What size propeller shaft for a crackerbox?

[Harald1966]

Hi.
What diameter size do you recommend for a 15' crackerbox with mercruiser 350?
Is one inch (25mm) OK?

[Roberta]

1" shaft with 1/1 gear ratio transmission. Any gear reduction might require a bigger shaft and more pitch and diameter prop. Big motor for a Cracker Box.

Roberta

[Harald1966]

I have a Borg Warner Velvet drive ratio 2,1:1
Direct drive not possible...

[Roberta]

A 1-1/8" shaft would be better because you will have to use a bigger, more pitchy prop to handle that power and ratio.

Roberta

[kens]

A 1-1/8" shaft would be better because you will have to use a bigger, more pitchy prop to handle that power and ratio.

Roberta

NO !!
You do not put a V-8 in something as light as a crackerbox and then put a reduction gear on it.
Much less a 2.1 : 1 VelvetDrive.

[kens]

I have a Borg Warner Velvet drive ratio 2,1:1
Direct drive not possible...

For something as light as a Crackerbox, a 1:1 gear MUST be possible.

for something like a 350 V8 + 2.1:1 gear a shaft of 1 3/8" with a prop 20"dia. is possible,,,,but NOT in a crackerbox

[Roberta]

I totally agree with Ken on this. A really small aluminum V8 or V6 is appropriate for a Crackerbox.

Roberta

[kens]

I totally agree with Ken on this. A really small aluminum V8 or V6 is appropriate for a Crackerbox.

Roberta

No, the Crackerbox was designed around the ubiquitous SBC, the 350.
it will accept all the cam, heads, carbs, hot rod parts, et. al.,,,,
BUT, It was NOT designed around a reduction gear.

[TAB]

All of the cracker box guys i know, ( granted they race them) run a direct drive. They want to use the prop as a brake into slow down. They don't even use a free wheel or throw out barring. I would recommend for a pleasure boat you do.

[Bill Edmundson]

Harrold

What HP and max RPM are you planning to run. Also, would like the total weight of the boat, including you and fuel.

Bill