Shaft Zinc Necessity

[Jkraft]

I am sure I will get some grief for even asking this question. When I bought my 28 the C7 collar zinc was missing on the shaft. When I bought it, it had a tad of vibration in the drive train. I added a zinc to it and i swear the vibration was magnified. I am curious to see if it goes away again if I leave the zinc off. I will get hauled mid season for a bottom cleaning and hull detail. Would I be ok leaving it off until then? I am in brackish, mostly fresh water. I have a galvanic isolator. I have zincs on my rudder, trim tabs, thruster, and a large rectangular zinc on my transom. At the end of the season my zincs still look good annually. Any thoughts on this?

Thank you,

[Pitou]

My thoughts are to get to the root of the vibration. it could be a number of things starting with the propeller balance then the shaft log's cutlass bearing and shaft alignment. That's where my first focus would be. If all checks out there, it's onward to engine mounts and inspecting the shaft for true.

I say find out the route of your problem and get a shaft collar or prop nut zinc on for protection.

[Tree]

I know you’ve had a lot of work done with regards to the vibration but has the shaft been dialled in - it could have a slight bend in the middle and be whipping.

I’m going through the same scenario at the moment. I’ve got a small amount of vibration at cruising RPM that came about from the 200’ of line I got caught round the propellor. I’ve just had the propellor re worked, new cutlass bearing and I’ve also refurbished the cutlass bearing housing since the spigot that fits into the stern tube was going pink and starting to break up on its extremes.

Prop shop told me I had a small ding in the prop. The cutlass bearing was worn by 1mm on its diameter. Shaft has been clocked in at the prop end and only had .002” error.

If the vibration is still apparent, I will need to pull the shaft at some point and check it for true between two centres. I feel it maybe the case and will need straightening. I’d do it now but the yard need the space and got me out as a favour so I could deal with the prop end. I may well pull the engine later in the year for any rust treatment and check the shaft then.

[Jkraft]

Hey guys, so as far as the vibration goes here is what we did.

New motor mounts

Prop tune up

Engine alignment

Checked shaft coupling

Sent the shaft out to be checked - came back perfect

New cutlass bearing

New rudder bearing

The vibration is also confirmed to not be in the motor. That being said, I’m just brain storming at this point. I’ve got a fortune in chasing this down.

The service yard working on the boat is very reputable and believes it’s just “the boat”.

[Pitou]

Well, you sure are in a quandary considering all of the work that you've done chasing the vibration. With all of that work was there any improvement to the vibration?

[Jkraft]

Maybe a little bit but not what I was expecting.

[furball]

Since you’re brainstorming and the boatyard says it’s “ the boat”. You’ve done everything else. Ever see this on an Albin?

026C058F-3749-482B-B461-9D379DDFC998.jpeg

Just wonder if what you feel is some kind of cavitation? I’ve often looked at the back edge of my skeg and thought that square back can’t be great for clean water to the prop. I wonder if this helps?
This is the only Albin I’ve seen with this. Don’t know if others have it.
Just thinking out loud
John

[Jkraft]

Since you’re brainstorming and the boatyard says it’s “ the boat”. You’ve done everything else. Ever see this on an Albin?
026C058F-3749-482B-B461-9D379DDFC998.jpeg
Just wonder if what you feel is some kind of cavitation? I’ve often looked at the back edge of my skeg and thought that square back can’t be great for clean water to the prop. I wonder if this helps?
This is the only Albin I’ve seen with this. Don’t know if others have it.
Just thinking out loud
John

Hey John! It absolutely feels like cavitation to me. My biggest concern all along was that I’m going to wear something out premature but I I’ve been assured that I won’t. The fact that it does it still bothers me to my core because I’m so OCD.

That’s a really good point. I wonder if that could make a difference. I also just read that adding cup to make it 5-7 cup on the prop will also reduce cavitation some of the 28s are known for. Unfortunately I just had the prop redone before reading this, of course.