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Engine bogging in and out past half throttle

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rryanstrickland

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Hello all. Thanks for such a great resource! I've searched and read some stuff about my problem, but none specific. I have a 1995 SeaDoo Speedster with twin 657's. For some reason when I go past about half throttle (which is moving pretty good) the left engine will start to "bogg" down for about 3 seconds and then rev back up for about 2 seconds and then back down for 3...and so on. I think the RPM range is something like 6K down to 4K, then back up to 6K and down to 4K.

The first thing I'll check today is the compression, somewhere around 150psi, but mainly making sure each cylinder matches the other pretty close.

I also read something about the jets in the carb. Something about a primary jet and a pilot jet maybe? Last year it did the same thing and I disassembled the carbs and cleaned them real good....

Other than cruizin past half throttle, it runs LIKE A TOP!!! :)

Any new ideas or thoughts?

thanks again,

Ryan
Columbia, SC
 
Did compression test...good results 150psi all cylinders

Bump...

I just did a compression test and all 4 cylinders(2 per engine) read 149 to 150 psi. I did the test with the engine cold, with throttles wide open. I've read it's best to do it with the engine at operating temp...but I figured it would be a good baseline to start with.

Anybody got any ideas about the engine surging up and down past about half throttle?

thanks,

Ryan
 
say what??? man, you crazier than a motor scooter...:rofl:

Look against the "firewall" inside of engine compartment, or in the electrical box against it. Open/look for a "yellow" 1in square look'n thing, with yellow/red/black wires from it. Disconnect the red one. If bad, it'll give the symptom your get'n...:cheers:
 
Engine bogging in and out past half throttle???

Well, I looked into the rectifier in the shop manual. It really doesn't say much about it? Does anyone think it would work perfect until I reach about 4K rpm? It will rev wide open for about 2 seconds then bog down for about 3 seconds then jump back up to about 7K rpm and then back down to about 4 or 5K?

Hmmm???
 
Try cleaning the internal carb filters. Might be clogged and the engine is running out of fuel.
 
by disconnect do you mean cut it? I checked mine out today and the only way to "disconnect" it was to cut the wire...which I did in hopes that would solve my problem...it didn't. Now I have the same problem and I have to fix the wire.
 
I kinda suspect the carbs too. I did clean the carbs and internal filters last year but who knows? I only took it out on the water one time last year and it did the same thing. It runs perfect at or below half throttle? So...

I read something on another post about the pilot jet and the primary jet. It would almost make sense that when the primary jet is supposed to kick in after the pilot jet it isn't? Someone said that the pilot jet supplies fuel only for the initial burst of fuel, once going into the higher rpm's, then the primary jet is supposed to kick in and supply constant fuel. But the jets are just calibrated inserts with "holes" in them. Maybe it's a carb fuel pump problem? :ack:


Ryan
 
cracked intake

I had the same problem for the last month...cleaned and cleaned the carbs and it ended up being a small crack in the intake manifold:hat:
 
Where on the manifold was the crack? Your boat was only acting up at higher rpms right? How did you fix it and how much did it cost you?
 
Chicks...you could've followed it to the "plug", then pop the wire out. If still problem, and since, we dont know ur situation, have you cleaned/rebuilt carbs lately?

rryan...you mentioned you went thru carbs, so I mentioned about the rectifier. You can, if you think the carbs are good, is to replace the o-rings in the inline filters.

Heres the cinerio about the rectifier...The rectifier/regulator box does two things. It recieves AC voltage generated by the stator coils through the yellow wires. It then converts that AC power to DC power using the rectifier portion. The red wire sends back to the battery, regulated DC voltage to keep your battery charged while riding the ski.
When the rectifier quits working, that red wire is sending AC voltage to the DC battery. Your ignition runs off DC power as it is a DC CDI ignition. When AC is sent, it interferes with the DC CDI. If you can picture the static your car radio has when under high power lines you can understand how the AC effects the ignition.

A magneto produces very little voltage at lower rpm and more voltage at higher rpm. That is why the motor will start and run decent at lower rpm, but run very ragged at higher rpm when the rectifier is shot.
 
T-tt-tt-t-Timmy! :)
Sounds like a pretty good theory you got there! I guess I'll have to put her back in the water and try this out. B/c your not supposed to rev this thing out the water...right? Pumps, seals overheating? Let me know....


thanks man
 
I have cleaned out the carbs but I did not take them apart so that could be part of the problem. I am having the problem on the port side motor most of the time but the starboard will act up also.
 
About the carbs, I went through them last year, but did not rebuild. I might need to do that.

Again, this wierd "top end" problem is cyclic. Somewhere about 5K rpm it starts to cycle back to 4K then back to 6K...and so on every few seconds. It's like a perfectly cycled loop. Thats what has me puzzled. I'll disconnect the red wire from the rectifier and I should see what again? A motor that boggs down more or an improvement?

thanks again!
 
Rye...if its one motor, then if the rectifier didnt change the performance, try throtl'n down on good motor around 6k, then WOT on motor act'n up. See if then, it holds 7k
 
cracked intake

a new intake is about $140.00. I have a used one on order for
$70.00. will let you know how it works out:hurray:
 
thanks Timmy.

I've only read in the service manual not to run the motor out of the water for more than 5 minutes or so b/c the pump bearings are water cooled....
 
gotcha...you mentioned "how high", so thats why I posted what i did, but your right, no more than 5min, with hose attached, but b4 turning it on, put some water on carbon ring assy, to help keep cool, for those 3-5 minutes.
 
how to check rectifier

well, I sortof checked the rectifiers, and the engine that I'm having trouble with showed a negative 12.6 volts DC at idle(3K rpm's)??? The other engine read a positive 2.5 volts DC at idle??? Hmmm, probably the rectifier that shows the funky negative reading???

BTW I grounded my negative (black) lead from my digital meter to the engine and red lead to the red wire coming out of the rectifier...

any ideas?
 
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