'97 Sportster Loss of Power

[Kreg]

I'm new to the Boating scene and I'm already wondering why I got in it. I bought a 1997 Sea Doo Sportster that was supposed to be in good running condition. I took it out the first time and I thought it seemed a little sluggish when I advanced the throttle. When I pushed it over half throttle the rpms came up, but no speed/thrust. Sorry, there is no tac on it. After reading some of these forums, I pulled the pump assy and found that the impeller was nicked up pretty good, so I ordered a new impeller and wear ring. With the help of one of these threads, I replaced the impeller and wear ring, and went back to the lake only to experience the same problem. When I advance the throttle over halfway, the engine revs very loudly and the back end of the boat kind of sucks down as if trying to get traction, but no speed. I think I understand what you mean when you say "plane" and my boat doesn't want to do that. It won't really level out and glide. It seems like the rear end is always dragging almost like it can't get out of first gear. The clearance on the wear ring is very tight, so I'm wondering if I s/b looking elsewhere. Any suggestions?

 

[rusty nail]

max clearance from impeller to wearring is .04". or could be carbon seal leak.
search "cavitation" in the forums.....you should find your solutions.

 

[Kreg]

max clearance from impeller to wearring is .04". or could be carbon seal leak.
search "cavitation" in the forums.....you should find your solutions.

Thx for the reply. I'm pretty sure my clearance is minimal. I have no water in the hull, but you think it could be carbon seal anyway? I'm beginning to wonder if the splines on the driveshaft or pto could be bad.

 

[rusty nail]

I was going to tell you about the splines, but if you are getting some thrust and the lack of thrust only happens when you load up the throttle, it has to be cavitation.

 

[rusty nail]

Did you use a neoprene seal when you bolted the pump housing back onto the transom?

 

[Kreg]

There was no neoprene seal when i took it off. I just sealed it with some marine grade sealant after I re-installed it. Does that need to be air tight around the pump housing?

 

[Kreg]

The more I read, the more I think you are right about the cavitation. Back to the fact that I'm not getting water in the hull - does that eliminate the carbon seal issue?

 

[rusty nail]

Pump needs to be sealed to transom. I always use the neoprene seal. carbon seal needs to run smooth with no wobble. If the engine is out of alignment this could cause air to be pulled In through the carbon seal.

 

[rusty nail]

Are you watching the carbon seal when you throttle up on the water? I have had a carbon seal look not too bad . Ended up putting a carrier bearing on and it solved the cavitation on that machine

 

[Kreg]

OK, so when you say neoprene seal, are you talking about some type of gasket because I'm not seeing one in my parts diagram? Will the carbon seal wobble when I throttle up if it is bad?

 

[rusty nail]

I do not have a lot of experience with the carbon seals not working to know what the symptoms look like, whether water comes in or not. I just use the neoprene seal regardless of whether the parts list it or not. Always had success with it and I hate working with the sealants and scraping them off . Do a quick search if neoprene seal Sea-Doo and I am sure you will find it. Make sure you get the right pump size. Yes. It is a gasket with one side that is self adhesive that I mount to the hull side.

 

[rusty nail]

I just read what I wrote. I should have started another paragraph when I started to talk about the neoprene seal.

 

[Kreg]

Great - TY! I am with you on scraping sealant!!

 

[wayneh]

Another vote for cavitation. It's how your boat will behave if you ever get into weeds and the impeller gets starved for water. RPM shoots up, boat goes nowhere. These jet pumps seem a little touchy about that and even a fairly small air leak will cause cavitation.

 

[Kreg]

Another vote for cavitation. It's how your boat will behave if you ever get into weeds and the impeller gets starved for water. RPM shoots up, boat goes nowhere. These jet pumps seem a little touchy about that and even a fairly small air leak will cause cavitation.

Thx for the additional insight. I have installed the neoprene seal and I'm anxious to try it out again. Is there any reason to goop it up with marine sealant, or do you think the neoprene seal will suffice? Also, is the carbon seal the only other place I need to worry about cavitation issues, or should I be checking something else?

 

[wayneh]

Do you have the service manual for your boat? Pump installation and sealing is addressed in the "Propulsion System" chapter. Sea-Doo allows these files to be copied and shared – I asked. I can supply my chapter 9 but getting the manual for your model would be better, and worth your time in the long run.

Greasing the front spline can reduce cavitation because the pressure of the grease pushes the drive shaft back and places just a bit more pressure on the carbon ring. This may not be your problem, but something to notice from routine maintenance.

The carbon rings can wear like a brake shoe and they can be replaced. I've never done it. There's probably a recommended thickness and if yours are more worn than that, it's a possible source of a cavitation problem.

 

[Kreg]

I ordered one on-line. I will take a look at that. Do I need to crowd that ring seal carrier up against the carbon seal, or doesn't that matter so much?

 

[Kreg]

Pump needs to be sealed to transom. I always use the neoprene seal. carbon seal needs to run smooth with no wobble. If the engine is out of alignment this could cause air to be pulled In through the carbon seal.

THANK YOU!!! Took it out after installing the neoprene seal and had NO issues!! That was fun! Thank you so much!

 

[rusty nail]

np. glad it worked out.