Blisters vs bottom paint, how long is too long?

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LloydB

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Jan 15, 2006
927
Macgregor 22 Silverton
I saw this statement in an add: "Some bubbling on the bottom from being in the water a bit too long without bottom paint. The engine runs perfectly, low hours. The inte..." I thought the purpose of bottom paint was to prevent critters from growing.(mostly in salt water) I was surprised to see this on a 3 year old boat so am requesting some enlightenment and insight you may have.
Thanks for your response
 
Nov 6, 2006
10,093
Hunter 34 Mandeville Louisiana
Anti-fouling bottom paint does not protect the hull from blisters.. Blisters can happen in as little as three years.. not normal, but can happen.. Are ya sure it is in the fiberglass or is it the bottom paint ??
 
Nov 9, 2008
1,338
Pearson-O'Day 290 Portland Maine
If it's going to be steeped in water, salt or fresh, my understanding is that you need at least three coats of a good quality barrier paint to prevent osmosis. Once the barrier painting is done, a coat or two of anti-fouling is in order, depending on the type, to keep the critters from setting up shop. A boat, new or not, left in the water without some sort of protection is begging for blisters. (Sounds like an British steam punk band)
 
May 24, 2007
185
Beneteau 352 Milwaukee, WI
Bottom Paint - Different meaning to different people ...

"Bottom paint" is a generic term that, by itself, has little meaning.

As indicated above, gelcoat will eventually start to absorb moisture through osmosis and lead to blisters. This can happen in as little as one season or can take years. I used to have a MacGregor 26M and kept it on a mooring for one three-month season. The bottom looked and felt like the surface of a football. The entire bottom was covered with mini-blisters from below the waterline.

What I should have done (and eventually did) ...

Barrier coat with two-part epoxy paint such as Interlux Interprotect 2000e. Minimum four coats and typically applied from the boot stripe down. (Any surface that is in the water when the boat is at rest.) This coating is what actually seals the gelcoat and prevents osmosis.

Anti-fouling paint (often called bottom paint) is designed to keep critters from getting firmly attached to your hull. It does nothing to prevent blisters. What you use is dependent on where you keep your boat.

If you have a trailer sailor that gets pulled after every sailing, then you really don't need to do anything. Barrier coat and anti-fouling paint comes into play if you keep your boat in the water extended periods of time on a mooring or in a slip. "Extended periods" is a flexible term. The warmer the water the faster osmosis begins.

Make sense???
 
Aug 16, 2011
2
MacGregor 26M Naubinway, MI
Question about cost

Can you give me an idea of what it would cost to get the Interlux Interprotect system done on a Mac 26M at a local marina?

"Bottom paint" is a generic term that, by itself, has little meaning.

As indicated above, gelcoat will eventually start to absorb moisture through osmosis and lead to blisters. This can happen in as little as one season or can take years. I used to have a MacGregor 26M and kept it on a mooring for one three-month season. The bottom looked and felt like the surface of a football. The entire bottom was covered with mini-blisters from below the waterline.

What I should have done (and eventually did) ...

Barrier coat with two-part epoxy paint such as Interlux Interprotect 2000e. Minimum four coats and typically applied from the boot stripe down. (Any surface that is in the water when the boat is at rest.) This coating is what actually seals the gelcoat and prevents osmosis.

Anti-fouling paint (often called bottom paint) is designed to keep critters from getting firmly attached to your hull. It does nothing to prevent blisters. What you use is dependent on where you keep your boat.

If you have a trailer sailor that gets pulled after every sailing, then you really don't need to do anything. Barrier coat and anti-fouling paint comes into play if you keep your boat in the water extended periods of time on a mooring or in a slip. "Extended periods" is a flexible term. The warmer the water the faster osmosis begins.

Make sense???
 

KD3PC

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Sep 25, 2008
1,069
boatless rainbow Callao, VA
Can you give me an idea of what it would cost to get the Interlux Interprotect system done on a Mac 26M at a local marina?

once you have blisters, they need to be addressed before you proceed with the interprotect process described above. Cut them open, let them dry, fill with epoxy, fair and materials, haul and block, yard rent.

Ball park to have it done at a local marina is in the several thousand dollar range, as the materials and labor are fairly high. Various parts of the country have higher labor rates.

On the Chesapeake, to deal with the blisters you may have (not scaling the gelcoat off)individually and allowing them to dry and then fill with epoxy and then fair them for a 26' would be at least $1K depending on the number and mat damage to open them, most marinas will want 6-8 months or two seasons to dry them...Scaling the glass and replacing would cost more than the boat, and not guarantee they will not return. See the web at Hartges marina for some details of the process.

Interprotect is about $75 a gallon, marina price, factor in materials and labor for the 4 coats described and you are real close to another $2K.

Good bottom paint to adhere to the 2000e is +$100gallon marina prices, and labor will likely bring that piece to $1K, as most marinas who offer bottom paint by the foot, offer generic materials - not this good stuff.

Not sure why you would be getting blisters in the colder waters of MI, as it is most likely associated with warm water...unless McGregor is using less than stellar resins...still.
 
Sep 25, 2008
2,288
C30 Event Horizon Port Aransas
Can you give me an idea of what it would cost to get the Interlux Interprotect system done on a Mac 26M at a local marina?
How do you delete a post? I believe there used to be a button for it? I guess since I can't delete it I will just ask how.
 
Sep 15, 2009
6,243
S2 9.2a Fairhope Al
How do you delete a post? I believe there used to be a button for it? I guess since I can't delete it I will just ask how.

i think you go to the post you want to delete and push the edit button and take it out that way and leave a statement as to why or what ever ...

regards

woody
 
Aug 16, 2011
2
MacGregor 26M Naubinway, MI
Thanks for the info. We don't have blisters yet, but will be leaving the Mac in fresh water for at least a 3-4 month season next year. PM can't hurt. So far it looks good, but it has only been in since late June. 2K is what we were given as an estimate so I guess that goes with owning a boat. Yikes!
 
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