A zinc fitting question

[senormechanico]

I've realigned the engine, checked the shaft for trueness etc., but I still have vibration. That's a subject for a different thread...


Steve B.

[Ex-Calif]

How about trimming the end of the housing that is attached to the skeg? I don't know how much meat is there but that could be a more permanent fix.

Or looking at it maybe a bit from the prop and a bit from the housing. The prop hub looks pretty robust.

[bmiller]

Here is the protype cut from an old zinc. I was checking to see if there is enough material left after fitting to support the nut/bolt without coming apart. The next one will be turned on a lathe.

[senormechanico]

The thrust from the prop will push the shaft forward against the motor mounts. This will wear away a bunch of the zinc against the cutless bearing. It will wear according to the throttle setting. More throttle= more thrust= more wear.

Whether the zinc or the cutless will wear the most is the question.
Either result is not good.

Steve B.

[Sandero]

I have a similar installation and I have the donut ground down about an 1/8" and this allows for the prop pulling forward. Here you can see it before the zinc is installed.

I suppose the test is how much zinc is left when you haul out. For me the boat is in the water at least 11 months, 4 of it in a marina, 7 on a mooring and I always have some zinc left. I am assuming that IT is taking the "hit" and not sharing it with the other metals. Am I safe in that assumption?

jef
sv shiva

[Alan Wheeler]

bmiller, with all due respect, mate thats ugly ;-) It must be causing a lot of turbulence over the blades. Plus the gap between blad and skeg is just too small sorry. It's going to cause problems.

Jef... Mate!! that blades got a heck of a lot of pitch on it. You sure you didn't bolt on an aeroplane prop by mistake??:-)

[Sandero]

Alan,

Negative, That's the prop the boat came with in 1985 (MD17D). I don't know the prop specs, but it performs quite well in forward and reverse. However, I've not seen any similar in the yard.

jef
sv shiva

[JohnnyC]

Thanks from here as well Steve.
That looks like a much better solution for those of us with props in small apertures than the prop nut anode from defender! Yours looks like it will stay in place beautifully.
John

[ronbo1]

Wheels and Steve B make a point worth repeating. The gap between prop and skeg is too narrow. When prop is driving forward the gap narrows due to the flexible engine mounts and the flexible coupling(if you have one). Metal grinding on metal is not good.

Also, prop nuts are on in wrong sequence. Perhaps for another thread...

Ronbo

[fstbttms]

Originally Posted by Sailorguy

This is the URL to the propeller nut zinc referred to:

BoatZincs.com (978-841-9978) - Discount Zinc Anodes

This is not a good solution. Too little zinc. If you are going to go with a prop zinc, use this style:

[GordMay]

Originally Posted by ronbo1

Also, prop nuts are on in wrong sequence. Perhaps for another thread...
Ronbo

We’ve had a previous (interesting & informative) discussion regarding “Jam Nuts”
Goto:
http://www.cruisersforum.com/forums/...nuts-8891.html

[Alan Wheeler]

Negative, That's the prop the boat came with in 1985

No sorry, I meant the shaft anode looked ugly. Sitting up proud from the prop boss and aft bearing like that, must create turbulence that would then flow over the blade of the prop.

Personly, I think this is install is an excellent candidate for a decent anode to be placed on the major metal area(maybe rudder if it is steel and I assume one has already been installed as such) and a shaft brush installed on the shaft in the engine room. Let the one major anode do the work. I have always found that scenario much more reliable.

[bmiller]

Originally Posted by Alan Wheeler

bmiller, with all due respect, mate thats ugly ;-)

Yes it is. I hacked away at that one with a sawzall just to see if there would be enough material left before I went to the bother of putting one in a lathe. I thought that was enough clearance for water into the cutlass but from all the info here it appears not. Didn't realize how much forward travel of the shaft there could be.