jet jon intake size question

duckman11
Posts: 25
Joined: 09 Oct 2017, 20:11
4

jet jon intake size question

Post by duckman11 »

I'm really unsure how to word this question properly....but here it goes.

What happens when you make the pump intake bigger than what it is
"stock"? I'm referring to the opening in the hull where the intake grate is located.
For math purposes lets say that the stock opening is 40SqIn.....what would be the down side to making that area 60SqIn?

The reason I'm asking is because I have an idea to make a pump out of aluminum to go along with the Kawasaki 900zxi engine I'm going to be using in my jet jon project. I run up the creeks here in Texas that feed into our lakes and I'm going to be crossing choppy open expanses of water so im thinking that splicing a jetski hull into a jon boat isn't going to be the strongest method of construction.

CedarRiverScooter
Posts: 1522
Joined: 13 Nov 2014, 08:01
7

jet jon intake size question

Post by CedarRiverScooter »

I don't know if a larger 'mouth' for the intake will be OK, but my experience is that deviating from an engineered design can have unpredictable results. If it doesn't perform well, you will have poured lots of work into it & then have to tear it back apart, which will be three times the work (been there, done it).

Check out PSG1 thread. He used a Yamaha aluminum tunnel, which can be welded in.

For the record, I removed my PWC-based tunnel & it had to be sawed out. The 5200-to-aluminum bond was very strong, has to be chiseled apart. The big risk with the plastic tunnel is hitting a rock.

duckman11
Posts: 25
Joined: 09 Oct 2017, 20:11
4

jet jon intake size question

Post by duckman11 »

I was kinda thinking the same thing CedarRiverScooter.

I do not a have a degree in hydrodynamics but my general thinking in most things is...'if it aint broke don't fix it". I figured that it would somehow decrease velocity to the impeller and or increase cavitation.

I've looked into using the Yamaha pump but at $1,400 that would triple the cost that I have in this project so far.

The worst environment that this boat will see would be a sand bar or small log jam. There are not many rocks in the creeks around here in north Texas.

CedarRiverScooter
Posts: 1522
Joined: 13 Nov 2014, 08:01
7

jet jon intake size question

Post by CedarRiverScooter »

I'm seeing alum intake tunnels on ebay for $60.

You would still have to make a pump mount from scratch.

The big advantage to using the plastic PWC insert is that the pump & engine mounts are all aligned, makes the build go well.

I recommend mounting the intake pickup several inches below the hull, to eliminate cavitation.

duckman11
Posts: 25
Joined: 09 Oct 2017, 20:11
4

jet jon intake size question

Post by duckman11 »

scooter...

What are you putting in the ebay search to find these tunnels?

CedarRiverScooter
Posts: 1522
Joined: 13 Nov 2014, 08:01
7

jet jon intake size question

Post by CedarRiverScooter »