Prop rotation question

[Scott T-Bird]

I didn't realize that I was going to have to know this before taking my PYI Max Prop off for re-conditioning! I'm pretty sure it's left hand rotation. Boat is a Catalina 320 with Yanmar 3gm30F and Kanzaki KM2P transmission with gear ration 2.21 as seen on the stamp. I had the yard remove the prop and I didn't realize that they would remove the blades in the process of getting the prop off the shaft. When they gave me the prop, the blades were really in an odd configuration, which really freaked me out until I realized that they simply were a little careless in putting the assembly back together! As seen in the photo, one of the leading edges is reversed! Look which way blade 3 is pointed! The fact that it is marked on the opposite side is a clue.

The problem is, I don't really know which way the leading edges were oriented before this was taken apart. I guess I just never focused on this issue. Since 2 of the tree blades come to a stop with leading edge forward when rotated ccw (viewing from the trailing edge) I assume it is left hand. But I'd like to know if there is another way to confirm it. Yanmar specification sheet for 3GM30 says crankshaft rotation is CCW when viewed from the stern. I've heard some transmissions can drive the prop shaft in the opposite direction, but that doesn't appear to be the case.

 

[jssailem]

Can you find a stamp on the hub with the prop detail. Something with an L or R should indicate the shaft rotation that the prop was designed to be attached.

On the other hand, don’t the MaxProp’s blades just rotate. If this is the case do they rotate to a fixed place or rotate completely.

 

[dlochner]

Left hand rotation is not common, I would be surprised if your boat had LH rotation. The rotation is viewed from aft looking forward and it should be RH. Of course if you look at from forward looking aft, it would be a LH rotation. The usual way, is viewing from aft.

More concerning is the blade. According to PYI, it is not possible to put the blades in backward, they only fit one way. The blades go in the same way for either rotation, the difference is where they meet the gears. Time to take the prop apart. PYI has good instructions on their website. It is relatively straight forward process, just gets a little messy with the grease. I've had mine apart a couple of times.

When they removed the blades, it is likely they did not record the blade settings. Ask PYI what they should be so when you reinstall the prop you'll have the right settings. PYI has good instructions on they website.

For reference, here's a photo of my prop.

 

[kloudie1]

As Dave says, your prop is right hand unless someone repowered with a strange engine. The Kanzaki does reverse rotation so with a ccw engine output, shaft would be cw at the prop

 

[Stu Jackson]

Like almost every single Catalina model, there is an active owners association: Catalina 320 International Association

 

[Scott T-Bird]

When I had my hub off, I am able to rotate the blades independently. They instruct to put the hub back on with the leading edges feathered, and I was able to do that so that all blades are oriented in the same direction. (I did this after I realized that the hub comes off to remove the prop from the shaft). I think the guys simply didn't orient the blades properly when they reconnected the hub to give the prop back to me - blade 3 was backwards and blade 2 was also just slightly off.

Yanmar specs call out CCW rotation of the crankshaft (viewing from stern) for my engine. I think I'm mixed up ... that's right hand, right?

 

[Scott T-Bird]

As Dave says, your prop is right hand unless someone repowered with a strange engine. The Kanzaki does reverse rotation so with a ccw engine output, shaft would be cw at the prop

So if the prop shaft rotation is CW when looking from the stern, so I should have a left-hand prop?

 

[dlochner]

CW is a right rotation. Always start at 1200. Yes, this another of those boating things that is confusing as hell until you understand it and then you wonder why it was so hard to learn.

 

[Scott T-Bird]

Yeah, I think I'm mixing up the "hand" issue. I'm looking at my right hand and making a twisting turn to the left as the natural motion, when it's actually the opposite. I'll just stick with CW and CCW. So does your transmission reverse the rotation as @kloudie1 indicates? it seems that is what is not consistent. I'm disassembling the whole thing and degreasing before shipping off to PYI for re-condition. I just have to tell them the correct rotation. They will put it back together correctly, I assume.

 

[dlochner]

Scott, you're in a rabbit hole. What we all call a transmission is really a reverse gear as it changes the rotation so the prop rotates in a CW direction. When viewed from the front, the engine rotates in a CW direction, however when viewed from the rear, the shaft turns in a CCW direction. The reverse gear (transmission) changes that direction so the prop rotates in CW direction when viewed from the rear.

Do this, take a pen or pencil and hold it between thumb and forefinger. With the pen point away from you rotate the pen in CW direction. Turn the pen around so you are looking at the other end while rotating the pen CW. The end pointing at you while now be rotating in CCW direction. Do it a few times to convince your self.

 

[Ken13559]

I've 2GM20F with KM2P. Looking from stern to forward direction, the prop rotates ClockWise CW when going forward. When I ordered my Kiwiprop or Flex-O-Fold, I indicated RH prop to the manufacturers.
Hope this don't confuse an already confusing situation

 

[RoyS]

Perhaps you recall your prop walk? Right Hand Props produce a stern movement to port in reverse.

 

[kloudie1]

Like aircraft, the convention of orientation (whew big words) is viewing from the stern .. I think automobiles are the same too (except maybe British cars?)
Continued dead horse beating:
The gearbox thing .... the output from the engine turns the trans input shaft CCW and because its gear meshes with one gear on the output (prop) shaft, that gear must turn opposite the other gear. (two wheels touching at the outer circumference.. turn one ccw and the other will turn cw).. to achieve reverse, one of the main gears is disconnected and an idler gear is imposed between the shafts .. so now input is ccw, idler is cw and the output is ccw which now backs the boat up..

 

[Scott T-Bird]

Perhaps you recall your prop walk? Right Hand Props produce a stern movement to port in reverse.

I would agree but with feathering prop I don't have any prop walk.

 

[fstbttms]

I didn't realize that I was going to have to know this before taking my PYI Max Prop off for re-conditioning!

View attachment 222042

That's an Autostream, not a Max Prop.

 

[Stu Jackson]

That's an Autostream, not a Max Prop.

Interesting for you, Scotty.

If you compare the photos in post #1 and #2, the hubs appears quite different. fstbttms knows his underwater stuff, too.

So Scotty, whatcha really got dere, huh?

 

[fstbttms]

So Scotty, whatcha really got dere, huh?

It's not up for debate. The OP's pic is of an Autostream prop

 

[Stu Jackson]

It's not up for debate. The OP's pic is of an Autostream prop

Not questioning you at all. Asking Scotty to chime in here, that's all.

 

[Tally Ho]

Sure didn’t think it looked like any Max Prop as I have seen, but maybe it was really old or something…

Autostream makes way more sense.

Greg

 

[Scott T-Bird]

That's an Autostream, not a Max Prop.

Yep! I don't know what I was thinking! I even had the Autostream installation manual in my files. Well, I won't be sending it to Max Prop to be reconditioned, but since I have it at home now, I will do some servicing by myself. But I think I'll call Martec for some guidance. I'm pretty sure the previous owner bought this prop from Martec as I seem to recall I've got some papers from Martec concerning the prop.

I had already sent the servicing form to Max Prop and got an e-mail reply today. I e-mailed back that I made a mistake because I have an Autostream and he laughed and told me I could have a new Max Prop sent to me before Christmas!

While I was thinking that I had a Max Prop, I was always confused by the grease fitting, which was described in a different manner. As you can see, the zerk is right behind the zinc!