2022 FIREFISH 17 CONVICT 2.0

[neilsleder]

View attachment 257104

From what I’ve seen that chart is wrong lol. My neighbour has a LSA in a custom weld and a 212 with a 4.0 impeller. It’s 13.5 gph average easy. Chris his boat with a 2.9 in his pump with crazy good closer to 8gph. But in that chart the lsa has a 3.4 so they would have to baby that motor to not get it to spin right out. The lsa with spin a 4.0 out pretty easy even with a 105mm insert

 

[NoBrakes!]

LSA is a thirsty bastard

 

[Chrisco]

What rpm should the 6.2 be running at for top rpm?

For me I like nothing less than 4400 the 6.2 di does not like to be lugged it likes RPM

 

[06 Dragon]

Sorry to derail your thread Chrisco. Another great build. I am sure you are itchin for that first water test.
We need the moderators maybe to move this impeller / jet boat talk to it own thread. My 6.2 is spinning a 4.0 kw 4200 to 4400 rpm. No problems.

 

[Chrisco]

Sorry to derail your thread Chrisco. Another great build. I am sure you are itchin for that first water test.
We need the moderators maybe to move this impeller / jet boat talk to it own thread. My 6.2 is spinning a 4.0 kw 4200 to 4400 rpm. No problems.

impossible I would bet it is not a 4.0. Unless your 6.2 is built to 550 hp. Do the math, there is no stock 6.2 or 6.2DI that can spin a 4.0kw to 4200 or 4400 the power is just not there.

 

[neilsleder]

Sorry to derail your thread Chrisco. Another great build. I am sure you are itchin for that first water test.
We need the moderators maybe to move this impeller / jet boat talk to it own thread. My 6.2 is spinning a 4.0 kw 4200 to 4400 rpm. No problems.

Let me rebuild and it won’t spin it that fast anymore

 

[Chrisco]

Some food for thought Randy. To turn the impeller a given rpm, an engine must make at least as much HP at that rpm as the impeller absorbs at the same rpm.
For the 212 with the 3.4 kw impeller, the ZZ383 engine will max out at about 4000 RPM (depending on elevation) as HP absorbed begins to exceed the HP produced.
With the 4.0 kw impeller, the same engine would max out at 3700 RPM. Even though the ZZ383 can make 425 hp, it cannot get past 272 HP.
Generally fuel efficiency begins to suffer above 80% of max RPM, which for the 4.0 kw above setup is 2960 RPM.
Also impeller selection should be such that WOT falls somewhere between the peak torque RPM and the peak hp RPM.
For the 383 with the 4.0 kw impeller a WOT RPM of 3700 is such that it's LESS than the peak torque RPM of 4300. The engine CANNOT run in its most efficient range and will lug. Computerized engines can adjust for this, but old school carbureted engines may be at risk of damage. Maybe.

The LS3 6.2 litre
max 4000 RPM with the 3.4 kw
max 3500 RPM with the 4.0kw
Probably want to run the 3.4 with this set up

The LSA 6.2 litre SC
max 4500 RPM with the 3.4 kw
max 4100 RPM with the 4.0kw
Easily handles the 4.0 kw. However runs a roots style super charger, and prefers premium fuel . Big $$

 

[Chrisco]

Any brand new 6.2Di with a 212 running a 4.0kw max rpm is 3650 to 3700 WOT fact.

 

[snoflake]

Sorry to derail your thread Chrisco. Another great build. I am sure you are itchin for that first water test.
We need the moderators maybe to move this impeller / jet boat talk to it own thread. My 6.2 is spinning a 4.0 kw 4200 to 4400 rpm. No problems.

I was going to say maybe your tach is out, but didn't want to start sounding cheeky.

 

[Chrisco]

I was going to say maybe your tach is out, but didn't want to start sounding cheeky.

Way out.

 

[06 Dragon]

New tach installed with the engine.

 

[06 Dragon]

It was spinning out the 3.4

 

[Chrisco]

It was spinning out the 3.4

That doesn't rally mean anything, what engine and pump are you running ? DI , LS3, modded or stock ?

 

[NoBrakes!]

another factor is the intake... if the grate and intake are shitty... it wont load the pump and it'll spin out under less rpm...

 

[Chrisco]

another factor is the intake... if the grate and intake are shitty... it wont load the pump and it'll spin out under less rpm...

There is defiantly something strange like this happening.

 

[Chrisco]

Some new pics.

 

[NoBrakes!]

I love the polished bump rail

 

[06 Dragon]

Another great looking boat Chrisco!
Is that color plum crazy purple?

 

[Chrisco]

I love the polished bump rail

He paints the rail on every other boat I make him do mine this way on all my boats.

 

[Chrisco]

Another great looking boat Chrisco!
Is that color plum crazy purple?

Its very close.