strut, cutless,shaft

Indeed.... equal HP transmitted at a lower RPM due to the lower ratio gear drive = more torque therefore more stress and the need for a larger shaft.

With the material strength and required factor of safety determining the constant

D = sqrt(Hp/RPM) * Constant
if we take 240 hp at 4500 rpm as requiring a 1 inch shaft
Constant = 4.33 (this is reasonable as 4.0 is used as a rule of thumb for the constant when designing a plain carbon steel shaft for an electric motor)

For a 1.24:1 ratio transmission you would then need a 1.101 inch shaft to keep the same factor of safety with the same engine and for a 1.5:1 shaft it would be 1.211 inchs

For a significant increase in hp you need to increase the tensile strength of the shaft or risk bending the shaft.. increase in hp and lower the gear ratio and you really need to consider achieving that hp at a higher RPM or increasing the shaft diameter.

Steady Eddie bent a few shafts when he put a python with the pcm transmission in his two barefoots before he had a few shafts made with the highest tensile strength material he would find. So the factor of safety is not excessive on later model boats with higher hp and gear reduction transmissions.. although most of them at least make peak hp at higher rpms.

I don't know why the v-drives got the larger diameter shaft, but I emailed the folks at NautiqueParts about the length of the 1 1/8" bushing and they said theirs was 4 1/2" long.

I was just checking to see if anyone knew where to find a 1 1/8" bushing at 6" length, thanks.

P.S. with the v-drive in the way I'm dreading checking the alignment but I know I shouldn't put it off too long. I just want to do the cutless at the same time because mine is worn.

2nd P.S. You taught me something - I didn't know that the python direct drives got a 1 1/8" prop shaft, thanks.

HW, youre confusing shaft size on direct drives, where only the Pythons got the 1-1/8" shaft. Pretty sure all CC v-drives within the last 20 years have gotten the 1-1/8" shaft regardless of engine choice.

Hollywood wrote: You have a Python?

I guess you're asking me because of the 1 1/8" id?

Alas, no mine has the GT 40 with v-drive, no Python.

I missed "General Discussion" tab and hit "Common Questions" and saw this thread without realizing that it was getting a little old.

I'm curious, is the factory cutless 6" long or are there two pieces in the strut? All of the 1 1/8 id x 1 1/2 od cutless bushings I can find are 4 1/2 inches long. Where does the factory get 6" long cutless bushings?

I guess you just have to install a 4 1/2" cutless flush with the rear of the strut?

If you find that the set screw threads are messed (and you have a good cutlass bearing in there) up you can just use some loctite 290 on it.

Could be a 4" strut bushing installed from the front on a 6" strut, no? That might make the rear set screw unusable.

I am no expert and new to the site, but if you read through some of the threads you can learn a lot very quick. Look on www.skidim.com under struts/bearings you will see what they call a strut bearing but is actually the cutlass bearing. It is a bronze sleeved 2 piece bearing with rubber on the inside, more than likely what your seeing is not the shaft it is the outside of the cutlass bearing. However if for some crazy reason there isn't one there you will have a lot of play in the shaft and a huge problem beyond that.