Possible Rectifier?

[Espo]

Hey guys I have a 1998 speedster amd I'm having issues with one of the engines really boggy between 3500 and 6500 rpm . I just serviced the rav valves and new fuel filter and nether of these seemed to do anything so I'm wondering I was told by someone with a ltttle nolage that It could possibly be the rectifier. I was leading to a carb issue but if anyone has any knowledge on this I would appreciate it .It runs so great wide open but it's weird that it boogs out till it gets to 6500 rpm and goes like stink after that.Any help would be great.

 

[Sandman251]

I'm a little confused. Are you saying that it runs up to 6,500 RPM and then starts to bog? How long do you run the boat before it starts to bog down? Next time you have the boat out and it starts to bog, pull the choke for that motor and see what happens. Does it puke out, or get a shot of RPMs? Also I think those 787s should be closer to 7 K RPMs WOT. Before you do anything in terms of troubleshooting, check the compression. There are plenty of great resources on this forum to tell you exactly how to perform the test.

 

[Espo]

Between 3500 and 6500 it is boggy then WOT clears up and runs great .ill do a compression test today just to be sure. I'll keep you posted

 

[JeremyD615]

The rectifier is a possibility, but this sounds more like a carb problem to me... You can test the rectifier by disconnecting the red wire that goes into it. If the problem clears up, you need to replace it. Just keep in mind that the battery is not charging when it’s disconnected. Also, if you have to dig into the carbs, only use OEM Mikuni parts. Don’t let anything aftermarket anywhere near the carbs!

 

[Espo]

Does any one have a part number for the carb rebuild kit I can't seem to find it any where

 

[JeremyD615]

OSD Back To OEM Sea Doo Dual Carb Rebuild Kit (Some 1998-1999 Jetboats) [OSD1277] - $109.99 : SEA DOO Yamaha Kawasaki Polaris Parts - OSD Marine, Your ONE SOURCE for DISCOUNT Parts!

This is the kit you need...

 

[Ckrawiec]

I'm siding with JeremyD615....your problem sounds more "carby" than electric/rectifer.

I can certainly see where the mid range rpm situation might lead you to think rectifier, since one might make the leap to think you are not getting full SPARK (because the battery is low/draining) and can't feed the ignition coil adequately BUT then all of a sudden it fixes itself at higher rpm....nah, I can't take that leap with you.

If the rectifier is NOT producing voltage (Sorry, poor choice of words...rectifiers don't produce electric, only convert AC to DC, so the stator is actually producing the electric) to keep the battery maintained for full spark and the next start cycle....it won't magically fix itself at a higher rpm (how could it even get there IF it is already struggling just to get you to mid rpm's???)....so in all likelihood, the fuel system is not giving you full flow throughput......so even with full SPARK available....inadequate fuel -> inadequate power -> lower rpms (bogging) = carburation. JeremyD knows his stuff!

 

[Espo]

I'm a little confused. Are you saying that it runs up to 6,500 RPM and then starts to bog? How long do you run the boat before it starts to bog down? Next time you have the boat out and it starts to bog, pull the choke for that motor and see what happens. Does it puke out, or get a shot of RPMs? Also I think those 787s should be closer to 7 K RPMs WOT. Before you do anything in terms of troubleshooting, check the compression. There are plenty of great resources on this forum to tell you exactly how to perform the test.

I'm a little confused. Are you saying that it runs up to 6,500 RPM and then starts to bog? How long do you run the boat before it starts to bog down? Next time you have the boat out and it starts to bog, pull the choke for that motor and see what happens. Does it puke out, or get a shot of RPMs? Also I think those 787s should be closer to 7 K RPMs WOT. Before you do anything in terms of troubleshooting, check the compression. There are plenty of great resources on this forum to tell you exactly how to perform the test.

Compression is 140 on PTO and145 on mag side

 

[Espo]

I'm siding with JeremyD615....your problem sounds more "carby" than electric/rectifer.

I can certainly see where the mid range rpm situation might lead you to think rectifier, since one might make the leap to think you are not getting full SPARK (because the battery is low/draining) and can't feed the ignition coil adequately BUT then all of a sudden it fixes itself at higher rpm....nah, I can't take that leap with you.

If the rectifier is NOT producing voltage (Sorry, poor choice of words...rectifiers don't produce electric, only convert AC to DC, so the stator is actually producing the electric) to keep the battery maintained for full spark and the next start cycle....it won't magically fix itself at a higher rpm (how could it even get there IF it is already struggling just to get you to mid rpm's???)....so in all likelihood, the fuel system is not giving you full flow throughput......so even with full SPARK available....inadequate fuel -> inadequate power -> lower rpms (bogging) = carburation. JeremyD knows his stuff!

Make sense to me carb kits ordered thanks guys I'll keep you posted

 

[Ckrawiec]

Make sense to me carb kits ordered thanks guys I'll keep you posted

Follow the CARB REBUILD sticky post religiously and fastidiously.....use ONLY GENUINE mikuni kits. Take your time, DO ALL THE STEPS...re-assembly into the ski is just as important as getting the carbs all squared away too....cable adjustments need to be checked and dialed in, etc....all the systems need to be in sync with each other (electric, fuel, spark) to get the ski going right = FUN

 

[Espo]

Up date I got the carbs done by a local shop and the engine I was having trouble with now runs like a dream ,problem now is with the good engine that I wasn't having any issues with. now when it's wide open it runs great and at low idle it sounds like it's running on one cylinder and snuffs out and is hard to restart after words any possible ideas ? And by the way when I cleaned the RAV s on this engine I found a broken valve on one of the cylinders.I replaced it and was wounding if this could be a cause? It was broken for a while judging by the Carbone build up on the valve and after I changed it ran for a good hour and runs great WOT Any ideas would be great

 

[Espo]

The rectifier is a possibility, but this sounds more like a carb problem to me... You can test the rectifier by disconnecting the red wire that goes into it. If the problem clears up, you need to replace it. Just keep in mind that the battery is not charging when it’s disconnected. Also, if you have to dig into the carbs, only use OEM Mikuni parts. Don’t let anything aftermarket anywhere near the carbs!

Hey I redid the carbs and the engine I was having trouble with now runs like a dream ,but the engine that wasn't having trouble i also did the carbs on and is now stalling and running rough . Almost sounds like its running on one cylinder at idle and has hard time starting .but when it gets going it past 4000 rpm it runs great could it be just a low idle setting or something any info would be great also I found a broken rav valve when I was cleaning them and replaced it but it seems like it was like that for a while .

 

[POPPS]

Try opening the idle 1/4 turn. Your symptoms seem carb/fuel related, since it eventually opens up. Do your engines have the same rpm on your tachs? Perhaps Sync the problem motor to your good one.

 

[Espo]

Try opening the idle 1/4 turn. Your symptoms seem carb/fuel related, since it eventually opens up. Do your engines have the same rpm on your tachs? Perhaps Sync the problem motor to your good one.

I tried that and the engine is able to idle now but it still running on one cylinder and when I open it up past 4000 rpm after a few seconds it clears up and runs ok but as soon as you pull off the throttle it does the same thing again .