Flexible Shaft Coupling

[dkall]

Just sent them to you. In two formats like I send Allen so hopefully one of them will open for you.

[never monday]

WOW!!!
I'm going with a prop that isn't deploying correctly. I had this happen to me on a Maxprop 3 blade. I missed one blade by a tooth and it shook the boat apart.
I'm not familiar enough with Autoprop to label a specific part or set up scenerio. I looked at their site and it wasn't helpful. I have heard of another feathering style prop that had plastic stops for the blades. one of these had gone bad and allowed the blade to over pitch and vibrate. Can you get the prop off easily enough?

[dkall]

I most likely can but the blades auto deploy. Basically they're to self adjust all the way thru 360 degrees. What ever is best. The each freely swing around their own axis. But being in the deadwood of the boat; see my pic above, and spinning fast enough to drive me at hull speed at only about 1350 rpms I' suspect there is more than just a blade off. I will when I get a chance and get back to the boat look at all the engine mounts and if I can check the blades out and see that they all freely rotate.

Thanks for your time.

[never monday]

So your making hull speed at half power. I'm cautious to blame the deadwood as the other 42 you mentioned works. Will it get to 2800? even with vibration?

[Alan Wheeler]

Pat here is some relevant info to get you upto speed.

My engine is a Perkins 4-236 with a 1 1/4" shaft and a 21" Autoprop. The Autoprop is giving me some serious vibration. I've contacted Autoprop and am waiting yet for a resolution. They recommended the 21" prop and a 20" prop was what was on there. My tranny is 1.91:1. Engine mounts are flexible, fixed coupling and a bronze stuffing shaft log with a stuffing box on a hose.

Considering that none of these issues were an issue w/ the fixed prop. Same bearing, same shaft, same engine same shaft log. New prop. I have considered that it might be something else but I know of another WS that has an Autoprop same exact setup as mine and his is a 20" model. Don't know if I reported that memory of ABYC recommendations have a prop dia 16 to 1 and the prop on my boat that Autoprop recommended was a 21"

On mine now at 1400 rpm I get more than a vibration, more than a hum the shaft begins to bow and I feel the shutter thru the entire boat. At 1400 I'm moving at 7.5 knots or there abouts as reported on a GPS traveling two ways. I don't have any vibrations below 1400. At the dock the vibration occurs approx at about 1600 in forward and 1800 in reverse. All other speeds are ok up to those rpms.

[Alan Wheeler]

Arrrrr, OK I think I am understanding this prop a little more. I looked at the video on their site.
What it looks like is that the pitch is actually set by the blade design, not the angle it sets to. It is not a "self pitching" design as such but more accurately a self feathering design. So it is important to get the right blade model for your boat/engine and the correct blades and most importantly all three blades MUST be identical in pitch.
With the blades set so far back over the hub, I now understand how the prop could have enough fulcrum to bend the shaft like that. The driving force is developed a long way back at the end of the shaft and not up close to the bearing where most fixed blades are sitting.
From what I have seen in the specks, I think you should have an H5 to H6 and a pitch ratio of around 430. How does that match up to what you have??
I strongly suspect one blade is incorrect.

[never monday]

Heres a thought. If this was a new prop. Is it posible it has a mismatched blade?