Max speed 38 mph, cavitation?

[Wseadoo180]

Hello everyone,

I got a 2006 4tec Sportster 2 months ago, after trying it once and noticing a low top speed, I took 2 months and worked on everything...finally took it out for a day ride! However, top speed at most is still around 38 mph (GPS). It takes off right away from idle ... so I am not sure if its cavitation or not. The prop and wear ring look great to me - I did notice sometimes at idle (lowest speed) - the prop feels a bit rough in the water as if it is loose and rattling

Here is what I did in the two months:

• Upholstery (took the most time, hopefully never again!)
• Oil change, new filter, o rings
• New gas filters (small and big)
• siphoned old gas, new 91 oct gas
• New spark plugs (dielectric grease on the ceramic and rubber)
• New battery, cleaned terminals etc
• Various little fixes throughout

Any suggestions?

 

[Wseadoo180]

Update:

After reading the forums, a common problem is something stuck behind the impeller - I just checked with a scope camera and unfortunately that is not what I have... Was hoping for an easy fix, not this time! :facepalm:

 

[pvamax]

155 or 215 motor? What rpm are you spinning while at 38mph?

 

[Wseadoo180]

155 or 215 motor? What rpm are you spinning while at 38mph?

I will take note of it next time I'm on the water.... Hopefully later today. From what I recall close to 7000.

I may have solved the problem...

First I checked the throttle cable, and that was at the right tension
Then checked every single tube, valve etc... All was good.
Finally decided to take out the air filter box to see if anything needed to be cleaned... Was suprised with two big cracks of which one piece was stuck on the grate, eliminating 40% of the vent area.

Cleaned it, superglued the cracks, cut a piece of 1/8th abs sheet and fixed it on with marine caulking. Will report back if this fixed it!

Thankfully this had the recall done and the vent grate added, otherwise this plastic would have been in my engine!

 

[Wseadoo180]

155 or 215 motor? What rpm are you spinning while at 38mph?

Unfortunately that did not solve the problem
Max speed was 39, for a second it hit 40 - perfect calm water, no wind.
Max RPMs were around 6900 - 7000

I am reading conflicting reports re RPMs - some state 50 mph at 6800 rpms, some state the max rpm should be 7650 ... some even mentioned theirs going up to 8000...

Any suggestions?

 

[Lumps]

the absolute RPMs is not really important. what people are trying to determine: is the engine not strong enough to get to full speed or is the engine at full speed and the efficiency of the pump is no enough to propel the boat at top speed. it is sounding like your engine is getting to top speed (sorry I don't know what your engine red lines at, correct me if I am wrong). that leaves the most likely cause as your prop/rings (unless there is some other drag slowing you down)

 

[C9R0J0]

I see from the pic of the airbox your boat has the 155HP engine. From the maintenance manual 7650 is your max limited rpm. I found 2 tests with your boat, one stating 50mph at 6800, the other 47mph at 7300. Do you know if the impeller is stock?

 

[Wseadoo180]

I see from the pic of the airbox your boat has the 155HP engine. From the maintenance manual 7650 is your max limited rpm. I found 2 tests with your boat, one stating 50mph at 6800, the other 47mph at 7300. Do you know if the impeller is stock?

Yes, sorry I forgot to mention it is a 155 hp.
Where did you find these tests? This is where things are a bit confusing - one is 500 rpms slower but 3 mph faster.

It looks like stock impeller - wear ring and impeller both look like they are in a great shape!

 

[C9R0J0]

Yes, sorry I forgot to mention it is a 155 hp.
Where did you find these tests? This is where things are a bit confusing - one is 500 rpms slower but 3 mph faster.

It looks like stock impeller - wear ring and impeller both look like they are in a great shape!

I believe these are the two that I seen yesterday. I agree the numbers don't make sense, unless they changed impellers from one year to the next.


http://www.boats.com/reviews/performance-test-sea-doo-sportster-8212-let-the-sunshine-in/#.WWPJH4jyvIU

http://www.boatingmag.com/boats/sea-doo-sportster-4-tec

 

[Wseadoo180]

I believe these are the two that I seen yesterday. I agree the numbers don't make sense, unless they changed impellers from one year to the next.


http://www.boats.com/reviews/performance-test-sea-doo-sportster-8212-let-the-sunshine-in/#.WWPJH4jyvIU

http://www.boatingmag.com/boats/sea-doo-sportster-4-tec

Sorry for the delay
I checked the impeller and from what I can tell it is OEM

I also got to sanding down some of the small gel coat repairs I did on the hull, waxing etc, although it maybe negligible friction, I figure I'd give it a shot.
Day on the water yesterday, still similar results

At half way throttle, I am doing around 30 - 35 mph. The next full half movement to WOT, I only get a boost of 4 - 5 mph. Yesterday the water was crystal clear, almost no wind, despite that I still maxed out at 39

 

[Lumps]

one thing I forgot to mention. I cant remember if it effects the new boats. but the 2 strokes had the problem that if the ride plate (maybe elsewhere?) wasn't sealed properly they could let air enter the pump. this would cause cavitation and poor performance. so if your engine is hitting the redline and your rings have the right tolerance and the prop is not damaged, then maybe this is effecting you?

you should do a search to see how to determine this. maybe its not a factor on your style of boat?

 

[Lumps]

ok just a thought. when you are in forward, is your reverse bucket fully clear of your jet?

 

[Wseadoo180]

ok just a thought. when you are in forward, is your reverse bucket fully clear of your jet?

Yup, first thing I checked and was hoping for - but unfortunately no it's fine

one thing I forgot to mention. I cant remember if it effects the new boats. but the 2 strokes had the problem that if the ride plate (maybe elsewhere?) wasn't sealed properly they could let air enter the pump. this would cause cavitation and poor performance. so if your engine is hitting the redline and your rings have the right tolerance and the prop is not damaged, then maybe this is effecting you?

you should do a search to see how to determine this. maybe its not a factor on your style of boat?

I will look into this! Although I am starting to lean more and more away from cavitation since it takes off relatively quick. Will keep you posted. Thank you for the suggestions!!!

 

[Wseadoo180]

Here are photos of the impeller and wear ring I took with a scope camera - Wear ring is probably not OEM? based on the colour. I will try to take better photos with my DSLR tomorrow

 

[Lumps]

ok so that looks pretty clean. nothing on my boat looks that new. are you able to get a shot of where they stamp the prop specs on the impeller? maybe the previous owner replaced it with one different spec?

 

[Wseadoo180]

ok so that looks pretty clean. nothing on my boat looks that new. are you able to get a shot of where they stamp the prop specs on the impeller? maybe the previous owner replaced it with one different spec?

I managed to get some photos with the scope camera - there is a ripped barcode on the prop, not sure if this may help

I also noticed some rust on the drive shaft - is this typically ok?

 

[Lumps]

I looked the part number for the prop that should be on your boat and it showed as 267000673. From you shots it looks like that's what your label is saying

It can't be making your boat faster having that label there but I can't imagine that's what is causing your trouble

 

[pvamax]

Update:

After reading the forums, a common problem is something stuck behind the impeller - I just checked with a scope camera and unfortunately that is not what I have... Was hoping for an easy fix, not this time! :facepalm:

What elevation are you at?

 

[Wseadoo180]

What elevation are you at?

Sorry for the delayed response - two different lakes, one at 70 meters, the other 400 meters

 

[pete63]

sorry just skipped read the thread....
change the wear ring, remove the pump check for for sticks inside service the bearing and change the ring. it will stop the guessing game and rule out or solve the issue.

 

[Wseadoo180]

sorry just skipped read the thread....
change the wear ring, remove the pump check for for sticks inside service the bearing and change the ring. it will stop the guessing game and rule out or solve the issue.

Hello Pete,

Yup that is what I had decided to do - I will be first changing the wear ring, and getting a new neoprene seal
I was looking at my old Speedster that I sold to a friend over the weekend, and my wear rings on it look much smoother than this one, although I used it alot. although this has very small scratches on it, I am hoping it is the culprit

 

[Wseadoo180]

sorry just skipped read the thread....
change the wear ring, remove the pump check for for sticks inside service the bearing and change the ring. it will stop the guessing game and rule out or solve the issue.

Yesterday I took everything apart - things looked in perfect condition to me except for the neoprene seal (had cracks in it, however silicone was also used).
This morning I took everything to the dealer...even the dealer argued against a wear ring as both the wear ring and prop look brand new they said.
They checked everything and it all looked good to them...even the mechanics were puzzled.

I replaced the seal, put everything back together, going to wait 24 hours and try it tomorrow in the water.

 

[pete63]

the carbon seal is usually the other culprit in cavitation. the best thing is to read the forums on the carbon seal and investigate if there is still cavitation.
cavitation is simply the water flow though the pump being disrupted either by air (being sucked into the water flow though the pump) or the water flow being altered (foreign object or damaged or worn part).

 

[Wseadoo180]

Well I am not sure what to do next...

3 weeks ago I took the whole jet assembly apart and went to the dealership.
Dealership agreed that it looks like a brand new prop and wear ring were installed.

The only thing that didn't look good was the neoprene seal - it was in rough shape and alot of silicone was used there. I cleaned it all up, greased, resealed, gasketed all required areas, and changed cone grease.

Today was finally the day the lake was calm enough that I can try to hit max speed and measure it on my GPS.
Same problem.... max speed is still 39 mph (hit 40 for a second).

at less than 50% throttle I am doing 5500 RPMs and cruising at 30 mph.
At full 60% to 100 % throttle, I am doing 6800/900 RPMs and getting 39 mph.

 

[Lumps]

Do the 4tec engines need to have the ride plate sealed? Maybe yours is leaky?