water line on C16 rudder blade

[jb]

Hi,

New CP- 16 owner refurbishing a neglected 96 model. Boat will be on a saltwater mooring and I'm trying to determine how much of the rudder blade ( original)  will be submersed, while in the raised position? There appears to be more pitted areas on the bottom 6-7 inches of the blade. Do you recommend, no paint,  standard bottom paint or the spray paint currently being used on O.B. drives. submersed?

thanks in advance for your response.

jb 

[MacGyver]

I highly reccomend using Interlux 2000
Sand with 80 grit or 60 to abrade the aluminum. Wash down with a solvent of choice to remove all sanding residue.
Apply 4 to 5 coats to the area below the pivot point that rotates into the casting/ housing.
When done, observe the time frame marked on Interlux 2000 barrier coat and paint with bottom paint of choice.

The Interlux 2000 will provide the necessary barrier so that the bottom paint doesn't interact (electrolysis) with the aluminum blade.

The key to a solid job will be prep work.

Mac

[carry-on]

Try to keep the aluminum blade out of the water when docked or moored. To accomplish this, I think you will not only raise the blade but also turn the tiller toward the outboard motor and secure the tiller to the stern cleat. This is your best chance for keeping the blade out of the water.

[wes]

Mac and JB - great advice from Mac as always, but please note that Interlux says the first coat of 2000e must be applied within 1 hour of when you sand the rudder. This is because bare aluminum begins to oxidize immediately after sanding.

Wes

[Pacman]

JB,

Mac, carry-on, and Wes have given excellent advice on this.

I would use Interprotect applied as Mac and Wes have recommended and, when you park the boat, if you follow carry-on's advice, the blade will be out of the water.

This is a great community.

Cheers,

Dave   

[jb]

Thanks for your responses, I hadn't given much thought to electrolysis. What are your thoughts on attaching a small zinc to the rudder blade?

jb

[Pacman]

I am not sure but I do know that it is standard practice to mount zincs on aluminum outboard and lower units.

Maybe that would be a good idea if the rudder is left in the down position and submerged in salt water.

The only small reservation I might have  is that any bumps on the rudder surface could add drag and/or disturb flow past the rudder.

I probably would not add a zinc if I could park the rudder with the blade out of the water as carry-on has recommended.

 

[Bob23]

jb:
   The rudder blade is easy to protect. The above advice is right on. The real problem, as I can personally attest is the rudder head and gudgeons. I moor my 23 in salt water so I can speak from experience- The lower nub on the gudgeon (the fitting bolted to the boat) was almost completely eaten away after a few years. I have since fitted 3 zincs to the boat: one to the blade, one to the rudder  head via the lower bolt and one to the gudgeon. The corrosion has slowed almost to a crawl and I can certainly improve my methods if I tried.
   Remember, there are 3 metals at work against you back there: aluminum castings and blades, bronze bushings inside both the head and gudgeon and stainless steel bolts. What a battery, huh?
Bob23

[jb]

Bob23, thanks for that interesting info.