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Excessive Bottom Paint – Does it Make a Difference? This article will focus on a series of questions I received from a reader in Jacksonville, FL, after reading the articles on blisters in the November issue. On this boat all the bottom paint has been removed, and the water barrier (Interprotect 2000) applied.

“Tom, I read your article in SOUTHWINDS on blisters that brought up a couple of questions. I have a 1971 Morgan 30 that has about eight or nine layers of bottom paint. The bottom has no blisters. I like to race the boat in cruising class and nonspin regattas. I plan to take it out and redo the bottom in a couple of months. I was thinking of taking all the old paint off the gel coat and repainting it. If I do this, will it have the potential to get blisters? I want to have a clean smooth bottom for racing, but don’t want to create problems with blisters or cracks in the hull. Is it wise to take all the paint off? What would be the best paint sequence to protect the bottom? Barrier coat/paint/sealant? I was thinking of doing two barrier coats, then two paint coats.”

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January 2010


Thanks for the great question. You have a very well-built boat. It is from the Charlie Morgan era and pre-OPEC oil crisis, so you have one of the sturdiest hulls put out by the St. Pete boat factories of that time. Charlie and another prominent builder by the name of Ted Irwin dominated the Southeast building industry during those years. Charlie went the sturdy cruiser route and Ted Irwin, who was a world-class yacht racer, went the race horse. I have owned both a Morgan and an Irwin, and both are great boats within their design intentions. Since you want to improve performance, the first area we need to address is weight. One gallon of bottom paint weights approximately 35 pounds and your size boat would normally take about two gallons of paint per bottom job. With 8 to 10 bottom jobs’ worth of paint, you have over 600 pounds of unneeded weight just in exhausted bottom paint alone. Reducing that weight by removing the excessive bottom paint should help you gain some speed. In previous articles, I discussed the osmotic nature of gel coat. Like gel coat, bottom paint is also porous. It is intended as an anti-foulant, not a barrier coat, so it won’t prevent blister formation. Preventing water from coming into contact with the resins under the gel coat is the only way to prevent blister formation due to the boat sitting in the water. Don’t forget, water in the bilge can also cause blisters so it is important to keep your bilge dry and paint it with an epoxy barrier coat like Bilgecoat. You are in for a dirty job. With that much paint, it will take a huge effort to grind/sand it all down to the gel coat. If you do it yourself, it will save you a lot of money. There are a few things you can do to help things along. First, pressure-wash the bottom with a 3500-psi pressure washer. Most yards have one that you can rent or you can pay the staff to do the task. Try to knock off as much of the brittle paint as possible. You will need to put down some plastic tarps to catch as much of the by-product as possible.