Mast Corrosion

[Mirage85]

Hey, I have a Pearson 303, 1985 and have just had it hauled for the first time since purchasing it. I had a marine surveyor go thru it to make me aware of issues. The only really big problem noted was the electrolysis of the mast at the base. The mast is becoming pitted and corrosion is working on it. He suggested I have the mast taken off the boat, cut off the pitted portion and have a new 6-8 inch section welded on. He stated I would probably need to have a new plate prefabed since he did not think I could get one to replace it that attaches to the hull. In the meantime I am to scrub the area, dry it out and put some epoxy on it to slow down the corrosion.
1. Have you experienced anything like this with your boat and if so how or what have you done?
2. Do you know of a source for the mast plate?

 

[Tim R.]

I had the same problem with my Perason 28-1. I cut 4 inches off and then built up a 4x4 aluminum base under the step. See my web page below for photos.

Call Rudy at D&R Marine. He is their Pearson expert and should be able to help you find a step if he does not have one.

http://www.drmarine.com/

 

[sailingdog]

This is a pretty common problem for keel-stepped masts, especially in boats with chronically wet bilges. The solutiion is pretty standard as well—cutting off a section of the bottom of the mast, replacing the mast base, and then raising the mast step an amount equal to what the mast was shortened by.

However, I would recommend making the mast step out of fiberglass and aluminum, to reduce any future problems. The bottom section, which will probably be exposed to the most water, should be fiberglass, with the top section, that contacts the mast foot, made of aluminum.

 

[Rich (P303)]

Hey, I have a Pearson 303, 1985 and have just had it hauled for the first time since purchasing it. I had a marine surveyor go thru it to make me aware of issues. The only really big problem noted was the electrolysis of the mast at the base. The mast is becoming pitted and corrosion is working on it. He suggested I have the mast taken off the boat, cut off the pitted portion and have a new 6-8 inch section welded on. He stated I would probably need to have a new plate prefabed since he did not think I could get one to replace it that attaches to the hull. In the meantime I am to scrub the area, dry it out and put some epoxy on it to slow down the corrosion.
1. Have you experienced anything like this with your boat and if so how or what have you done?
2. Do you know of a source for the mast plate?

Wow... Finally a subject I am an expert in! I have a P303 #121... and I just replaced mine. Once I got the mast base out... it was ALOT worse than it looked. It attaches with 4 lag bolts... sits in 1'4 of salt water 24/7.

I made a template out of some stiff paper... just in case the original one got destroyed. Took the old one and gave it to a family member who works at a place that works with aluminum. He made an exact replica out of 1/4 aluminum. After the second try... it fit! It didn't cost me anything... however, I probably owe him one.

It took 25 years for the base to develop that problem... I figure I won't have to worry about that again. I guess if I was 5 years old... I would have coated the new part with some epoxy.

The base of my mast was O.K.... so I can't help you there. I would opt to cutting the minimal amount off the base of your mast... and possibly building the base back up if possible.

Enjoy your new boat!

 

[sailaway78]

Mast Base

I have just finished repairing the exact same problem, on an S37. Mine was pretty bad for about three inches of the bottom. The base and mast step were fine. What I did was cut three inches off the base of the mast. I made a spacer/riser, from pressure treated 2 x 10. Epoxied heavily. Then put a 1/4" aluminum plate on top of that, with the mast step on top of the plate. I planned on making the spacer out of aluminum, but machine shops here are in very short supply, and rather expensive. Best deal I could find on having a spacer made up, was over 400 bucks. I wouldn't recommend sitting the mast base directly on the wooden spacer, but with a 1/4" plate, it works fine.

 

[Skipper]

Zinc

I am knowledgable in many categories.
This is not one of them.

What if someone has this mast base corrosion problem and jams an outboard zink in between the mast base and deck plate on the side?

Is it electrolosis corrosion or salt related?

 

[sailingdog]

In a lot of cases, the mast corrodes from the inside out, since it is water that is coming down the mast that is causing the problem. This is especially the case when the mast foot is not the same grade of aluminum as the mast or is stainless steel.

 

[Ross]

If it were mine I would build up the mast step with black locust. Black locust fence posts last for 50 years in Maryland's 45 inches of rain soil here. It is almost as hard as aluminum.

 

[Rich (P303)]

I am knowledgable in many categories.
This is not one of them.

What if someone has this mast base corrosion problem and jams an outboard zink in between the mast base and deck plate on the side?

Is it electrolosis corrosion or salt related?

I thought of the same thing. My 4 lag bolts that hold the mast base down were stainless. I put a rubber washer between the two.

It couldn't hurt to fasten a zinc somehow to the mast base! Very easy to do... just tap a hole... and screw it in.

Thanks for the idea.

 

[sailingdog]

Rich-

If the corrosion was from the inside out, it would be far better to add drainage holes to the bottom of the mast, rather than a zinc. Is your bilge normally dry, or is it always wet? If it is normally dry, the chances that the corrosion was caused by water inside the mast is much higher. Adding a zinc won't affect that—adding drain holes will.

If your bilge is normally wet enough to cause this kind of corrosion issue with the mast step, maybe looking for and closing off the leaks into the bilge would be a better alternative in the long run than using a zinc.