Super Jet 1996 Round Nose SuperJet Project

I'm resurrecting my old thread. I can't believe I have had this ski for 8 years now :oops: But, I am back into the tray hauling it all apart again. My reason is that the bottom deck of my tray section has broken open leaving a rather substantial breach on both sides. My thoughts are this happened from the removed original expanding foam leaving the tray area lacking internal structure. The pool noodles will compress a lot and couldn't be jammed in there tight enough to give adequate structure so I will be removing and discarding those. The idea was given to me by Quinc to use rigid foam that can be bought at Home Depot. I went a step further and researched the foam variants because it came to memory that there has been a lot of question on here about what is a good alternative to the expanding foam. I too agree to that, I didn't like the mess of the original stuff when I cleaned it out, and I didn't want to do it again should there be a reason to get back inside the tray section. Having researched foam for a good portion of the last 4 or 5 days, I have found that the most applicable foam for my needs is a high density ground support foam with a compressive strength of 100 psi.

Initially, when researching the different manufacturers and where to get it, I learned that when it is in the form of 7 or 10 inch thickness, it is called dock billet. While this is not widely available for me in my location, what I have found is Dow Highload 100 blue rigid foam intended for use under load bearing surfaces such as airport runways etc. It is closed cell foam with the desired 100 psi compressive strength. It is also regarded as beneficial for use in marine applications where there is a need for structural integrity, and in the right thickness it can be used for artificial islands like docks, golf course islands and the like. The sheet size I bought comes as a 2" thick by 24" wide and 8' length. I will cut it accordingly and laminate it using Lepage PL300 foam board adhesive. This adhesive is specially formulated to bond well to foam and not attack it deteriorating it. I will update with photos later this week.

On a plus side, my original repair job using aluminum threaded backing plates worked to my benefit. I was able to chisel off the old glass repair work...with a good bit of difficulty mind you...and expose the fasteners for re-use on this next repair. I will also be removing the scupper system as I had sealed it off a long time ago due to constantly leaking one way valves and engine compartment flooding. I have gone this long without it, that proves I really do not need it. While I'm at it, I will be removing the Tom21 sponsons I installed years ago because the first 1/4 of the front portion on the left side eventually broke off. I will be turning my hull back into a mostly stock hull and keeping that way. Below are some links to some 100 psi capable foam options.

My Method For Aftermarket Carburetor Air Flow Synchronizing

I put together a quick run down of how I synchronize carbs. It is just a simple explanation of my methods that have given me the best results and worked reliably for me for many years now. So to get onto it...

When setting up aftermarket carbs for air flow the first things I do are to make sure all the hardware settings are the same. All mixing screws are setup to where I would normally start off to get the ski running relatively well, both throttle valves are adjusted to be closed at the same time without the idle screw holding the valves/butterflies open and the flame arrestors are off. Next I get my idle setup to about what I figure is proper, the tach bounces around a little bit so I just try to get a decent on trailer speed set up. When I'm happy with my initial idle speed I set my sync meter up, it gets friction fitted into the carb openings. For the bigger carbs like the Full Spectrum 48s, there is an adapter you can buy for this meter to suit those diameters. This one will go in and just barely fill the void but it's best to get the adapter for a proper seal. I want the full airflow going through the meter only.

With the hardware setup and ready, I check the airflow. The little orange pin will raise up indicating where you're at. The following photos are just to show what I do with a basic understanding of what I look for on a set of aftermarket carbs where the throttle shaft is a little more difficult to work with.

This section is for aftermarket carbs only that require a throttle shaft coupler system not typical to OEM carbs.

In the first photo, I have a description of the only parts I need to pay attention to when doing this. I call the carburetor with the throttle cable carb #1 because it does all the controlling, carb #2 just follows its lead. If I find that for example carb 2 isn't flowing the same amount of air, I shut the ski down and begin either loosening the second carb at the throttle shaft if I can, or I remove the cab setup just enough to get access to the set screws on the throttle shaft coupler. The speed plate is a really nice thing for doing these changes.

Photo 2 shows an example of where the meter typically runs at but not always, it will change with idle speed.
Photo 3 shows a possible scenario where carb 2 has a lower airflow.
Photo 4 - I only loosen the carb 2 side of the throttle shaft coupler as I will be increasing the airflow through that carb to balance with carb 1
Photo 5 - back the idle screw out until it is not putting any pressure on the idle speed set tab. I count how many turns out I go with it too so I can return to my predefined idle speed from before
Photo 6 - I insert a thin 0.002" shim between the valve and carb body as a starting point, this keeps the valve open ever so slightly to increase the airflow hopefully to match the volume being processed through carb 1
Photo 7 - with an eraser on a pencil, I compress the shim to take shape with the bore of the carb
Photo 8 - while holding the valve in place with the pencil I tighten up the throttle shaft set screws
Photo 9 - re-install the carb setup and test again with the flow meter, if the flow hasn't improved enough, I will move up incrementally with the shim thickness until I get as close as possible on a matched air flow
What I am doing here is compensating for any differences in hardware through the throttle valve position to get as equally balanced air flow as possible and it only takes a very very subtle change in that position to make it happen. When it is balanced, both carbs will be pulling the same volume of air through and then the fuel tuning can begin.


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My Method For OEM SBN 38 and SBN 44 Carburetor Air flow Synchronizing

OEM carburetor synchronizing on a Yamaha 62t base is quite possibly the easiest thing a person can do. In the following photos you will see how I do it.

In photo one, I identify the carburetors the same as above, carb #1 has the throttle cable and is the controlling carb, carb #2 is just following its lead.
I make sure that both carbs have the same hardware settings such as both sets of mixing screws are at the same settings according to their circuits, and both throttle valves have been closed at the same time with no idle set screw pressure on the tab. There is a throttle valve sync screw in between the OEM cabs as seen in photo 4. There is actually 2 of these, one is for the chokes, the other for the throttle. I never use the chokes so I remove them and replace with a primer system.
Photo 2 - while the ski is running with a basic setup and generic idle speed setting that I am happy with I friction fit the air flow meter into the carb openings. On OEM 38 and 44 carbs, it will hold in there nice and snug.
Photo 3 - If I get an under performing reading as seen in photo three, I simply tighten down the sync screw very minimally while the motor is still running, remove the screwdriver and allow the motor to settle down. It will raise in idle speed a good bit because you have to put some pressure on the screwdriver to turn that screw. Once I get the flow meter to read the same as carb one that's it, syncing is done. I will double check both carbs after all adjustments too just to be sure both are flowing at equal amounts. So that's it, there's how I have been doing this for a long time now and always had very good results. Thanks for reading.


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My sync tool is this, there are Chinese versions that are terrible, I just stick with the German made one.

A little quick update, the set of aftermarket carbs shown in the above post, I just setup these up this evening for their first time since I have had access to them. I left my good set of shim gauges at home with all the shims down to 0.0005" and only had a 0.006" shim available. I gave it a try just because. I pretty well figured it was too much and sure enough it was, so I decided to look around for something else that would be a decent bit of shim and came up with a piece from an old carb kit as seen in the photo. I had to bring more air into carb 2 to match #1, so as mentioned above, I loosened the throttle shaft coupler screw on carb 2's side, slipped this thin plastic fuel pump diaphragm into the carb bore the same way as the shim gauge would go, I only used a corner of it though to keep it as close to the center of the bore as possible, held the throttle valve tight compressing the plastic, tightened everything back up and fired up the ski. It was exactly the thickness needed and synced the airflow to the same volume throughput of carb 1. Before doing this, the ski was running a little rough, after doing this it smoothed out a nicely and has a clean and consistent idle now. I just wanted to show this because even in a pinch, you can find a shim just about anywhere.


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I'll be slowly updating this post now that things are somewhat settling down around here...for now. But on a quick update as to what has been going on, last year I breached my hull in the tray section. I firmly believe it was because the pool noodle idea although good for its buoyancy, no good for any we're all very aware lol. I had them jammed in there as tight as I could but there's only so much they can do. Because they're not really designed to be strong by any means, I believe my bottom deck buckled from all the harsh pounding causing the breach. It also extended into flex cracking a fair distance under the bond rail. Since I had to start getting rid of paint in preparation for repair work I decided I will go back to a much more visible color on the water and will be returning to the original white but with a new decal package. So the paint removing process begins. In addition, one of my Tom21 sponsons snapped off about the leading 4 inches even with them being screwed, bolted and 3M 5200 glued in place.


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