Question about Crackerbox

[jack zeeman]

Hello felow boaters I build a Crackerbox but when I give gas he Flips over.
What is a Wright prop for this boats?

 

[RobertDoak]

Hello Jack...
Beautiful Crackerbox...
Interesting what you said....I built mine over the summer and keep in mind that the crackerbox is a little squirrly to begin with...mine is a Zippkits and the 26cc acts like its too powerful...and I can never use full throttle...but to be honest I haven't been able to fully adjust it either.
I have a Bob Austin 3 blade prop...7016/3
#101724...and the Right prop...well thats a multifaceted question..in my short experience with boats..we can have the same boats ..but driving styles, how the boat was built and setup will dictate what prop works best...
But off the bat it sounds like its too loose..by either the strut is not right or the balance is off...about 34% is where it should be...nice idea about the engine cover...
I hope this help...there are several here that has Crackerbox boats and perhaps someone else can add there experience....

 

[BobLondress]

I do not see a turn fin, it’s possible the lack of it is causing the flip from torque

 

[BobLondress]

I have never had mine flip from acceleration, now going into a turn wide open is a different story.

 

[john v]

when we ran mod motors in crackerbox my buddy ran a 4 blade prop, not sure with stock motors what is the right one, bob Austin would know

 

[Dennis Somers]

Jack, don't get ahead of yourself trying to get "the right prop" for this boat.
There are a number of things that need to be changed/adjusted to settle it down first. The drive strut needs to be parallel or angled very slightly down ( negative ) from the hull bottom. The trim tabs can be adjusted the same ( trial and error ) for stability ( small adjustments ). I can't see from the pics, but I assume you have a tuned pipe on that header. If you do, that "wrap forward and back" style header, is too long to "tune" the exhaust properly. It should be changed out to a proper 90 degree header, and the pipe needs to be adjusted to the proper length on the header for proper engine power. The exh. on a 2 stroke engine is not just a pipe to get the smoke out, it helps make much more power when properly matched to the engine. It's not a good idea to split ( Y fitting ) your water feed, because neither the engine nor the exh. will get a good feed. If you boat in cool waters most of the time, run the water first to the lowest nipple on your exh. flange, and then to the lowest engine nipple. This will cool the hottest part of the engine first, and pre-warm the water slightly for the cylinder head. If your water is always warm, feed the head first and the exh. second. ALWAYS water IN LOW, and water OUT HIGH. Also, gas motors with inside the hull exh., need A LOT of fresh air coming into the hull ( much more than that scoop can manage ). As well, they need even MORE heated air outlet to allow the motor to breath.
After the hull is settled down ( as much as a cracker can LOL ), you can consult with the pro prop guys for a descent prop to get your motor loaded properly.

You have a nice boat there, and a little work ahead to REALLY enjoy it. I hope that helps ya.

 

[MikeStewart]

Cracker box's don't usually turn at full throttle. Try letting off and blip the throttle through the turn.

 

[Grimracer]

To Qualify.. i do not race gas boats or have a cracker box (anymore).

I have however spent time designing and testing them.. one consideration would be to move the prop back under the boat. If i remember 15% from the transom forward to the trailing edge of the prop was the magic number.

Regards

Grim

 

[jack zeeman]

Thank you all for your respons and advies, I have Lotus to door the
Cracker and with your help it must come to a good resultaat.
No are we waiting here for nice Wether .
I keep in taches
Grt Javk

 

[RobertDoak]

Hello Jack..
Any update on your Crackerbox