Help idenitfying prop shaft collar

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VT_Jeff
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Help idenitfying prop shaft collar

Post by VT_Jeff »

My sailboat is a C&C 29, 1983. Yesterday I was swimming under it and noticed, I think for the first time, that there is a bronze, bullet-shaped collar on the prop shaft forward of the strut/bearing. This collar is free-spinning/sliding on the shaft and naturally rests on the strut due to gravity. The prop is a folding/racing prop, not sure if that is pertinent. What's the collar for and is it supposed to be free or is it supposed to be pinned to the shaft?

Also, the shaft didn't feel loose in the cutless bearing but it was easy to spin by hand. My memory is that they are typically hard to spin by hand, at least on the '68 ski boat I used to have. Is that a sign of a cutless bearing on it's way out or is that to be expected when it's in the water/lubricated?

Thanks,

Jeff
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Re: Help idenitfying prop shaft collar

Post by Fuzz »

Give the shaft a good shake. If you can feel it move it is time to replace it. My buddies cutlass in his sailboat seems to have lasted 30 plus years. On my fishing boat they only lasted a couple of years but I was running in very nasty water a lot of the time. Are you sure the the collar is bronze? My first thought is it is a shaft zink that has come lose.

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Re: Help idenitfying prop shaft collar

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Fuzz wrote: Fri Aug 07, 2020 12:53 pm Give the shaft a good shake. If you can feel it move it is time to replace it. My buddies cutlass in his sailboat seems to have lasted 30 plus years. On my fishing boat they only lasted a couple of years but I was running in very nasty water a lot of the time. Are you sure the the collar is bronze? My first thought is it is a shaft zink that has come lose.
Zinc! I didn't even think of that. It could be, I was looking at it through goggles underwater. I'll take another look and see if there is a zinc elsewhere on the shaft, otherwise, that could be it. I will say that if it is the zinc, it's untouched by galvanic corrosion, was not rough at all, maybe why zinc didn't occur to me.

The boat will be out of the water in another few weeks/month and I can tend to whatever so it's not a big deal, just made me scratch my head a bit.
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Re: Help idenitfying prop shaft collar

Post by Fuzz »

It is good you are planning on hauling it soon. If the zinc is loose it is not doing its job and something else may be getting eat up. Look close at all the other under water gear. If any looks sort of pink it has been leaching the zinc out of it. When you pull the boat post pictures.

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Re: Help idenitfying prop shaft collar

Post by VT_Jeff »

Fuzz wrote: Fri Aug 07, 2020 12:53 pm My first thought is it is a shaft zink that has come lose.
Took another look and I'm sure this is correct. There was a set screw that we tightened. Here's what baffles me though: due to the style and the location, the only way to change it is by pulling the shaft! I had to pull the shaft on my ski boat once and it was a royal PITA, as I recall. The previous owner was a racing nut, hence the folding prop and probably this style of low drag anode. But that seems like a lot of hassle to pick up a 1/10 second around the buoys.

In any case, appears there is some movement with the shaft so I'm going to plan a swap on the cutlass this off-season, unsure if I'll tackle it myself or let the marina guy do it. The anode, as I said, appears perfect, which either means something else is being sacrificed or there's just not a lot of corrosion going on when the boat is on a mooring for 4 months a year in freshwater. I'm guessing/hoping it's the latter.

I'll check the other stuff when it's pulled. There's not a ton of other metallic gear underwater but I'll look for any pink, great tip.
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Re: Help idenitfying prop shaft collar

Post by Fuzz »

Being in fresh water will make a difference with the corrosion. I think there are different anodes for fresh water. Maybe one of the guys who boats in fresh water will chip in. I will be surprised if you do not find the anode is spilt when you get it out of the water.

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Re: Help idenitfying prop shaft collar

Post by Fuzz »

I looked online and see you have a fin keel boat. I saw a collar zinc ahead of the strut on them also so that is normal.
I have never had a strut hung shaft so it might be easier to change the cutlass for you but all of them I have done involved pulling the shaft. I will be helping a good friend change his cutlass this fall. The way his Downeaster is built we will be jacking up the engine and pulling the shaft out under the engine. :help:

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Re: Help idenitfying prop shaft collar

Post by jacquesmm »

I missed that question.
Yes, it is a zinc anode. Those MUST be replaced regularly, they are sacrificial.
You don't have to pull the shaft.

To change the strut bearing, you must pull the shaft. I wouldn't bother unless you have vibrations.
On a boat that size, the shaft should turn by hand, it's normal.
I prefer solid bearings like Thordon.
A small portable press will help to install a bearing but I use a trick.
I buy some dry ice and put the bearing in it, It shrinks just a little bit but enough to push it in the strut with a large clamp.
I have used that trick many times.
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Re: Help idenitfying prop shaft collar

Post by VT_Jeff »

jacquesmm wrote: Sat Aug 08, 2020 2:38 pm
I wouldn't bother unless you have vibrations.
On a boat that size, the shaft should turn by hand, it's normal.
Since I got the boat, about 6 years ago, there has been a "vibration" at lower rpms, but once I get it up to about 2400, my normal operating rpm, it smoothed out completely, and that is still the case. I was led to understand that the vibration at lower rpm was due to resonant hull frequency. The pre-purchase inspection report indicated that the cutlass bearing was fine at the time of purchase. I've only gone through maybe 4 or 5 20 gallon tanks of diesel since I've owned it so there hasn't been a ton of engine use.
There are only two seasons in Vermont: boating season, and boat-building season.

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Completed Jacques Mertens FS14LS + 10%, Build Thread
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Re: Help idenitfying prop shaft collar

Post by Fuzz »

The vibration could be normal for your engine. Lots of small engines do that until they are up to speed.
My buddy can find no evidence that the cutlass has ever been changed in his forty year old boat. Yours could be the same. The good news if you do need to change it out you will likely not own it long enough to need to do it again.
When you put a new shaft zinc on it make sure it is a two part one that can be changed out easily.

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