Prop Shaft

[gn7]

That's interesting, and you made me go take a better look at my parts. I hadn't noticed it before (never actually looked) but the motor to V-drive shaft (1 3/8") is hollowed out. Its got a 7/8" hole down the center. I guess they really wanted to get every last 10th of a hp they could out of this thing.

The rifle drilling can actually improve the torsional strength of the shaft by increasing the surface area exposed to the rotational stresses. High end crankshafts are drilled front to rear thru the main journals. Most dirt track/sprint car torsion bars are tubular.
The loss of a few ounce of rotational mass is the bonus. Keep in mind, the material in from the center of the shaft, and has much less effect on the "rotational mass" thing.

[Propless]

Do you have a pic of that?

Its the best I can do with my phone.

[gn7]

Do you have a pic of that?

Yeah I've seen them. I believe the use of 7/8 shafts may have started that way and evolved to include the prop itself, of for no other reason than prop availability. I imagine the grinding of the shaft was a pricey affair as well, but did make the prop hunt a little easier, and a little easier to dump unwanted/unused props.

[ogshotgun]

Chris Alston's web site used to have a nice little write up on the strength increase of gun drilled shafts. I don't know if it's still there I haven't been on his site in years but it is a very strait forward easy to understand read.

i agree that the gun drilled is stronger i don't know why but in my car i had summer brothers solid axles with 33 splines i broke one , than broke another , went back to the vendor really upset they traded me for a gun drilled axle i haven't broke that one yet and its been years...

[ogshotgun]

Yeah I've seen them. I believe the use of 7/8 shafts may have started that way and evolved to include the prop itself, of for no other reason than prop availability. I imagine the grinding of the shaft was a pricey affair as well, but did make the prop hunt a little easier, and a little easier to dump unwanted/unused props.

i called my go to guy and showed him the picture you posted he said they tried that years ago to reduce rotating weight and easier to find props .. i asked how did it work out , he laughed and said i crashed the boat couldn't tell you.. lol

[Propless]

Ok, and for the big question.

Should I even consider staying with that shaft in a lake use boat ? Assuming it checks out good. Or just go through the work to step up to a 1" shaft now before the strut goes back in. Changing to a 1" would require a new (or modifying) the coupler, and possibly a new strut (I haven't measured the strut barrel yet to see if a 1" bushing will fit). I could see that shaft being very expensive to duplicate if anything ever happens to it in the future.

I don't plan on running the blower anymore so hp should be around 600, and the boat is fairly light (small stringer) Daytona flat.

[Propless]

i called my go to guy and showed him the picture you posted he said they tried that years ago to reduce rotating weight and easier to find props .. i asked how did it work out , he laughed and said i crashed the boat couldn't tell you.. lol

This probably the stuff from that boat. Story is these parts came from the SS 44 boat that flipped at Long Beach in 07.

[HotWater]

I'd say the 7/8" shaft is to reduce drag and lift. Bottom work and underwater gear in ss is a big tuning area. Some use a physically smaller strut also. Proplove, think about the affect on the boat that little stick stuck to the cav plate fin made. Shit can that shaft.

[Propless]

I'd say the 7/8" shaft is to reduce drag and lift. Bottom work and underwater gear in ss is a big tuning area. Some use a physically smaller strut also. Propless, think about the affect on the boat that little stick stuck to the cav plate fin made. Shit can that shaft.

Quiet, you just want me to part it out (not going to happen) so you can have the 8 deg.

[HotWater]

Quiet, you just want me to part it out (not going to happen) so you can have the 8 deg.

I've got a new plan, I might need a parallel shaft casale.