prop hub v. pitch adjustment

[jgresham75]

Bought a new boat, previous owner included what appeared to be an unused 3-blade 21 pitch SS prop. Put prop on and did not rotate straight. Took it to prop shop and he said hub was off center and said he could re-hub. When I went back he told me he tried two hub and couldn't get it straight.

Here is where I need the help. He did put a new hub in but said it was not straight but what he said he could do is adjust the pitch on the blade to be center to the hub (meaning the center line where the shaft goes in). Is that a good idea?

That would mean that the blades would rotate evenly around the shaft but the outer hub of the prop would not rotate centraly. I hope I am explaining myself correctly. That would mean that the next time it was rehubbed, the blades MAY have to be adjusted again.

This shop is a prop shop so he SHOULD know what he is doing. The engine is 5.7 Volvo and top speed would be around 45-50 at 4500 rpm. Please help. Thank you ahead of time.

 

[Frank Acampora]

Re: prop hub v. pitch adjustment

Should, could, would. If the bulldog had boobs, if the gorilla had sneakers etc.

Sounds fishy to me. Why throw good money away trying to fix it? It may just be a bad casting.

 

[jgresham75]

Re: prop hub v. pitch adjustment

Thanks Frank for the input but so far the guy did not charge me for the new hub cause he felt bad. He said he would only charge $75 to straighten blades which is $50 less than what he quotes. I think spending $75 is worth it since new blade is 300-350.

 

[hwsiii]

Re: prop hub v. pitch adjustment

Jgresham, if the hub does not rotate centrally around the shaft there will be no way that it is balanced correctly. If the balance is not correct that means there will be some vibrational effect on the drive shaft and lower bearings, props are CHEAP compared to lower unit rebuilds. It definitely is NOT worth it in my opinion because of the potential damage to the lower unit.
I know of no way to balance an off center hub to a drive shaft, because that is where the most weight of the prop is, it doesn't matter if he can adjust the pitch. The blade itself will not be centrally located around the shaft and be unbalanced, i think that would be false economy on your part.

H

 

[Dhadley]

Re: prop hub v. pitch adjustment

I'll go along with the others, something doesn't sound right. If it's unused (as you mentioned) and it's from a good manufacturer I'd send it to them and let them deal with it. (The easiest way for a manufacturer to deal with it is replace it). I'm not really sure how a casting could be off center and pass quality control unless it was made in some wierd factory somewhere.....