Yamaha Jet Boat Delayed Acceleration (help)

[dwall2181]

Hi all,

I'm in my first season with my new to me 2006 Yamaha SX210. After a great first season, I've noticed a delay in acceleration that seems got worse over the last couple trips out.

Oddly enough, when accelerating one engine seems to rev the rpm's way up but there is maybe a 20 second delay or so before thrust/acceleration then the rpm's will drop noticeably as the thrust/compression kicks in. It feels like the engine is putting out the rpm's but there's a delay in compression from one engine or impeller, but I can't be sure...I've checked the impellers and don't see any visible objects in the jet intakes.

Anyone here seen this type of issue or have ideas on how to fix?

Appreciate any help to get this baby back running smooth!

 

[haknslash]

Sounds like cavitation to me. How do the edges of the impellers look? Any dings or chips? It doesn’t take much to cause cavitation. Does the sensation remind you of a slipping clutch or spinning tires in mud that eventually “catch”? If so, that is what cavitation feels like. RPM’s will be up there but there is little thrust.

Also check to make sure your clean out plugs are seated and sealing good.

 

[traderfjp]

I'm a newbie here so I'm just going off logic and process of elimination. Is it possible to turn one engine off and try each engine separately to see if one engine is still acting wonky? I think I read that you have to keep your speed down when running on one engine. I'm sure someone will chime in with better advice.
Good luck

 

[Babin Farms]

I'm a newbie here so I'm just going off logic and process of elimination. Is it possible to turn one engine off and try each engine separately to see if one engine is still acting wonky? I think I read that you have to keep your speed down when running on one engine. I'm sure someone will chime in with better advice.
Good luck

I would start both and leave the one engine idle while testing the other. This way you shouldn't run into any issues of ingesting water into an engine.

 

[Julian]

Agree....sounds like cavitation. Check for

1. weeds wrapped around the impeller (or anything for that matter around the impeller shaft).
2. Check the impellers for damage
3. Check the clearance between the impeller and the wear ring. If I recall, clearance should be 0.35–0.45mm with a service limit of 0.6mm.

 

[212s]

I concur with the others, this sounds like a cavitation issue. I had a thick weed get wrapped around the impeller shaft of one engine, and it severely impacted performance and acceleration, and vibration. Could be you lost some sealant in the pump and you're now sucking air into the jet intake area?

 

[dwall2181]

Thanks so much for the comments. These feel like the issue. I visually inspected/cleaned out the impeller shaft from the back deck and looking over/into the jet unit from the bottom of the boat and from the rear and don't see anything lodged into the shafts on either side.

At this point, do I need to take off the jet pump housing to get to the wear ring or can I inspect that without pulling the jet unit apart?

Not sure where to find that piece?

Thanks a lot!

I concur with the others, this sounds like a cavitation issue. I had a thick weed get wrapped around the impeller shaft of one engine, and it severely impacted performance and acceleration, and vibration. Could be you lost some sealant in the pump and you're now sucking air into the jet intake area?

 

[FLJetBoater]

Thanks so much for the comments. These feel like the issue. I visually inspected/cleaned out the impeller shaft from the back deck and looking over/into the jet unit from the bottom of the boat and from the rear and don't see anything lodged into the shafts on either side.

At this point, do I need to take off the jet pump housing to get to the wear ring or can I inspect that without pulling the jet unit apart?

Not sure where to find that piece?

Thanks a lot!

Did you ever get to the bottom of this? If not, I would pull the pump for good measure. It's only 4 big bolts, plus the bucket clip and steering bolt. Once you've done it a couple of times it's a really quick process.

 

[dwall2181]

Thanks to everyone for the replies. It seems like the cleanouts were a little loose which I believe could be causing the issue. I used the repair kit to replace hoping it forms a better seal. Will let everyone know how it works out this year.

 

[dwall2181]

Hi All, New year and seem to be having the same issue after putting on new cleanout plugs. Took the boat out for the first time and still having the acceleration problem.

I singled it out and it's definitely coming from the right jet pump.

When I hit the gas, I get rpm's high with very little thrust then eventually the pressure builds up (don't know if that makes sense?) the rpm's settle down and I get thrust after which I have full thrust until I slow down again. There is definitely nothing stuck in the impeller (weeds, sticks, etc.) or cleanout ports...

I'm ready to pull the pump assembly, but....

Should I replace the wear ring or impeller or both?

Any other advice how to troubleshoot the impeller/wear ring to single out which one is causing this issue?

Thanks for your feedback!