that it then didn't want to really fire so well. Very very very little spark. My buddy can't even see the spark at all. I can only barely see it by shading the plug as much as possible with my hat and then it is only sometimes. Waaaay less spark than our Yamaha had. Computer is 1 year old, but cheap computer off ebay. Coil and wires are 2 years old, but spark plug caps are original. I do also notice that the computer doesn't beep any longer when put the dess key on. I have two iridium plugs ordered and will check compression this weekend. Ideas are appreciated!

 

[crowderfam]

I forgot to mention that the plugs were wet with gas. dried them several times and blew out cylinders. Ultimately it did start after sitting another hour and planed off and got me back to the ramp, but still could tell it was missing at lower rpms.

 

[Ckrawiec]

I forgot to mention that the plugs were wet with gas. dried them several times and blew out cylinders. Ultimately it did start after sitting another hour and planed off and got me back to the ramp, but still could tell it was missing at lower rpms.

Check your compression....use a good guage, double check with another guage just to be sure...NO Harbor Freight guages either (JUNK). 150 psi is ideal (I believe) but both cylinders should be VERY close to each other, only a few psi OFF is ok. A wide variance indicates troubles.

Service/REBUILD the carb with a genuine MIKUNI KIT (you should have a Mikuni BN-40i carb in there and the manual says its a 115 gram spring (which may NOT be part of the Mikuni kit, so you may need to get that separately), follow the carb sticky post (top of the forum)...my bet is you will see a world of difference. Also, IF still installed....replace ALL old grey fuel lines with 1/4" black auto fuel hose, replace fuel selector switch (not just cleaning), fuel filter O-ring gasket too.....make sure the fuel tank is clean and new fresh fuel is being used.

You may also consider new needle and seat [2.0 needle & seat] which are also NOT part of the carb rebuild kit, purchase separately.

Might also want to check/verify battery and rectifier operability.....with ski running at idle (3000 on trailer/ 1500 on water) see what the battery voltage is at...should be greater than 12.7 as high as 13 + volts....smooth, not bouncing all over the meter......if its not greater than 12.7...probably a bad rectifier (or the magneto, but rule out the rectifier first).

The ski is 20 years old, she is going to have issues.

 

[Ckrawiec]

AS a follow up to the MIKUNI Spring strength I stated above [115 gram spring]...I am attaching a "MIKUNI SPRING Strength" dissertation by MIKIDYMAC from another post. MIKI has stated that if he ever has the time he would try to put together an actual chart reference for this....as SEADOO is all over the map on carb springs and the seadoo manuals MAY or MAY NOT necessarily give you the "proper" information....so this is where we rely on "hard core" experts and I have no doubt that MIKI knows his stuff.....SO, I'm jumping the gun and putting his information out there for him......Sorry dude...this info was JUST TOO GOOD to not get captured.....maybe you can flex off of it for your "chart" someday. Let me know if you want the doc in WORD format....I'm attaching a pdf here.

 

[mikidymac]

AS a follow up to the MIKUNI Spring strength I stated above [115 gram spring]...I am attaching a "MIKUNI SPRING Strength" dissertation by MIKIDYMAC from another post. MIKI has stated that if he ever has the time he would try to put together an actual chart reference for this....as SEADOO is all over the map on carb springs and the seadoo manuals MAY or MAY NOT necessarily give you the "proper" information....so this is where we rely on "hard core" experts and I have no doubt that MIKI knows his stuff.....SO, I'm jumping the gun and putting his information out there for him......Sorry dude...this info was JUST TOO GOOD to not get captured.....maybe you can flex off of it for your "chart" someday. Let me know if you want the doc in WORD format....I'm attaching a pdf here.

I can't take credit for that, it was the late great Bill O'Neal of Watercraft Magic but thank you all the same.

 

[mikidymac]

To the OP, the most important thing on these skis is the fuel system, it has to be perfect or you will get nothing but grief.

Rebuild the carb with only Genuine Mikuni parts and new needle and seats. IF the carb looks line it had not been apart and no rust on the springs then reuse them and do not think about changing them out.

Second, I just had a 97' XP with weak spark. Remove and clean all electrical connectors and open all the electrical boxes and check grounds and plugs. Coat all electrical seals and electrical box gaskets with Dielectric grease and reinstall. Cut the ziptie on the spark plug boot and unscrew then (yes they actually screw onto the wires). Cut 1/4" off each plug wire and then with just a little dielectric grease on the outside of the cable screw the plug cap back on and install a new ziptie. This should get your spark back.

 

[crowderfam]

Lots of great ideas guys thanks!

 

[crowderfam]

Update for the thread! We put in two iridium plugs and gapped them slightly down to just slightly over .2 (Sea Doo calls for .2) and the ski ran great all weekend. What we seem to be finding is that the spark is naturally weak on these things for some reason. It was the same with our 99 Sea Doo GTX. Sea Doo calls for a .2 gap and even then you really struggle to still see fire on a sunny day. We also had a 98 Yamaha and it seemed to have about five times the spark that these two Sea Doos have had. In any case it's running for now! Thanks for all the help!