Do it yourself prop repair

[KatyTX]

My wife has pulled a little too far in our lift a couple of times and hit an I-Beam with the prop. Both times it has been only one blade damaged where if "folds" the "ear" of the blade a little bit.

So I have taken off the prop, put it in a vice, done a little bending, and little hitting with the ball peen hammer.

So am I crazy to be doing this on my ACME 1235? I have a spare, currently out for proffesional repair at about $160 for similar minor damage as described above.

What would you do? Am I making more problems than I am fixing?

[DanielC]

RE: Do it yourself prop repair

If you can get the prop back to where it looks and feels good, and does not vibrate on the boat, you should be OK. Be careful with a new Acme prop, the machined edges can be very sharp.
If the prop still vibrates, even a little, you should send this prop in when you get the other prop back.
If you bend the metal repeatedly, it will work harden, and eventually break.

[robertsmcfarland]

No problem, have done the same thing any time I have bent my prop

[KatyTX]

Sharp? Uhm, yes. I have a "Dora" bandaid on my thumb to prove it from my little repair work a couple of hours ago.

I think I'll stick to minor repairs. Good point on making it more brittle. I was out of town during the week, my wife took the kids out during the week, and I noticed withing 30 seconds of getting in the boat there was a problem based on a lot of vibration. She also left the ballast full.

The goodnews is at least she is taking the kiddos out by herself. Even got my 6 year old to try and wakeboard.

Tim

[WakeSlayer]

Mrs. Wakeslayer was always too nervous to take the big boat out. Despite my protests she just wouldn't do it. I got her the Mustang last year and she will take that out frequently.
His and hers!

[IDSkier]

I have used a crescent wrench as a straighteneing tool for minor bends with pretty good results. Just take your time and be careful.

[coinless]

I was told by James propeller the naked eye could not tell if it were out of balance or not. After making adjustments they put it on a bench and if the prop moves it is out of balance and the have to grind or weld +/- to make it static.

[Roddyj]

for future reference, i believe 'bay propeller' will do a refurbish job for like 60 bucks. they did a great job on mine.

[DanielC]

I agree it is very difficult to "balance" a propeller by eye. Notice I said that if it looks and feels good, AND does not vibrate on the boat you should be OK.

I believe most of the causes of vibration from a propeller are caused by the blades not having exactly the same contour, or pitch, or position to each other blade.

On an inboard boat, V, or direct drive the propeller does not run true to the direction of travel. The prop is always running at an angle, because it is impossible to get the propshaft out of the bottom of the boat without the angle. This changes the angle of attack of each blade as it rotates. This angle causes the starboard side of the propeller to produce more thrust on a right hand propeller, and more thrust on the port side on a left hand propeller. This difference in thrust is what makes a Ski Nautique back to the port side, and a Mastercraft back to the starboard side.

If your propeller was not vibrating before you hit something, and vibrates after impacting an object, and a piece of a blade is not missing, the weight of each blade is probably in "balance". However one or more blades could be out of position, and not making exactly the same thrust as its angle of attack changes at it rotates around the propshaft.

Having said all that, I realize that a propeller is a much more complicated item than most boaters are aware of. Each blade has to have the exact same angle. Each blade has to have the leading and trailing edges in exactly the same plane, and this plane has to be perpendicular to the propshaft. Each blade has to have the exact same curve as the other blades. Each blade has to have the same cup. Each blade has to be exactly clocked correctly at 90 or 120 degrees. The hole has to be centered. The hole has to be exactly perpendicular to the plane the blades rotate in. The key has to not make the prop tip slightly as the prop is seated on the taper. The taper has to be clean.

It is impossible for you to check all these items, unless you have a fully equipped layout shop, and understand all the principles involved in measuring them. However, if the prop does not vibrate on the boat, you can assume the prop is reasonably straight.

[KatyTX]

I agree it is very difficult to "balance" a propeller by eye. Notice I said that if it looks and feels good, AND does not vibrate on the boat you should be OK.

I believe most of the causes of vibration from a propeller are caused by the blades not having exactly the same contour, or pitch, or position to each other blade.

On an inboard boat, V, or direct drive the propeller does not run true to the direction of travel. The prop is always running at an angle, because it is impossible to get the propshaft out of the bottom of the boat without the angle. This changes the angle of attack of each blade as it rotates. This angle causes the starboard side of the propeller to produce more thrust on a right hand propeller, and more thrust on the port side on a left hand propeller. This difference in thrust is what makes a Ski Nautique back to the port side, and a Mastercraft back to the starboard side.

If your propeller was not vibrating before you hit something, and vibrates after impacting an object, and a piece of a blade is not missing, the weight of each blade is probably in "balance". However one or more blades could be out of position, and not making exactly the same thrust as its angle of attack changes at it rotates around the propshaft.

Having said all that, I realize that a propeller is a much more complicated item than most boaters are aware of. Each blade has to have the exact same angle. Each blade has to have the leading and trailing edges in exactly the same plane, and this plane has to be perpendicular to the propshaft. Each blade has to have the exact same curve as the other blades. Each blade has to have the same cup. Each blade has to be exactly clocked correctly at 90 or 120 degrees. The hole has to be centered. The hole has to be exactly perpendicular to the plane the blades rotate in. The key has to not make the prop tip slightly as the prop is seated on the taper. The taper has to be clean.

It is impossible for you to check all these items, unless you have a fully equipped layout shop, and understand all the principles involved in measuring them. However, if the prop does not vibrate on the boat, you can assume the prop is reasonably straight.

All I can say is, "Wow!"

As an update, my quick fix appears to have worked. Vibration before was extreme and going over 30 mph was impossible. Now, I can hit 40 mph with no noticeable vibration, but having said that will still probably send out prop for professional fixing since I have a spare.

Quick questions for the panel of experts here, I have always understood that as I drive forward, the prop wants to tighten or move "up on the shaft", so I assume the prop wants to come off the shaft when I back up. Is this right? Also, does the the nut want to tighten or loosen as I back up or move forward. I only ask to see if I need to worry about how tight the nut is. Lastly, since the cotter pin is behind the prop, or out of the way frm wate is it "flows" by, does it mater how I "spread" the leg on the pin so long as it is out of the way?

[DanielC]

The taper of the prop shaft, and propeller bore should hold the propeller. The prop should not move when shifting from forward to reverse, at all.
The nut also should stay tight. There is a very slight tendency for the nut to loosen when accelerating forward, and tighten when the throttle is closed, but the propshaft nut should be tight enough to not actually loosen.
I try to get the legs of the cotter pin as close to the prop shaft as possible.

[KatyTX]

The taper of the prop shaft, and propeller bore should hold the propeller. The prop should not move when shifting from forward to reverse, at all.
The nut also should stay tight. There is a very slight tendency for the nut to loosen when accelerating forward, and tighten when the throttle is closed, but the propshaft nut should be tight enough to not actually loosen.
I try to get the legs of the cotter pin as close to the prop shaft as possible.

Thanks for the quick reply. I had heard that since the prop pushes in forward and pulls in reverse, that is why the prop could come off in reverse if you had a loose nut and not cotter pin. Regardless, I use the staineless steel nut with the plastic on it and always a new cotter pin. I never did like the brass nut with the cut-outs for the pin as it was always hard to lign up exactly and still feel that the nut was tight.

[WA-H2O-SKI]

I believe Acme suggest 30 ft/lbs. and I use a nylock stainless nut. I agree the castle nuts SUCK. When I bought me boat the nut was loose on the shaft....... (castle nut).

[TravisFling]

I think that taper's in general are just amazing. Blows my mind to think about. That and the physics behind a tapping head.. How does it know what to do!??!! Anyway, the nut should only be there for security, so you're not dropping a prop at the bottom of the lake if something gets the taper "unstuck", either physically (log) or harmonically.

[steve-o]

Castle nuts on a propshaft aren't meant to hold the prop on. They are there to prevent the prop from falling off should it become dislodged from the shaft. You use a castle nut the same on a propshaft as you do on any other castle application (wheel bearings, etc). You tighten it down until the item seats (at this point it isn't going to go anywhere) then you loosen the castle nut to allow the pin to be installed. The taper is what holds the prop on. It is a press fit, just like hubs on a wheel, etc.