repainting Thompson, below waterline

[bigfootnampa]

I am looking for coatings to repaint the hull of a thompson 19.5 foot outboard ski-boat. Does anyone out there have some favorites that they want to share? I am also open to advice as to prep techniques and protocols. I am a skilled finisher with HVLP spray equipment available (I have not done many such boat hull recoatings thgough). This boat will be trailered and so, only wet on weekends. It's a 40 year old hull but has only slight peeling and minimal cracking.

[marshmat]

I'm an Interlux fan, myself. Put their lowest-grade enamel on my runabout five seasons ago and it still looks shiny as new. Their 1- and 2-part polyurethanes are great for topsides and trailer boats. Look at Awlgrip's stuff too, it's similar. For the bottom, you can use the same paint if it's trailered; ask your dealer for an appropriate antifouling if it's left in water.

Most boat paints (for topsides) are rolled on and brush-tipped. Since you have spray experience you may want to do this, but be warned that urethane is hard to spray. For the bottom, just any plain old roller works.

Prep tips: The usual sanding (80-160-240 is a common one, can skip the 80 if it's already OK). Then solvent wash, either acetone or paint company's magic liquid, to get the wax out of the surface of the fibreglass or old coatings. Spray with water. Any beading at all, repeat the solvent wash. You usually have to do this several times. Very important to get ALL the wax out and use a suitable primer, or the paint will fail. Most paint makers give you a little booklet when you buy paint listing exactly what to do for each type of hull material.

[bigfootnampa]

Thanks Matt;
I have talked to an Interlux dealer here who reccommends that I contact their reps directly for the latest info and strategy. I guess that I will try that. I haven't owned a boat of this type before and was a bit dissappointed at the amount of water taken on over 4 to 5 hours in the water Monday (at least several hundred gallons). If I hadn't had the foresight to jury rig a temporary bilge pump the cruise might have been much shorter. It is possible that I have some repairs to do before painting begins. The stem appears to have a crack or break that I may need to fix and I am guessing that there may be more, when I get things cleaned up and sanded back. It appears that my mechanic must have missed something enginewise as it developed a severe miss at high power. This was especially distressing because of the swift approach of a severe squall that we had hoped to outrun. The fact that the canvas tops have been saved for a future project made the engine problems and the squall's approach a bit daunting. In the end everyones maritime enthusiasm got severely dampened. We did manage to find the ramp through the deluge and very slowly limped in about the time the squall passed over. All in all a forceful lesson about having your ship shipshape even for simple forays.

[PAR]

I work on this type of boat all the time and you should have a boat carpenter take a look. I'll bet you see small cracks along the plank to stem seam, along the bottom seam at the garboard and around the transom edge too. That much water means something has failed, maybe a stopwater in the keel or bedding on a thru hull or keel bolt as well as the planking seams.

Is this the lapped hull with the big, wide bottom planks? I'll also bet it's the thru bolts holding the gripe to the stem and keel. They get loose with age and use. This permits the stem to work back and forth, which loosens the other fasteners. You need a pro to look her over and they need to be familiar with the type of construction, the manufacture and era built. A boat can be screwed up easily with ill thought out repairs on a method they aren't accustomed with, trust me.