Prop to Rudder Clearance

[kvand347]

I put my new 4-blade prop on yesterday and I only had about 1/4" from the prop blade to rudder. My 3 blade is about 1/2". I did not feel comfortable enough with that spacing to keep the 4 blade on so I took it off and used the 3 blade. I could not get the 4 blade any further up the shaft.

Your thoughts?

[kvand347]

Anyone? I'd like to figure this out before I go boating this afternoon...

[docdrs]

There should be no play in your drive line fore/aft and there will only be flattening deflection away from the rudder while if forward so you should be fine. If you spin it hard in reverse there could but doubtful be a concern. As long as your motor mounts and tranny driveline are solid. just my .02which may not be worth much

[docdrs]

Oh you could take the prop to a machine shop and have them enlarge the front of the prop hole slightly so it will slide up further. Prob only have to do a 1/32 - 1/16 on the first inch of the prop shaft hole to get it to slide up further.

[kvand347]

Thank you very much Doug! I was really hoping you would chime in. I agree with you that as long as there is no fore/aft play then it should be fine...it just made me nervous it was so close! You are also right that when hammering down in forward that the prop will deflect away from the rudder. I don't know if you could spin it fast enough in reverse for it to deflect and affect the rudder.

I will try lapping the prop to the shaft with some valve grinding compound. That might bring it further up on the shaft too. If not, at least I know that it will be seated properly!

Thanks again!!

[kvand347]

Took it out this afternoon and no issues with it hitting the rudder. I'm still pretty nervous about it and may pull it off and have it machined. It is way too close for comfort. I'll go take a picture so you guys can see what I mean.

[kvand347]

Note: The chip in the rudder was there before I installed the new prop.

http://i1151.photobucket.com/albums/o621/kvand347/IMG_5922.jpg

http://i1151.photobucket.com/albums/o621/kvand347/IMG_5921.jpg

[Jetlink]

Looks like a well placed chip, almost strategic if you ask me...:D

[docdrs]

Even easier would be to grind the rudder back in this area, I doubt it would impact steering or performance

[lively]

Even easier would be to grind the rudder back in this area, I doubt it would impact steering or performanceuse a sawzaw!!! lol

[Hagman]

Sorry to bring this up. But I have never seen a propeller that close to the rudder. There usually is at least 2 to 3 inches between the two . I measured the distance between the shaft support and the propeller on my comp, there is 1 inch distance between the two. More than 3” to the rudder. Could someone along the way have replaced your shaft with the wrong length.

[wiatowski]

Sorry to bring this up. But I have never seen a propeller that close to the rudder. There usually is at least 2 to 3 inches between the two . I measured the distance between the shaft support and the propeller on my comp, there is 1 inch distance between the two. More than 3” to the rudder. Could someone along the way have replaced your shaft with the wrong length.

I would agree... you might be able to compensate with a smaller diameter prop.1" less would be a big difference.

[kvand347]

Sorry to bring this up. But I have never seen a propeller that close to the rudder. There usually is at least 2 to 3 inches between the two . I measured the distance between the shaft support and the propeller on my comp, there is 1 inch distance between the two. More than 3” to the rudder. Could someone along the way have replaced your shaft with the wrong length.

I cannot rule that out since I have just recently taken ownership of the boat. The 3 blade that was on the boat was about 3/4" away from the rudder. I think if I have the new prop machined I could slide the prop up further and not have to worry about it.

[kvand347]

I would agree... you might be able to compensate with a smaller diameter prop.1" less would be a big difference.

But that would mean buying a new prop or cutting the current one down. Not sure if I want to go that route. The performance of the new prop is very noticeable. I got better hole shot, faster mph at 3600 rpm's, and faster top speed (46 mph).

[wiatowski]

But that would mean buying a new prop or cutting the current one down. Not sure if I want to go that route. The performance of the new prop is very noticeable. I got better hole shot, faster mph at 3600 rpm's, and faster top speed (46 mph).
some prop shops will let you do an exchange. what's the current specs on the prop?

[kvand347]

some prop shops will let you do an exchange. what's the current specs on the prop?

Acme 422 Propeller 4 Blade 12.5 X 15.5 RH 1 "Bore .105 cup

Doubtful on an exchange...bought the prop used.

[CornRickey]

Does the bore mic out to 1" ? How does its measurements compare to the old one at the hub? Does the new one engage the key all the way?