Another bent prop question on performance

[Swivelhart]

Hello, i have never posted a prop question before. Last night I was filing off the nicks on my prop and just trying to smooth things out. As I rotated the prop to the next blade I, for the first time, noticed that one of the three blades looked significantly different than the others. U I pulled the prop off and put it on my table and measured it. What I found is that the one blade is (and I dont know if there is proper terminology) bent in a full half inch more than the other. The boat seemed to speed along fine that last trip out in the fall and there are no significant nicks indicating a hard blow. My question is two fold. Can it be fixed? I assume the answer is yes. The second is how would this affect performance? Not that I plan on leaving it bent! Would this significantly reduce top speed, take off?

It is off of a 1976 70hp Johnson on a 16ft Glastron

 

[Johny25]

Re: Another bent prop question on performance

Well it looks like that blade has been ground down a lot. It looks like they are bent the same but that blade has a much smaller ear. The more you grind and file the farther down that speed square it is going to measure. I don't think they can add on to an aluminum prop : (

Someone probably had a large ding in that blade from hitting something and ground the heck out of it to get it out......?

 

[Swivelhart]

Re: Another bent prop question on performance

What do they usually charge to fix a prop anyway?

 

[Johny25]

Re: Another bent prop question on performance

Guess it would depend on how bad it is and what had to be done to it. But like I said, I don't think they can make that blade back to its original size since it is aluminum. Props are made by a casting process in one piece and I do not think that aluminum is weldable grade aluminum. On a steel prop they can weld to it and add on.

I don't believe your prop is bent, I just think it has been ground or filed down to far on one blade giving it the appearance of a bent blade.

 

[steelespike]

Re: Another bent prop question on performance

They can weld it I've had them repair props with with quarter sized chunks out of it.
The question is ,Is it cost effective?Also its possible ythe prop is worn or filed undersize.
If the prop is the same age as the motor it may be time to replace and keep they old one as a spare.

 

[Swivelhart]

Re: Another bent prop question on performance

I will do some more measurments tonight. looking at that blade compared to the others makes me think that it has not been filed down that far. My reason is this: If I imagine more material on the end of it it would still be further in than the other two ears because of the angle it is at. I hope that makes sense. Another words the angle is off which is why I think it is bent. Also my lower skeg is slightly bent to port...maybe 1/4 inch. I dont know if it happened at the same time or not but just throwing out my observations

 

[cribber]

Re: Another bent prop question on performance

Just comparing picture to picture the distance from the hub to the outermost tip of each blade the second picture appears to be shorter in overall length. Look up the cost of a stock aluminum prop here and then get an estimate to have yours fixed. You might find it's cheaper to replace it than fix it. If so you can take the old one and keep it on hand as an emergency spare to pull you out of a jam if you hit something and spin the hub.

 

[Johny25]

Re: Another bent prop question on performance

It is the third pic, and the whole blade including the top edge in the pic looks filed down. It doesn't angle up as high because it looks as it has been filed along that top edge or trailing edge of the blade also. Each pic is a little different distance and angle but it is easy to see the third pic has a smaller blade overall.

 

[Swivelhart]

Re: Another bent prop question on performance

I appreciate the thoughts and observations...i forgot to do measurments last night. I will post my conclusions later.
I agree that in the picture it does look shorter...
As many others on here money is an issue. The aluminum propellers are pretty cheap though.

 

[wadeonminnetonka]

Re: Another bent prop question on performance

I guess if it were my money, I would run right out and get a new prop today. If the prop has been ground down as much as it looks like it has, then the prop is out of balance, which puts a lot of strain on the internals of the lower unit and the motor. Lots cheaper to buy a new prop than it is to replace hard parts in the bottom end when you would not have had to otherwise. Save on gas too. If it costs me $200 to fill the boat, and new prop is $250, I don't have to save a lot of gas on every tank to make the new prop cheaper than the old one.

 

[fishrdan]

Re: Another bent prop question on performance

I agree with SS, buy a new prop and save that for a spare. Prop (aluminum) repair around here was $60 last time I checked,, for $100 you can buy a new prop AND keep yours as a spare.

 

[Blacksting]

Re: Another bent prop question on performance

some good stuff here about alum. props. i happened to be in the shed last night and thought about welding my prop . it has a dime size chip in it and if iu can mig weld some alum. to it and grind it down , i'd have a good spare . anyone know a good proceedure to get it within 90% shape ?

 

[Swivelhart]

Re: Another bent prop question on performance

Finally got around to checking the prop closely. All the ears are the same size. I traced one with a piece of paper very precisely and then checked all of them one at a time against the template. All are the same...
If I can afford it I will buy a new prop because I agree that it would be nice to have a spare. If not, it will get bent beck to shape.

The last one is a better picture to compare them together visually. My previous post with the measurments were at odd angles which definately gave the impression of them being