98 seadoo gsx not reaching top speed?

[Marc 123]

Hello everyone,

Finally, after two years, I have got my 98 seadoo gsx limited going (red and purple). I recently had a full rebuilt, with all new internals, 951 engine purchased from SES engines installed professionally. I am getting about 7100 rpm and the top speed on the speedometer is about 56mph (I don’t know how accurate this thing is). After doing some reading, I believe I should be getting about 63mph out of this thing.

any suggestions on what I could do to reach those speeds?

I don’t believe the pump/impeller has been redone and I’m not sure if that could be it or if it is needing replacement? And the carbs and fuel lines were also redone when I had the engine installed

Any help would be appreciated!

thank you!

I have provided pictures of what the impeller and ring look like.

 

[JJinSC]

1) that speedo is not accurate. Use GPS to check.
2) if you are getting 7100 RPMs any lack of speed is not from the engine.
3). It is hard to tell from the pictures, but your wear ring may be worn. Some of the gaps look beyond specs. Check it with a feeler gauge.

 

[Marc 123]

Ok, I’ll use a gps to check the speed.

And ok, good to know!

I’ll try and post some better pictures, I guess that is my main concern, if my impeller and ring need to be replaced? I’ll use a feeler gauge to check the space. Do you know what the space should be?

thank you for your time.

 

[JeremyD615]

Yes, you have too much clearance between the wear ring and impeller. It should be 1mm or less. It’s a relatively simple job, and you’ll need a new ring, an impeller tool, a new neoprene seal, a new o-ring for the pump cone, and you’ll need to change the oil in that cone. It takes about an hour to do the whole thing as long as someone didn’t glue the pump onto the hull...

 

[Marc 123]

Yes, you have too much clearance between the wear ring and impeller. It should be 1mm or less. It’s a relatively simple job, and you’ll need a new ring, an impeller tool, a new neoprene seal, a new o-ring for the pump cone, and you’ll need to change the oil in that cone. It takes about an hour to do the whole thing as long as someone didn’t glue the pump onto the hull...

 

[Marc 123]

Ok! Thank you! I’ll replace all those things and post an update soon.

 

[Marc 123]

I ordered this stuff that will be here Wednesday.

Is there anything else I will need to do this job correctly? Watching YouTube videos, I believe I need grease as well. If so, what types? And are there any other lubricants/parts I need?

Also any more tips to do this job would be great. I want to do this right and want to avoid taking it to a professional shop.

 

[JeremyD615]

You’ll have everything you need there with the exception of some marine grease for the driveshaft splines. You’re actually going further into the pump than you needed to with the complete rebuild kit and impeller, but it will be like new when you’re done. Which impeller did you buy? Some of them will gain a bit of top end and some will lose a bit of top end while gaining low end grunt...

 

[Marc 123]

You’ll have everything you need there with the exception of some marine grease for the driveshaft splines. You’re actually going further into the pump than you needed to with the complete rebuild kit and impeller, but it will be like new when you’re done. Which impeller did you buy? Some of them will gain a bit of top end and some will lose a bit of top end while gaining low end grunt...

Solas impeller ST-CD-15/20 is what I purchased. Is this a good one or do you have other recommendations? And thank you for your feedback. I’ll purchase that grease as well.

 

[JeremyD615]

I think the 15/20 is correct for your ski... People have good things to say about the Concord series impellers. I haven’t tried one myself, but it should be a good all-around choice.

 

[RockwallRick]

There is a thread in the " how to " section for changing the Wear Ring. The hardest part for me was removing the impeller. It was very hard to break loose!

 

[Marc 123]

There is a thread in the " how to " section for changing the Wear Ring. The hardest part for me was removing the impeller. It was very hard to break loose!

Thank you! I’ll definitely look that up!

 

[JJinSC]

The hardest part for me was removing the impeller. It was very hard to break loose!

A good bench vice helps with this.

 

[RockwallRick]

Yeah, I could not have done it without my bench vice plus a 4 foot pipe for extra leverage!

 

[Marc 123]

So, today I was able to get some test runs in before swapping the impeller, wearing, and jet pump bearings, seals, and shaft.

I reached a top speed of 59.6 mph on gps going down river with the current (5mph). The max rpm was 7140.

Hopefully I’ll gain some speed after the rebuild. I’ll update once I do.

I’m going to have a shop do it July 15th. I don’t want to make any mistakes...

Thanks everyone who replied with feedback.

 

[JJinSC]

One more thing that can affect top speed, and I am not sure what the top speed should be on that model, is the VTS. Make sure it is working and trimmed appropriately

 

[Marc 123]

I believe the top speed is 63ish mph, from what I’ve read.

And I believe it is leveled out according to a shop, but not 100 percent sure. I am waiting on the “trim fix” from eBay to get that working again.

 

[JJinSC]

If it’s like the XP, it will run fastest just above level. Just before porpoising.

 

[JeremyD615]

I wouldn’t go crazy over top speed numbers on this thing. There are a lot of variables, so if you’re getting into the high 50’s after the pump refurb, don’t be disappointed. That’s a strong running ski, as it takes glass water and perfect conditions to reach published top speeds...

 

[Marc 123]

I wouldn’t go crazy over top speed numbers on this thing. There are a lot of variables, so if you’re getting into the high 50’s after the pump refurb, don’t be disappointed. That’s a strong running ski, as it takes glass water and perfect conditions to reach published top speeds...

very true!

 

[Marc 123]

If it’s like the XP, it will run fastest just above level. Just before porpoising.

good to know, thanks!