A25 Propeller Shaft

[Reckman]

New albiner here. Have a quick question - I have an odd looking bushing attached to the propeller shaft, It can spin and move freely, see pictures. What is it? should it be attached to something? Seems like it could do some damage when under way. I appreciate your help.

[tribologist]

Looks like a zinc anode. You should replace it with a new one that fit tight. The make more stream lined ones too. Measure the shaft carefully so you get the right size.

https://www.boatzincs.com

Ulf

[Beta Don]

I believe the OEM shaft on the 25's is metric and someone has probably installed a standard zinc - Metric ones are not always easy to find

You can remove it, put half in a vise and use a rough file on it to take off a few thousandths from each half and it will probably lock down tight on the shaft and function as it should

Yes, I'm a cheap SOB and hate to toss a perfectly good zinc just because it's a bit too large

Don

[Reckman]

Thanks, I appreciate it.

[hetek]

Looks just like mine!

Also looks like a Metric shaft based on the castle nut arrangement. SAE shafts are usually double-nutted with a different cotter pin placement.

I got my zincs at boatzincs.com also. It's called a collar zinc. Here...

https://www.boatzincs.com/collar-metric.html

My shaft is 30mm. I think the other popular size is 25mm. Measure carefully!

[Dieselram94]

Just looking at your pictures. Is your rudder skeg cracked or corroded close to where it meets the keel?

[DesertAlbin736]

Also looks like a Metric shaft based on the castle nut arrangement. SAE shafts are usually double-nutted with a different cotter pin placement.

Interesting observation. I've always wondered about my prop shaft. The difference in diameter between 25 MM and 1 Inch is .4 MM, or 0.016 inch, where a 25 MM shaft is 0.984252 inch and a 1 inch shaft is 25.4 MM. Guessing it's metric since there's no mention one way or the other in the documentation and receipts dealing with the re-power job that were passed on from previous owners. No mention of a new shaft nor SAE replacement cutlass bearing. Also if anything the shaft was probably shortened due to installation of the AquaDrive CV unit. The original left hand prop was replaced with a right hand prop with a nut ahead of the prop, but unfortunately not enough space to put a zinc collar on the shaft. Having a zinc on the prop shaft hasn't been a priority since this boat spends 99.5% of the time sitting on the trailer just like in this photo. The longest it's ever been in the water since we've owned it is six weeks at a time on three separate occasions, and two weeks at a time on two other occasions. Even then most of the time was spent away from marinas where stray currents might be a problem. Otherwise locally it's only one or two nights at at time in fresh water.

DSCN3631crop.jpg

[ssrig]

Also looks like a Metric shaft based on the castle nut arrangement. SAE shafts are usually double-nutted with a different cotter pin placement.

Interesting observation. I've always wondered about my prop shaft. The difference in diameter between 25 MM and 1 Inch is .4 MM, or 0.016 inch, where a 25 MM shaft is 0.984252 inch and a 1 inch shaft is 25.4 MM. Guessing it's metric since there's no mention one way or the other in the documentation and receipts dealing with the re-power job that were passed on from previous owners. No mention of a new shaft nor SAE replacement cutlass bearing. Also if anything the shaft was probably shortened due to installation of the AquaDrive CV unit. The original left hand prop was replaced with a right hand prop with a nut ahead of the prop, but unfortunately not enough space to put a zinc collar on the shaft. Having a zinc on the prop shaft hasn't been a priority since this boat spends 99.5% of the time sitting on the trailer just like in this photo. The longest it's ever been in the water since we've owned it is six weeks at a time on three separate occasions, and two weeks at a time on two other occasions. Even then most of the time was spent away from marinas where stray currents might be a problem. Otherwise locally it's only one or two nights at at time in fresh water.

DSCN3631crop.jpg

Hmmm, is this fact? Would metric verses SAE have a different sized nut? I have still not determined the right nut size on my boat, I cleaned up and filed the threads on mine and a 3/4" x 10 still will not go on so I am assuming its a metric thread?? Previous owner said it had a castle nut on it before it sank. So, I will source some steel metric nuts, maybe 19mm, 20mm, 21mm, see if they smoothly go on then if one works find one in brass/ bronze.

[DesertAlbin736]

Hmmm, is this fact? Would metric verses SAE have a different sized nut? I have still not determined the right nut size on my boat, I cleaned up and filed the threads on mine and a 3/4" x 10 still will not go on so I am assuming its a metric thread?? Previous owner said it had a castle nut on it before it sank. So, I will source some steel metric nuts, maybe 19mm, 20mm, 21mm, see if they smoothly go on then if one works find one in brass/ bronze.

Similar size SAE & metric bolts & nuts may look close, but the threads are different. You'll know if you try putting an SAE nut on a metric bolt/shaft thread & vice versa. If it's the wrong type it'll jam within a half turn or so. Just like a 1/2 inch nut or bolt head is close but no cigar compared to a 12mm. Close only counts in horseshoes & hand grenades.

[ssrig]

Hmmm, is this fact? Would metric verses SAE have a different sized nut? I have still not determined the right nut size on my boat, I cleaned up and filed the threads on mine and a 3/4" x 10 still will not go on so I am assuming its a metric thread?? Previous owner said it had a castle nut on it before it sank. So, I will source some steel metric nuts, maybe 19mm, 20mm, 21mm, see if they smoothly go on then if one works find one in brass/ bronze.

Similar size SAE & metric bolts & nuts may look close, but the threads are different. You'll know if you try putting an SAE nut on a metric bolt/shaft thread & vice versa. If it's the wrong type it'll jam within a half turn or so. Just like a 1/2 inch nut or bolt head is close but no cigar compared to a 12mm. Close only counts in horseshoes & hand grenades.

yup, thats what its doing, forcing it will start galling the threads so sure seems like the wrong size, so the question is.....what is the metric version of 3/4" x 10 ?? Which size is it and can I get one? The saga continues.

[dkirsop]

Pacific Fasteners, 1st Avenue, Burnaby can likely source a metric nut for you. The other thing to check is whether you have an ACME thread as opposed to an SAE thread. The ACME thread has a square shoulder at the top rather than a sharp edge and is used in high torque situations.

[tribologist]

Both M18 and M20 is 2.5mm pitch. Very close to 10tpi but you likely have a M20 since a 3/4-10 nut would probably on go but be sloppy just like a M20-1.5 oil filter spin on just fine on a 3/4-16 thread engine... for about 3000 miles.... friend lost engine that way. Jiffy quick lube

Ulf

[ssrig]

Thanks guys, I'll give Pacific Fasteners a call, Fasten All in Duncan too.
Doesn't look like Acme threads either, I think.
Looking for someone on SaltSpring who has thread gauges.

[DesertAlbin736]

The other thing to check is whether you have an ACME thread as opposed to an SAE thread.

wiley.jpg