Issue with porpoising 1990 SJ

I

IceAxe

Location
Anchorage
I understand riding time Will help this issue but I’m curious if there is anything I can upgrade to minimize the porpoise. I have about 30 hours on this beast and can shift my body weight to minimize it, but I cannot go above probably 1/2 to 3/4 throttle without porpoising, starting small then quickly becoming uncontrollable. I’ve read shorting my pole, ride plate, impeller and a few other things may help. Would like some more input before I pull the trigger on anything
 
john zigler

john zigler

Vendor Account
Location
wisconsin
Extended ride plate, and aggressive scoop will help settle it down. As you say, tray time is the real solution.

Also, your foam is probably wet, making the rear of the ski heavier than it should be. Drill a 1/4" hole at the rear, low 3/8 of an inch or so above the bottom. Tilt the ski up and see how much water comes out. You can patch the holes with epoxy. (jb weld, or marine tex is easy to use)
 
OCD Solutions

OCD Solutions

Original, Clean and Dependable Solutions
Location
Rentz, GA
^^ Wet foam was my issue. I did all the above listed mods with minimal effect and then finally bit the bullet and removed 28lbs of water by refoaming.
 
chixwithtrix

chixwithtrix

Addicted
Location
Houston
A coworker has the same issue with his mostly stock square nose, after riding it I told him it needs:

Shortened pole to let you to move your body weight forward.
Wider zero degree bars will allow your elbows to come up, away from your body for a more aggressive stance, control, and lean a bit more forward naturally.
Longer ride plate essentially makes the ski longer. I loved the Pro Watercraft one on my 2014 SJ: https://prowatercraftracing.com/product/hfc-yamaha-superjet-race-plate-96-07/
Intake grate will help keep it stick down and slide less.
 
I

IceAxe

Location
Anchorage
Thanks for the info everyone.

@john zigler Wet foam may be a major factor... however I weigh 225 and could probably lose about 25 lbs so maybe ill just do that instead of ripping the ski apart. Next spring ill drill a hole and see what I find. thanks

@chixwithtrix Im 6ft tall how short would you recommend going with the pole? handlebars at the firewall? shortening the pole is where I'm going to start.
 
OCD Solutions

OCD Solutions

Original, Clean and Dependable Solutions
Location
Rentz, GA
Ha, I was 227 when I started the rebuild of my old SN in the fall and 184 when I finished it in the spring. Between the wet foam and the gym I dropped 71 lbs over the winter and it made a huge difference in my riding.

If you can make the commitment, I highly recommend both courses of action. :cool:
 
Quinc

Quinc

Buy a Superjet
Location
California
IceAxe said:
Thanks for the info everyone.

@john zigler Wet foam may be a major factor... however I weigh 225 and could probably lose about 25 lbs so maybe ill just do that instead of ripping the ski apart. Next spring ill drill a hole and see what I find. thanks

@chixwithtrix Im 6ft tall how short would you recommend going with the pole? handlebars at the firewall? shortening the pole is where I'm going to start.
Click to expand...


I am 6' 220 and went with -8" on the pole with 0 degree bars and it is very comfy. I also cut some off the back of the ski and ride plate. Tray time is only way to get better.
 
I

IceAxe

Location
Anchorage
The OCD Garage said:
Ha, I was 227 when I started the rebuild of my old SN in the fall and 184 when I finished it in the spring. Between the wet foam and the gym I dropped 71 lbs over the winter and it made a huge difference in my riding.

If you can make the commitment, I highly recommend both courses of action. :cool:
Click to expand...

Haha nice work!
 
Vumad

Vumad

Super Hero, with a cape!
Location
St. Pete, FL
Crouch low, hang your ass off the back and pull back on the bars. Loading the nose is like preloading shocks on a dirtbike. It causing you to bounce. Like the rhythm sections, get your weight back and hold it open.

Also, if you have an aluminum prop, get rid of that turd immediately. That cavasaurus wont let you stay hooked up.
 
Pro-pulsion

Pro-pulsion

Location
Ontario, Canada
An easy fix that helped my ski out just enough was to add about 4 stainless washers between the hull and plate at the two rear bolts. It pushes the plate down just enough, some people find the skis has a weird ride to it but I never noticed that. It let me keep the fun of the shorter stock plate while keeping control of the nose. I believe the squares have 6 bolts in the plate no? just make sure to add washers in the middle bolts only to take up the extra airspace, probably only need 1 or 2 at the mid point. I'm not as tall but I do weigh in around the 195 lb mark, no soaked foam in my hull though, I too have been victim of that ordeal :p
 
Sparkplug

Sparkplug

Location
Red Bluff CA
you can ride a superjet with absolutely no ride plate even bolted to the hull, with a stock square pole, stock bars, stock intake grate, and lean all whe way forward, on one foot, and it will not porpoise, at all. Ive done it for miles before.

Anything other than tray time is a band aid, plan and simple. Im shocked how many supposed og riders in this thread are reccomending bogus solutions. Whatever works I guess, some people like the easy way.

Sent from my SM-G930V using Tapatalk
 
I

IceAxe

Location
Anchorage
Sparkplug said:
you can ride a superjet with absolutely no ride plate even bolted to the hull, with a stock square pole, stock bars, stock intake grate, and lean all whe way forward, on one foot, and it will not porpoise, at all. Ive done it for miles before.

Anything other than tray time is a band aid, plan and simple. Im shocked how many supposed og riders in this thread are reccomending bogus solutions. Whatever works I guess, some people like the easy way.

Sent from my SM-G930V using Tapatalk
Click to expand...
Damn. You’re huge.
 
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