[96Laveycraft21Xt]

Hey there everyone, been scoping around for a while but this is my first post.  I wanted to get some feedback from some great minds here.

My history with Jets ?  My Brother and I have owned a '69 tahiti 18' with 455 olds/berkeley combo for 13 years.  it was our first boat.  3 years ago i upgraded and bought my 96 Lavey Craft 21 XT Ski with a 454 (330hp) and Dominator pump.

[attachimg=1]


Our Tahiti ran on rails with the place diverter, the Lavey, not so much.  Porpoises all the time, at all speeds.  The only real way to stop it is to toss two kids up front and trim all the way down.  not the best for cruising efficiency haha.


About the boat:

transom to nose 21', total overall length with built in swim step 22' 8".  #/- 3300 lbs .  Dominator insert pump and the hull had a delta pad that best i can measure with angle finder is 3* up from keel.


When i bought it, the ride plate (Cav plate? )  its small like 8" x 12", was set 3* down from delta (0* from keel)  i adjusted up 3* so that it was inline with delta pad and no change in porpoising.   This is very annoying as i cant cruise faster than 3800 or even trimming all the way down doesnt work any more and i cant ever throw a roost as i look like a bucking bronco fool on the water 



What are your thoughts?

[96Laveycraft21Xt]

[attachimg=1]

[96Laveycraft21Xt]

[attachimg=1][attachimg=2]

[J2]

Use a straight edge to check for hook. I have a 4ft steel ruler I use. Hold it up against the bottom on both sides of the jet and see if you have a significant gap near the back.

Pics of the jet set up would help. Both sides & back view.

[96Laveycraft21Xt]

Use a straight edge to check for hook. I have a 4ft steel ruler I use. Hold it up against the bottom on both sides of the jet and see if you have a significant gap near the back.

Pics of the jet set up would help. Both sides & back view.

Let me see what pics i have of the pump set up.  I know i have some somewhere from when i shimmed it up...... give me a few.

[96Laveycraft21Xt]

Basic pic of the setup as i bought it.

[attachimg=1]

Here you can Kinda see the delta pad and angle of the ride plat at rest

[attachimg=2]

This is the final spacer set up to get it level to delta

[attachimg=3]

[5150whiteboy]

Tim at place did a drop, ride plate to mine with 4* wedge and problem solved, I have a 1999 team Hawaiian and it was bad prior

Sent from my SM-G955U using SoCal Jet Boats mobile app

[J2]

Does look like thrust height needs to be lower. 5150's post supports that since he has a similar hull. I'm assuming the 4 degree wedge he's talking about is installed in the wedge down position to get the thrust height correct. If 5150 has a pic from the side with a straight edge up against the ride plate this will give you a really good reference point.

Typically the ride plate is set 2 degrees up from bottom of the boat to start. Some hulls like a little more.

Then using a straight edge off the ride plate measure the gap to the bottom pin of your steering nozzle or droop if you have one.

Once you see how big the gap is then you'll have a better idea if a mini droop or full droop would be a better fit.

On a Daytona a gap of 3/4" is what is most written about. I'm guessing you should be at 1" to 1.5".

[96Laveycraft21Xt]

Tim at place did a drop, ride plate to mine with 4* wedge and problem solved, I have a 1999 team Hawaiian and it was bad prior

Sent from my SM-G955U using SoCal Jet Boats mobile app

What length and weight is the hawaiian?  Was that 4* up or down?  what HP or rpms are you turning?  what type of speeds did it porpoise prior?

Thanks!

[96Laveycraft21Xt]

What length and weight is the hawaiian?  Was that 4* up or down?  what HP or rpms are you turning?  what type of speeds did it porpoise prior?

Thanks!

5150, you there?   

[96Laveycraft21Xt]

Ok, well since this thread sort of died, im going to bring it back with a little update.....



I dropped a fresh 454 off to GS marine for my bosses 81 Bahner about a month ago and while i was there i asked Greg about my problem.   Now i am not kidding when i tell you that i didn't even get to finish my first sentence.

Went just like this:


Me: Hey Greg, i have a problem with my boat.  Its a 96 lavey craft 21 Jet ...

Greg:  ....and i bet it porpoises like crazy.......

Me:   

Me: so thats a common thing?





Long story short i guess,  Lavey had a guy setting the jets in those days that was less than knowlagable and was setting them wrong.  They  were just bolting them to the transom BUT with the delta pad being up 3* the shoe of the pump was still level with the keel or down 3*.

Greg said to go home and check.  This is what i found.

[attachimg=1]

[attachimg=2]


So, proposed solution from GS is the shim the bottom of the pump back 1/2" to 5/8" till the shoe sits inline with the delta and re-set the intake to match.


Thoughts?   

[96Laveycraft21Xt]

I never thought to check there cuz, well, i guess i assumed that it would be correct and that it would all be in the ride plate adjustment...

Guess not!

[J2]

Use a straight edge to check for hook. I have a 4ft steel ruler I use. Hold it up against the bottom on both sides of the jet and see if you have a significant gap near the back.

Pics of the jet set up would help. Both sides & back view.

My first thought was hook, which was created when the intake was installed wrong. I didn't describe how to check that very well.

Thanks for the update 

[96Laveycraft21Xt]

My first thought was hook, which was created when the intake was installed wrong. I didn't describe how to check that very well.

Thanks for the update 

No Problem, when i think of hook my first thought was to check the sides that are fiberglass.  never thought to check the shoe but now lookinging at it, the angle looks soooooo obvious....

Now i know why it was so hard to bend the plate up 3* 

[96Laveycraft21Xt]

HEY!! sorry for the "short" hiatus, life's been busy but i have been making good progress on the boat and wanted to update everyone as well as get some further help so bear with me as i work through the updates & pics to where we are today...

[96Laveycraft21Xt]

As i left off before, i spoke with Greg @ GS marine at length about the porpoising problem and took the boat to him.  He made a call to Lavey and had a discussion with them and we decided to "re-set" the pump to the right transom angle to correctly match the delta pad.  After pulling the pump apart and separating it from the fiberglass and setting the angle, we took about a week looking at the intake side of the "suction" and found that it was not going to work to move the pump.  im going to  attempt to draw what the problem was.

The boat has a 12 TD dominator pump which has an intake side like this...
[attach=1]

Basically like a Berkeley E pump for those who are not familiar.

The problem is that as the transom angle changes, so does the roof line of the intake side. To get the 3* out of the shoe the roof would create a "lip" about 3/4" tall and that was going to create a big problem trying to blend that with epoxy.

[attach=2]

[96Laveycraft21Xt]

found some more pictures....


Pump out of the boat.
[attach=1]

The bad lip or flow it would have caused
[attach=2]

another angle

[attach=3]

[96Laveycraft21Xt]

Bad shaft from no rear grease zerk.

[attach=1]

[attach=2]

weird machine ridge/burr

[attach=3]

[96Laveycraft21Xt]

whoever got into this pump before put in a Berkeley impeller, here is how it looked:


[attach=1]

[attach=2]

[attach=3]

[96Laveycraft21Xt]

bowl had a sharp edge so i gave it about a 3/8" to 1/2" radius to it for smoother water flow

[attach=1]

[attach=2]

[attach=3]

[attach=4]

and cleaned up random buggers

[attach=5]

[96Laveycraft21Xt]

we put everything back together and did this instead


[attachimg=1]

[attachimg=2]

[96Laveycraft21Xt]

took it for a test drive and sooo much better with the trim tabs.  took a few adjustments to get full roost without porpoising but i think i have it close...


Had a nice October Storm in Parker 2018

[attachimg=1]

[attachimg=2]

[96Laveycraft21Xt]

still had a slight porpoise so i did some more looking and noticed that my ride plate was bent and i decided to try to adjust it inline with the shoe and straiten it out a bit. was curved front to back and side to side as well.

the front 3rd of the plate is on the level:

[attachimg=1]

the level is on the shoe here:

[attachimg=2]

you can see the side to side curve here:

[attachimg=3]

and on reinstalling, found that the middle screw was sticking up into the intake at least 3/16", so i fixed that...

[attachimg=4]

[96Laveycraft21Xt]

i really like how the boat has been heading in a positive direction with each little change. Depending on fuel and load i can sometimes ride full roost with no porpoise, and with more weight (full 50 gallons fuel, back bench ice chest full, 6 people etc) i can still run up to 75% full up nozzle before porpoise.  I would consider this now problem solved.  What are your thoughts?




here is a decent ride picture:



[attachimg=1]

[96Laveycraft21Xt]

Does look like thrust height needs to be lower. 5150's post supports that since he has a similar hull. I'm assuming the 4 degree wedge he's talking about is installed in the wedge down position to get the thrust height correct. If 5150 has a pic from the side with a straight edge up against the ride plate this will give you a really good reference point.

Typically the ride plate is set 2 degrees up from bottom of the boat to start. Some hulls like a little more.

Then using a straight edge off the ride plate measure the gap to the bottom pin of your steering nozzle or droop if you have one.

Once you see how big the gap is then you'll have a better idea if a mini droop or full droop would be a better fit.

On a Daytona a gap of 3/4" is what is most written about. I'm guessing you should be at 1" to 1.5".

Lets discuss this a bit. i have heard mixed theories on droop snoots, "they are for big boats", "they are for small boats" yada yada yada.  Place diverters website says it works great for bi heavy boats.  is that just because of the drop or is it the 8.5* wedge built into it?

I would like to know more about the theory of  thrust height! i have never heard this discussed before.  Why is 1" to 1.5"  your recommendation? what determines this?  Mine right now is right at 3.5"