Intake grate & Ride plate smooth water porpoising

[Gski251]

I added a Pro-tec intake grate and +60mm extended ride plate to my stock '99 Superjet. First ride was early morning glass water and it was porpoising so bad that I couldn't get up to speed. Later when the water was choppy the ski performed much better. Can anyone give me input as to what is responsible for these ride characteristics? I should have tested one part at a time to learn the different characteristics of each but I live an hour from the lake and was anxious to try them both, not knowing when I could make it out next. Also, the bolts on the ride plate are more exposed than with the stock, sticking out just a hair when looking down the bottom of the hull. Does this affect anything? Thanks

 

[yamanube]

How long have you been riding?

 

[Mike W]

Try shifting your weight forward in the tray. That will help a lot with the porpoising. The bolts sticking down doesn't effect anything.

 

[Gski251]

How long have you been riding?

Only 3 months.

Try shifting your weight forward in the tray. That will help a lot with the porpoising. The bolts sticking down doesn't effect anything.

I tried shifting weight around and throttle control but I will definitively try again. It seemed like no matter where I was in the tray, it would pop out of the water and then get pulled back in. Again, this was only in smooth water. When it was choppy the ski performed as expected. Next trip I was going to try putting the stock plate back on and see how it performs with just the grate.

 

[FX1 696]

Just keep the aftermarket grate and ride plate on there, that's not your issue and they're better than stock. It just takes more practice, you'll get it

 

[yamanube]

This^ ride more

 

[Th3 VVay]

I'm interested to see what you find out here. I also have the protec scoop grate and I even added their +90mm ride plate and I experience the exact same issue. In glass it porpoises a lot, but in chop it seems to ride much better. It also seems to go away if I do wide swooping carves as opposed to going completely straight. I've been riding for 4 years so I don't think its just tray time. I have been able to eliminate 50% of it by getting better at riding. But like you said, if the lake is glassy, there's almost nothing I can do to stop it other than back off the throttle. I'm starting to think its one of two things

1) This scoop grate design is too aggressive and pulls the hull too deep into the water then it pops back up repeatedly. Hence why the porpoising clears up in chop as the grate is not constantly in contact with the water all the time, so its not able to pull the hull into the water as much.

or

2) The foam in the rear of this 1990 hull is waterlogged as sh*t. However I've noticed that the porpoising seems to decrease when I am low on fuel. Which means it likes for the front to be light and in that case I would think the waterlogged foam would be helping.

 

[Gski251]

I'm interested to see what you find out here. I also have the protec scoop grate and I even added their +90mm ride plate and I experience the exact same issue. In glass it porpoises a lot, but in chop it seems to ride much better. It also seems to go away if I do wide swooping carves as opposed to going completely straight. I've been riding for 4 years so I don't think its just tray time. I have been able to eliminate 50% of it by getting better at riding. But like you said, if the lake is glassy, there's almost nothing I can do to stop it other than back off the throttle. I'm starting to think its one of two things

1) This scoop grate design is too aggressive and pulls the hull too deep into the water then it pops back up repeatedly. Hence why the porpoising clears up in chop as the grate is not constantly in contact with the water all the time, so its not able to pull the hull into the water as much.

or

2) The foam in the rear of this 1990 hull is waterlogged as sh*t. However I've noticed that the porpoising seems to decrease when I am low on fuel. Which means it likes for the front to be light and in that case I would think the waterlogged foam would be helping.

It's unfortunate to hear you are experiencing the same issue but glad I am not the only one. Have you had the chance to remove one or the other? This will be my next move.

The standup is new to me but I have years of experience on the water and understand the importance of weight distribution on a boat. I went out again last weekend and played around with body positioning but there is no position that will fully eliminate the severe porpoising on glass. Might just have to accept that this set up does not work well for glass conditions. I mostly wanted to verify that I didn't overlook something or make a mistake during install.

 

[FX1 696]

I don't think any standup I've ever ridden was completely smooth on flat water. Most of it is just learning how to ride to avoid the issue. My feet are positioned left foot forward, and my upper body moves around. When I go from slow to full throttle, I bend my knees and kinda pull my chest closer to the bars. You've just gotta play with it and figure out what works for you. Standups aren't meant to cruise at 20mph in a straight line on glass anyway. Find some boat waves, do some bunny hops, practice your turning skills, tail stands, submarines, etc... that's what standups are all about.

 

[Th3 VVay]

It's unfortunate to hear you are experiencing the same issue but glad I am not the only one. Have you had the chance to remove one or the other? This will be my next move.

The standup is new to me but I have years of experience on the water and understand the importance of weight distribution on a boat. I went out again last weekend and played around with body positioning but there is no position that will fully eliminate the severe porpoising on glass. Might just have to accept that this set up does not work well for glass conditions. I mostly wanted to verify that I didn't overlook something or make a mistake during install.

I don't have a stock grate or another to try so no I haven't tried another. I've just learned to reduce it through body position, and my body weight distribution.

 

[Th3 VVay]

I don't think any standup I've ever ridden was completely smooth on flat water. Most of it is just learning how to ride to avoid the issue. My feet are positioned left foot forward, and my upper body moves around. When I go from slow to full throttle, I bend my knees and kinda pull my chest closer to the bars. You've just gotta play with it and figure out what works for you. Standups aren't meant to cruise at 20mph in a straight line on glass anyway. Find some boat waves, do some bunny hops, practice your turning skills, tail stands, submarines, etc... that's what standups are all about.

I've done a lot of what you've mentioned and it has reduced proposing quite a bit in my time riding. I would say 50 percent has been reduced by learning to ride correctly. And I agree these skis are more fun for doing tricks than riding at full speed, that's why I have really tried to fix the issue in the 4 years I've owned it.

However I would have to disagree that these skis can't ride full out without porpoising. My buddies 650sx cruises flat at wot on glass. Not too mention there are plenty of videos of stock superjets running flat out on glass and not porpoising.

 

[FX1 696]

I've done a lot of what you've mentioned and it has reduced proposing quite a bit in my time riding. I would say 50 percent has been reduced by learning to ride correctly. And I agree these skis are more fun for doing tricks than riding at full speed, that's why I have really tried to fix the issue in the 4 years I've owned it.

However I would have to disagree that these skis can't ride full out without porpoising. My buddies 650sx cruises flat at wot on glass. Not too mention there are plenty of videos of stock superjets running flat out on glass and not porpoising.

I can get my superjet and Fx1 to ride flat at WOT. It's just at lesser speeds (20-30mph) they want to porpoise. That's when I distract myself by turning or going to chase a boat. Kawis are much better with cornering and flatwater riding in general. All the vintage race footage was JS, and in today's age it's the sxr.