Porpusing please help

[Clean 502]

i have a 1999 21' cheetah jet. it has a legend jet with a hydrolic place diverter. i am having problems with the boat porpusing at cruising speeds. i was told i could put cavitation plates on to help. would this be a good idea or should i put hydrolic trim tabs on? would a ride plate help or make it worse? i need some help with this as i am stumped on what to do. i have the money for trim tabs but do i need them. the boat has a closed bow and i talked to cheetah and they said they only made 4 of this style of boat. it has a pretty good size v to the haul. so could anybody give me some advice on what i should do. thanks

[victorfb]

what changes did you make? im assuming you didnt have this problem before. or is this a new to you boat? you should be able to control it with the diverter. trim tabs can help, and also if you just installed a drrop you may have the thrust line too low and need to raise it with a wedge. we need more info on your complete set up to start with.

[malcolm]

I know all boats are different, but the guys that I've talked to with the trim tabs really like them.

[FILUCKY]

I ride plate is a must in setting up your boat when you start modify it.

[SmokinLowriderSS]

I'm with FILUCKY. IMO every jet boat needs a ride-plate. You can adjust it to reduce cruise porposing as well as set the hull attitude under flat-out conditions. Go with the ride-plate.

[MikeF]

The hull is trying to climb onto the top of the water and there is too much weight to keep it there.
Likely best option is to go w/ the trim tabs.
The ride plate is ALOT of work and might not fix your problem. Mohavekid put on a ride plate and still has porposing issues the were thought to have been cleared up by the ride plate when he put it on.

[*BN*]

Maybe the LONG droop snoot could help here.

[BigDoug]

You talked it over with cheetah and they said they only made 4 of these boats ?..............Well there you have it...it wasn't good enough for them to consider making more cause there could be a flaw in the design hence the porpussing (sp) or other issues ? i know i haven't helped you any but you might want to reconsider if this is a safe hull ?.. :boxed:

[Squirtin Thunder]

i have a 1999 21' cheetah jet. it has a legend jet with a hydrolic place diverter. i am having problems with the boat porpusing at cruising speeds. i was told i could put cavitation plates on to help. would this be a good idea or should i put hydrolic trim tabs on? would a ride plate help or make it worse? i need some help with this as i am stumped on what to do. i have the money for trim tabs but do i need them. the boat has a closed bow and i talked to cheetah and they said they only made 4 of this style of boat. it has a pretty good size v to the haul. so could anybody give me some advice on what i should do. thanks
When you are at WOT does it still porpise ???
If so I would say we need to adjust your boat and jet.
If not put the diverter all the way down and cruise.
There is a ton of stuff that we could through at it and will help.
Don't give up !!!! You can call me and I will try and help.

[Hotrodnobody]

Throw a couple of 50lbs. sand bags in the nose and see if it a balance problem. How many lifting stakes does it have? What degree is the intake set at? How big is the rocker in it right about the rear seat piont? Lots of stuff it could be. Trim tabs is a quick fix to a problem that will never go away. Tabs will lower the nose at cruising speeds and scubb off a ton of speed. How wet does the boat ride? IMO you dont need a ride plate if you are under 60-65 MPH in a boat that size.
HRN

[Mohavekid]

Yep, I have the same issue.
I believe it to be a center of gravity problem as my mid randge porpoise gets much worse with a full fuel load and or a lot of passengers.
I tried an extended ride plate without success. Adding weight up front helps, but I'm sure you don't want to ride around with a couple of hundred pounds of sand in your bow.
Since the problem is not static, I am convinced the solution must by dynamic or adjustable. A set of driver adjustable trim tabs with sufficient surface area should do the job.
Good Luck.

[Clean 502]

what changes did you make? im assuming you didnt have this problem before. or is this a new to you boat? you should be able to control it with the diverter. trim tabs can help, and also if you just installed a drrop you may have the thrust line too low and need to raise it with a wedge. we need more info on your complete set up to start with.
the pump is offset maybe 4'' to 6'' and doesnt have a droop. i just recently purchased the boat. when i test drove it the water was flat and i didnt notice the porpusing. the hual doesnt have a hook in it but has a step. i was told by a guy who specializes in jets that it has a slight rocker in the hual. he suggested i put cavitation plates on it. i would rather be able to adjust them while i am under way. at WOT it is fine only at lower speeds with the place diverter all the way down. it gets the porpuse. it runs about 65mph. would a loader great help me at all.

[Mohavekid]

What model pump do you have?
Is it an 'E" or a set back "g' style? Is the motor moved back too?
Your problem sounds identical to mine. Some guys say a loader grate will help, but I'm not convinced.
I think trim tabs or a v-drive type adjustable cavitation plate set up (for the cool factor) is the way to resolve the issue. Glennwood has some cavitation plate kits that you may look into.

[Clean 502]

What model pump do you have?
Is it an 'E" or a set back "g' style? Is the motor moved back too?
Your problem sounds identical to mine. Some guys say a loader grate will help, but I'm not convinced.
I think trim tabs or a v-drive type adjustable cavitation plate set up (for the cool factor) is the way to resolve the issue. Glennwood has some cavitation plate kits that you may look into.
It is the G style set back. and i was told the motor was set back as well. i have looked into the cavitation plates and trim tabs but i am not sure what to go with. i would rather have hydrolic adjustable tabs but they are more expensive then cavitation plates. should i try a laoder intake and ride plate first?

[AZKC]

I have the same problem in my 20ftr. I've been looking at trim tabs, but I'm leaning towards the Lenco electric style. No hydraulic stuff to mess with :idea:

[Clean 502]

I have the same problem in my 20ftr. I've been looking at trim tabs, but I'm leaning towards the Lenco electric style. No hydraulic stuff to mess with :idea:
I have looked at the lenco and bennette but they have a fiberglass/plastic ram and the max speed rating is 60mph. Dana marine makes billet aluminum but they are more expensive. i dont want to spend $600 on some plastic ones that might possibly break. the Dana tabs cost about $900 and can handle high speeds.