Hull bottom blisters- inland lake Bertram 42

That's a lot of big blisters. They're not going to get better, the longer you wait, the more damage they'll do. At a minimum you need to take the repair cost out of the purchase price. After you get these fixed, you'll probably want to put on an epoxy bottom coat to keep any more blisters from forming.

Get a hull survey if possible also.

Brian

The bottom paint is due. It's 4 years old. We normally do them in South Florida every 18 months or less. In the Great Lakes I would say 2 years out of a bottom job, maybe longer check around. But 4 years sounds like a long time.

As for the blisters, I would address Tennis ball sized and all golf ball sized soon, within the next year for sure. $40 a piece sounds like a fair price, maybe a little less if there are that many. I would have them ground when the boat is hauled for the winter and left open to dry during the entire winter, then in the spring, have them filled and several coats of a good barrier coating put on and then bottom paint. If the blisters were silver dollar sized, I'd say wait, but they sound larger......I wouldn't kill the sale, but I would ask for an adjustment from the seller.......maybe half.........or more if you can get it of the cost.......

I did a bottom peel on a 42' last year. It cost $12,000 which included everything, haul, pressure clean, peeling it, sitting out of the water for over a month, 6 coats of a barrier coat and 2 coats of micron csc bottom paint to give you an idea of cost. This was done in Ft. Lauderdale.

Amount of blisters per square foot would determine whether to peel them or grind them. If there are lots and lots of them, peeling is better and easier. On this particular boat it was only a few years old and had a pea sized blister, every square inch. So, there wasn't a way to just grind the blisters. With 75 blisters spread across a 42' hull, it's ok to grind them......

if you do not do a full peel you will make it much much worse..... see blisters are caused by osmosis........ SO they say bertrams do not blister but we know that is not true they just do not blister as bad as some other makes.... why u may ask????
bertrams were a gelcoated boat and used hi end gelcoat when building the boat it slowed down the osmosis, hatteres panted there boats and thay blisterd much worse....

it starts with the way a boat was built they cover the mold with gell coat and then 2 layers of mat the first layer makes up your chins on a bertram and there hallow. fallowed by 1 inch of roving by the keel and 1/2 inch near the hull side... now each lay up was layered in dry the covered with resin

so what happens to make a blister and why u have to do it all or nothing....

water is absorbed by the gelcoat it finds a dry fiber in the first layer of mat and like a wick the water is drawn thu to the other side now the water is more of an acid from its trip and will burn u if it leaks on you... the blister stops there see the acid is thicker and has more trouble wicking it also is localized and not as able to find a new dry fiber to travel further on + its under different pressure sandwiched in the glass than the entire hull pushing in to the water. blisters are never found in roving it can wick but will travel the whole path of the roving so lets say its just to strong... so u cut the blister out and u expose the edge and pocket to new osmosis... how to stop them peal all the mat crap off down to roving cover with roving or uniaxil and epoxy and you will have no blister worries ever...

I did a 35 bertram my self I know what in there... I have pitchers from the project cores from the thru hulls and this is common theory that can be seen all over the web....

now all that being true.. a bertram hull is up to 1 inch thick... so where is the blister going? NO WHERE. how is it going to get worse ??? whats the worse u get more they get bigger????? SO WHAT??? are they going to slow u down? NO. will one pop and sink your boat!!!! NO. or maybe all the blisters will join and the whole bottom layer of gelcoat and mat will fall off you boat at sea!!!!! ya that might happen but then a sea monster may also get you. bottom jobs are sold by boat yards and suckers who payed for them and guys like me who gave it a year or so of there life.... if were talking bertrams not cored boats or grady wight but bertram.... just leave it if she is from the 70'd she will out live u. if one pops peal it and fill it with epoxy and roving grind the paint off and epoxy the aria... and use your boat..... 10K to 12k buys a lot of fuel..

dont get me wrong it nice to have a fully restored bertram but just doing the bottom is a waste of time and $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

Though they sound quite large, the boat is at least 23 years old. If they haven't caused a problem, I wouldn't be too concerned. The bottom of your boat is solid glass, not cored. Blisters used to be a big issue. The last ten years or so they haven't created too many issues.