revs will not exceed 4000rpm!!!!!!

[v3n0m5]

Got a question for you regarding a seadoo I bought as a side project.

Make 1992 sea doo xp
Displacement 587cc

-Rebuilt carbs as per manual suggests

-Compression in both cylinders is 140psi
-Installed new spark plugs
-drained fuel and cleaned tank.(inspected all fuel lines and filters)

Condition:
Out of water the thing fires up no problem. Launch it in the lake and warm motor up. The unit struggles to take off and will only reach 4000rpm. Manual says it should run at 6000 +-500rpm. I checked all my carb settings and it simply will not go over the 4000rpm.

I ran the unit at the 4000 rpm and did a kill on the motor. Following this I pulled the plugs to see what they looked like. After pulling them they had the brown tinge that they are supposed to have.

I'm not sure how to get the thing to run at the specified rpms. The impeller shows signs of wear but I am not sure if that can cause the issue I am having.

Let me know what you think.

 

[Shortrun]

Can you give more history of the ski? did it ever work.
I am wondering if there is a spark timing problem?
Or could the exhaust be plugged?

 

[v3n0m5]

The seadoo has worked in the past, it seems that every time it's taken out it gives a different result but most times it results in the motor only revving to 4000 rpm with rare surges up to 5500 then back to 4000.
I have considered the possibility of it being an ignition issue since I'm ruling fuel delivery out since I have went through the entire fuel system. Next step is to ohm test stator.

What are some suggestions to checking exhaust system for blockage?? Open to new ideas.

 

[Shortrun]

I think
If it is ignition the engine will sputter or sound bad.
Partially plugged exhaust engine will sound basically ok but have a serious lack of power and lack high RPM

I can only tell you about snow mobile exhaust problems. i am new to pwc. I don't even know if they have a muffler with baffling inside.

It is a popular problem with machines stored in places where mice can make nests in the muffler. Not sure if that is even possible in a SeaDoo.

 

[v3n0m5]

I will check the exhaust system. When doing the carbs I noticed the rotary valve cover has some mild wear. I wonder if the rotary valve wasn't sealing properly if the motor would struggle to reach high rpm. Just another thought that's all.

The engine seems to run fine and idle great with no issues. The issue is from idle, press the throttle and getting it to spool up to the 6000 rpm.

 

[mikidymac]

Try it with the seat off in the water. If you have an exhaust leak it will starve for oxygen and run poorly.

 

[Shortrun]

Any intake leak will cause idle problems.

 

[mikidymac]

I think he is saying it runs ok up to 4,000 then will not go any further?

 

[v3n0m5]

That's exactly what I'm saying.

 

[Shortrun]

I think he is saying it runs ok up to 4,000 then will not go any further?

I was referring to v3n mentioning rotary valve wear / sealing. Most intake problems would show up at idle. I think.

 

[v3n0m5]

Will pull the stator cover off later and do an ohm test. Will post results from this. While I got multi meter out I will test the voltage regulator while unit is running to make sure no " irregular" electric interference is present. From my past experiences this issue would either be an exhaust/rave valve issue or a faulty Cdi or ignition coil. I'm the type of tech that likes to diagnose and repair the issue instead of changing everything until it works.

 

[v3n0m5]

Volt test came back at 12.39v while idle at 3000rpm out of water.

 

[FaceDeAce]

Do you know the history of any jet pump work done to it? The old 587 seadoo I have, had the same problem. Ran fine but just wouldnt spool up. I found that a 720 impeller was put in it. I changed it to a 16-21 and it runs like a top. What is in there for a prop?

I have a thread here in the forum with details on it. Do a search.

 

[v3n0m5]

I suspected an impeller issue and your input has certainly helped. I will pull the impeller off one of these days to see if that's the issue. I do not have any history on the pump system however I can say that the vts has been removed from the previous owner(owners). Something else to not is that there is a noticeable vibration coming from the pump when idling the unit out of the water. Any suggestions on what this noise may be?

 

[FaceDeAce]

"Some" rattling from the pump out of water is normal. It shouldn't vibe.