Super Jet Why is my Built Superjet so slow!!!

[Yamaha8985]

When I first got my superjet, I thought it ripped pretty good. Runs good, doesn't bog, no issues. Then Someone I knew bought a brand new stock SJ, I took it for a ride and it pulled harder and was faster top end than mine! I have a 760 with heavy porting, Cool girdled head, dual 44 buckshot carbs, speedwerx race pipe, and an msd enhancer. My compression is about 150psi in both cylinders. Why is my setup slower than a stock SJ! Just needs to be tuned better? Are those buckshot carbs junk? I need some help on what to do. I'm thinking about just starting over with a new 701 62t engine and go from there. I appreciate any input.

 

[Fro Diesel]

Taller exhuast ports on your motor. The 61x cyl is better for low end. You could put a different top end on ur ski.

The way a ski hits in the whole package. What prop are you running?
Depending on elevation you could bump compression.
It sounds like you have an old race boat. Creates lots oh powa...just at a different rpm

sent from Fro Diesel using tapatalk2

 

[Matt_E]

You're running a 760 cylinder with 150 psi compression, a dry pipe, and Buckshot carbs. That is a bad combination for bottom end, especially compared against a new Superjet with better port timings and higher compression.

 

[Yamaha8985]

What do think is they best way to get some bottom end..... somewhat saving some of my setup. Im think of dumping the buckshots and putting some stock mikunis back on, ported 61x cylinder and higher compression head. Think that would be a better setup?? I also couldn't tell you exactly what prop is on there. I was told a Solas but that's about it

 

[Matt_E]

I think your cylinder might be fine. I would increase compression to 170-175 psi, put different carbs on it, advance the timing a little bit if it isn't already, and find out what impeller you have.
A B-Pipe with limited chamber might make a difference in bottom end power, but would likely not be as strong as your current pipe in the mid to top.
Definitely check the impeller. The engine could be severely overloaded if it's too steep of a pitch.

 

[oxnard111]

I think your cylinder might be fine. I would increase compression to 170-175 psi, put different carbs on it, advance the timing a little bit if it isn't already, and find out what impeller you have.
A B-Pipe with limited chamber might make a difference in bottom end power, but would likely not be as strong as your current pipe in the mid to top.
Definitely check the impeller. The engine could be severely overloaded if it's too steep of a pitch.

What he said

 

[Yamaha8985]

I think your cylinder might be fine. I would increase compression to 170-175 psi, put different carbs on it, advance the timing a little bit if it isn't already, and find out what impeller you have.
A B-Pipe with limited chamber might make a difference in bottom end power, but would likely not be as strong as your current pipe in the mid to top.
Definitely check the impeller. The engine could be severely overloaded if it's too steep of a pitch.

Alright I think i will try that. I was leaning toward buckshot carbs, you think those would work well with my setup?

 

[Matt_E]

You have BuckShot carbs now.

No, I don't think those would be/are a good choice.

 

[Big Kahuna]

If the ski is set up for racing the Buckshots are fine. But you need more compression and they are a bitch to tune.

 

[Yamaha8985]

You have BuckShot carbs now.

No, I don't think those would be/are a good choice.

Sorry I ment to say "Blackjack carbs" and typed buckshot...typo. Everything I see says buckshot carbs are junk. Im getting rid of those for sure. I don't want to race. I freestyle way more than I race.

 

[Matt_E]

BlackJacks are great.

 

[Scraggly]

buckshots are ok if you keep it pinned all the time lol
down low they are a pain

 

[kevbo]

When I first got my superjet, I thought it ripped pretty good. Runs good, doesn't bog, no issues. Then Someone I knew bought a brand new stock SJ, I took it for a ride and it pulled harder and was faster top end than mine! I have a 760 with heavy porting, Cool girdled head, dual 44 buckshot carbs, speedwerx race pipe, and an msd enhancer. My compression is about 150psi in both cylinders. Why is my setup slower than a stock SJ! Just needs to be tuned better? Are those buckshot carbs junk? I need some help on what to do. I'm thinking about just starting over with a new 701 62t engine and go from there. I appreciate any input.

There are too many possible causes, find a local tuner for help. A small exhaust leak can cause your problem.

 

[Yamaha8985]

I'm going to get some smaller domes for my head, put on some blackjacks with some help from the guys from jetworks and try to get that baby dialed in, and get a prop that will help down low. Hopefully that helps bring her back to life a little. I know im not getting this engines full potential.

 

[d_moss]

i took off a 14/18 solas straight blade prop and put on an 08 super jet stock prop and it made quite a difference.

is your prop bent? is your wear ring in good condition?

On my modded ski I went from a 14.5/18 solas to a 9/15 hooker didnt lose any topspeed and gained lots of low end.

 

[BombThreat]

I would check your prop man. Even with what everyone says about the old race parts and port timing, if what your saying the boat has is accurate you should smoke the stocker. You have a ported 760 with a nasty pipe and big carbs?! That thing should be doing 52-54mph

We have a SN with a 61x 701 with only a redpipe and a blaster prop doing 50 mph... Not even a high compression head b/c we want to run 87 fuel. Your boats got tuning issues. Look at the prop, water routing is big too.

 

[fast superjet chase]

i run 760's in my skis they are all arm jerkers even off the bottom i'd go with a different prop.

 

[mthomps]

Figure out the deal with your prop before anything. Probably a pain in the ass to get them both off and switched but maybe see if your buddy will swap for a ride? Ain't getting no where if your prop is just straining the engine out.

 

[OCD Solutions]

I have the same experience and laugh whenever I hear that race engines don't have any bottom end. My ported 760 has tons of bottom end. It also has 35cc domes, 185lbs of compression and a well tuned B-pipe. It also has a 140mm mag pump but it ran just as strong with the stock pump with a 10/16 Hooker and stubby cone.

 

[Yamaha8985]

Well I took apart my pump. The prop looked good, it's a solas 14.7-18.5. I dont know if that a good prop or not. Here are some pics