96 Speedster cavitation -update-

[Whister]

Here's the original thread from last week.

http://seadooforum.com/showthread.php?t=4256

What I've been up to-

I repaired the damage in the channel before the impeller on the right side. I did this with some epoxy and smoothed it out to make the surface flow correctly again. I didn't repaint in there because I don't really care what it looks like, as long as it doesn't leak ( it doesn't)and performs like it should.

I tore down the jets on both engines. The right side had no seal on it, the left side did. I installed new seals on both jets.

While I was in there, I figured it was a good time for new impellers. I used the Skat Trak 14.5/22.5s with new grommets.

The wear rings were recently replaced on the boat, and the new impellers were a scrape-to-fit clearance on them. The gap is now limited to the runout on the prop bearings (not much)

All this, plus I greased everything, lubed all the cables and adjusted them to ensure that the reverse hoods were fully locked up when in forward.

It still cavitates.

Not too bad... the improvement was dramatic, but it still requires easing into the throttle slowly to gain speed, and takes mabye 10 seconds or so to get up on plane, then it takes off. The problem is much worse with more passengers in the boat. We went out today with four of us and a labrador retriever, and it still cavitated fairly bad. We dropped two passengers and the dog off at the sand bar and took the boat back out and it was much improved.

I guess my problem lies in that I don't know what tio expect from it. I've never had a jet boat before, never even ridden in anoither one, so I don't know what it should be like if it were 100%. I've had an XP800 before and ridden lots of other skis... I'm expecting this boat to holeshot like a jetski. Is that possible?

 

[robin savell lloyd]

A hole shot like a jet ski? I would not think so but maybe close. I would think that it should be a little beter than it is. I had the same problem you you are having when I first bought mine. I had never riden in one like mine so I had no idea how well it should take off. I had just got threw making many other diferent repairs to my boat. The cavitation was the last problem on my list and did not want to play around with it as I was allready sick and tired of working on this boat part time for 5 months and not having fun, So I bought every thing possible to make all wear parts that cause cavitation new. I allso included the best hole shot impeller that money could buy [solas concord] I allso resealed the ride shoe and the intake grate to the botom of the boat. I am sure that my boat is very close to how it should be now. I have only one engine in my boat same jet pump as yours and I can have 650 lbs of people in the back three seats and still come up on plain in about 5 seconds about 15-20 mph. Resealing ride plate should probly be the last thing you try as you can cause damage as I did on my first one, It allso takes along time to get the parts clean enough to seal them back on. you may need to use heat to break the sillacone bond or you will end up breaking a part as I did and that may become the bigest time consuming repair that you may ever take on. It was a nightmare for me. :cheers:

 

[tawood]

Cavatating or just slow up on plane?

I've had jetskis and a jet boat, and neither, no matter how much weight was in/on them, would cavitate if everything was working okay....now, the boat does accelerate more slowly due to weight, but it does not cavitate from weight....only from problems with the jet drive.

 

[unclejay]

Not Cavitation

I am thinking you dont really have cavitation, but an intrenal engine problem like low compression.

Cavitation makes a distinctive sound, the engine revs increase faster than the throttle movement would seem to dictate, like when you jump a wave and the engine screams.. only to a lesser degree. There is a definite hollow sound.

if your engines make a deep, throaty normal sound while accelerating, and rev up smoothly, but just dont seem to have any 'oomph', that would more likely be compression, carb tuning, bad spark plugs etc.

My 95 Speedster (13 years old) still has plenty of snap, takes about 8-10 seconds to plane at full power, and accelerates like a bandit. However when the tiniest object jams the pump, I get the dreaded cavitation sound and immediate loss of oomph.. even though the revs stay up or increase.

 

[Whister]

It's cavitating for sure. When full throttle is applied from a stand still (or half throttle for that matter) the RPMs surge like a car that broke a driveshaft. When you ease into it everything works fine.

Once it's up on a plane it's pretty quick for what it is. It's just a dog at low speeds.

 

[robin savell lloyd]

I may be wrong but looking at photos in your other post it looks like you still have broken parts of your drive shaft shields. [the part that is supose to help keep ropes from being rapped around drive shaft.] I have read that when these break that they cause bad cavitation. You maybe able to remove them all to gether or cut them flush so they do not airiate the water going into pump. The drive shafts allso look rusted I would try and smooth them down a bit with sand paper. Good luck and I will keep looking into this for you. :cheers:

 

[robin savell lloyd]

Resealing the ride shoe

Resealing the ride shoe. This would be the last thing I would do if my boat had a cavitation problem. I have read by many pros and ametures that this did fix their cavitation problem after replacing every thing else with new parts they found that their ride shoes did not have a good seal. I did this to my boat as every thing looked good to me and I did not want to have any more problems. I also replaced every thing else that looked ok to me as I was ready to start haveing fun and did not want to be working on this boat any more. new wear ring, impeller, and threw hull seal.. I do not know what made the bigest difference. but it is fixed. Maybe next time I have cavitation problem I will know for sure what the problem is. I do know one thing, It will not be a bad ride shoe seal as I used way more sealant than I probly needed and I believe I bought the best sealent out there it is called RIGHT STUFF I found it at advanced discount auto parts. It comes in a cheese wizz type of can it is pricy about $13.00 a can. I used 2 of them on my single ride shoe. seadoo allso sells the RIGHT STUFF. heat may be required to break bond of the old sealent or you may damage boat and or ride shoe. You may allso need a jack to jack ride shoe off very carefully not to break it. Do not be like me and not use heat at first and crack your ride shoe I know this is for singles but I belive the cavitation part applies to twins allso. This seems to be a need to read thread for all older seadoo 14.5 boats. Hope this helps alot of people out. cavitation, pump shoe, ride plate, mods and ect. http://www.groupk.com/sdjetboats-1.html :cheers:

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