rhino jet jon

[ColtonS]

Is this boat a flat bottom?

 

[brianb2247]

It is flatbottom

 

[brianb2247]

one problem im having is 5/8 throttle and up itll run good then20 to 30 seconds it shuts off like the pop off or jets aren't set right but I set it up exactly per the carb rebuild instructions and pop off which is at 21 pounds . I called sbt today the guy said to set it at 38 psi pop off . wonder if this is the problem.

 

[ColtonS]

one problem im having is 5/8 throttle and up itll run good then20 to 30 seconds it shuts off like the pop off or jets aren't set right but I set it up exactly per the carb rebuild instructions and pop off which is at 21 pounds . I called sbt today the guy said to set it at 38 psi pop off . wonder if this is the problem.

How long/hard for it to start back up?

 

[ColtonS]

It is flatbottom

Have you made any mods to reduce cavitation?

 

[brianb2247]

I have welded a 24 x 48 piece of .125 aluminum under boat to make jet housing flush to bottom of boat also I lplugged
A piece of angle aluminum under the boat in the very center 1 1/2" angle alumn. I think it could have been causing cavitation some guys have talked about spooning the bottom but ive looked on line to find nothing.

 

[brianb2247]

When it shuts off I come to a stop engine turns over maybe a sec. And it fires back up

 

[ColtonS]

When it shuts off I come to a stop engine turns over maybe a sec. And it fires back up

Although 38 psi sounds like a little much to me its an easy enough job and I would try it. I had similar problems with my polaris engine and it turned out to be going into a "limp mode" because I removed the oil injection system..... better hope yours is carb related and not electrical [-o<

 

[ColtonS]

I have welded a 24 x 48 piece of .125 aluminum under boat to make jet housing flush to bottom of boat also I lplugged
A piece of angle aluminum under the boat in the very center 1 1/2" angle alumn. I think it could have been causing cavitation some guys have talked about spooning the bottom but ive looked on line to find nothing.

The flat bottom will definitely cavitate in light chop especially if you are running shollow rocky shoals. If you don't plan to run very shallow then the spoon should work fine but if you need something a little more durable I would put a "reverse" or "upside down" tunnel on it.

 

[brianb2247]

reverse tunnel???? any pics . any body done this to theirs

 

[ColtonS]

I don't have any pics of the one that I done but there are a couple boats in the SE Missouri area with them, hopefully they are lingering around on here and will chime in.

I've seen them done 2 different ways but this little sketch pretty much sums up how I made mine a few years ago.
It only needs to sit about an inch under the boat and since its all flat surface you can make it out of thicker material because it doesn't need to be bent/shaped. All it really does is extend the face of the intake below the boat.

 

[CedarRiverScooter]

Colton - On mine, the intake is 2 inches below hull & it still cavitates.

I am going to add a spoon in front of the intake.

I am in the middle of making a 'prototype' out of stacked plywood. I am going to screw & glue it on for evaluation.

If it works, I will make a permanent one out of fiberglass. It will be thru-boilted & sealed with 3M5200.

I am copying the shape of a tablespoon, just magnified about 15X.

 

[brianb2247]

Keep us informed on that spoon feel free to post some pics thanks

 

[Ranchero50]

Mine worked out pretty good.

 

[ColtonS]

Colton - On mine, the intake is 2 inches below hull & it still cavitates.

I am going to add a spoon in front of the intake.

I am in the middle of making a 'prototype' out of stacked plywood. I am going to screw & glue it on for evaluation.

If it works, I will make a permanent one out of fiberglass. It will be thru-boilted & sealed with 3M5200.

I am copying the shape of a tablespoon, just magnified about 15X.

Cavitates under what circumstances? If your intake is 2"below the hull, not too far forward and cavitates in anything less than rippled water then you have different problem that I would try to address first.

 

[ColtonS]

Mine worked out pretty good.

I've personally never seen a "spooned" boat other than your's but it appears to work great. Since the spoon has to be bent/shaped they must be constructed of lighter material that is more apt to get dented/misshaped once again causing cavitation...possibly worse than it was before. In the shallow rocky rivers I run, a spoon probably wouldn't last a whole season that's why the flat bottom guys are going with the reverse tunnel design because it can be made of 1/4" material if need be.

 

[amk]

they make performance intake grates that scoop the water you should look into that before you make a spoon I've had a jet boat fabricated which is the one in my signature and I built one neither one needed a spoon...

heres an example
https://www.ebay.com/bhp/seadoo-intake-grate

 

[amk]

also they work to I had two identical skis except one had the performance grate and the other did not it made a huge impact on speed.

There is also a you tube video of a home made jet jon like ours where the guy tested it and it cavitated the whole time and in his second trial video he had put the grate on and it ran good.

 

[ColtonS]

Loader style grates work good but offer no protection against rocks/debris and although I cant prove it, I believe the extra bite causes the boat to ride lower in the water.

 

[CedarRiverScooter]

AMK - Thanks for the tip on the loader grate. I'll look for one on ebay. I am wondering how big of impact it would take to rip my spoon off & then I would have 6 holes letting water in.