Below waterline primer

[chille51]

I recently patched a couple of old screw holes in my transom with West Six10 epoxy. They are small holes so my plan was to try and find a paint that matches as best I can, and I assumed I needed to use a primer first. I asked for advice at Industrial Plastics here in Nanaimo and went with what they suggested, which was Interlux Pre-Kote. Didn't really question the choice at the time, they usually know what they are talking about. However I was going to apply it yesterday and when I read the label, it is quite clearly intended for above the water line applications only. Looking at the Interlux website it seems like InterProtect 2000E might be the better choice. Or maybe I am over thinking things as usual, and there is a simpler option?

What would those with more experience use, both for paint and primer over West Six10? Keeping in mind we're talking about a couple of small holes, not an entire transom recoat. They don't even look that bad honestly, but I understand the epoxy is probably not UV stable.

*Edit - this is a fibreglass hull, in case that wasn't already obvious.

 

[BC Coast Pilot]

I recently patched a couple of old screw holes in my transom with West Six10 epoxy. They are small holes so my plan was to try and find a paint that matches as best I can, and I assumed I needed to use a primer first. I asked for advice at Industrial Plastics here in Nanaimo and went with what they suggested, which was Interlux Pre-Kote. Didn't really question the choice at the time, they usually know what they are talking about. However I was going to apply it yesterday and when I read the label, it is quite clearly intended for above the water line applications only. Looking at the Interlux website it seems like InterProtect 2000E might be the better choice. Or maybe I am over thinking things as usual, and there is a simpler option?

What would those with more experience use, both for paint and primer over West Six10? Keeping in mind we're talking about a couple of small holes, not an entire transom recoat. They don't even look that bad honestly, but I understand the epoxy is probably not UV stable.

*Edit - this is a fibreglass hull, in case that wasn't already obvious.

If its a gelcoat finish, try and stick with polyester resin based products instead of switching to epoxy.
Awlgrip may be your solution but may be cheaper to grind back the epoxy and go with polyester resin based filler and gelcoat match

 

[Rayvon]

If its a gelcoat finish, try and stick with polyester resin based products instead of switching to epoxy.
Awlgrip may be your solution but may be cheaper to grind back the epoxy and go with polyester resin based filler and gelcoat match

That's more or less what I do.I drill out the holes to dry wood,countersink the holes,use a syringe to fill the hole w/epoxy ,tape over it so it doesn't run out,let set overnight.Epoxy and polyester don't like each other,so I grind about a 2" circle + or_ 1/8" deep and fiberglass till flush.Then sand just below surface and fill w/gelcoat to match.If you try to gelcoat over the epoxy it may not adhere,so I go the long route.Probably overkill,but it works.

 

[tubber]

Rayvon knows. However, I re-gelcoated much of my old hull, but on the transom there were so many old époxy screw patches it wouldn't cure in a few spots. I sanded that section and sprayed a few coats with a can of Krylon from Lordco that matched the colour.No primer. It's been there 4 years. Part of it is under water Trailer boat.

 

[smp747]

I've been looking for similar information
The one thing I'll add from what I've read (don't take my post as knowledge, as I'm just learning) is to make sure you use unwaxed polyurethane gelcoat as you can layer it consecutively whereas waxed you cannot.

A good video I just watched on the topic was this one..

 

[Rayvon]

You can actually,the wax comes to the surface to allow the gelcoat to cure without being sticky.You just need to wipe it down with acetone and sand before the next coat.I always buy unwaxed and add air dry (liquid wax) when needed,normally the last coat.This guy do's great video's for Total Boat,a little long winded for my taste,but knows much more than me.

 

[chille51]

Rayvon knows. However, I re-gelcoated much of my old hull, but on the transom there were so many old époxy screw patches it wouldn't cure in a few spots. I sanded that section and sprayed a few coats with a can of Krylon from Lordco that matched the colour.No primer. It's been there 4 years. Part of it is under water Trailer boat.

I did find a can of Krylon that looks like a pretty close match. Sprayed some on a scrap of starboard and will take a closer look in the daylight before making any commitments.

 

[myles]

A little bit of misinformation here. You are correct you absolutely should use epoxy products to fill holes below the water line. Epoxy has much better physical properties than polyester. Since the repair is below the water line you can just cover the repair with bottom paint afterward who cares about gelcoat?

If you need gelcoat to stick to the epoxy repair then I know 2 surefire options that will work every time. Maybe you dont have bottom paint on the boat because it's stored on a trailer.. let me explain

#1 Get some nylon cloth (peel ply) I'm sure a fabric store has something with 100% nylon. Once the epoxy has been applied in a thickened state, put a layer of the nylon cloth over the repair pressing and smoothing it so the resin from the epoxy wets out the cloth like a fiberglass layup. you could tape over this or just leave it. Make sure your mixture is thick enough that it won't sag. once cured the nylon peels off leaving a nice texturized surface that can be immediately coated with gel coat or sanded down. If you want a nice finish sanding is a good option before gel. The KEY part is the Amine "blush" has now been removed by the peel-ply nylon that you throw away. This is not magic people, it's just science.

#2 method do the same to repair the site as above but skip the nylon and wait for the epoxy to cure then get yourself warm soapy water then scrub the repair site a few times with green scotch bright and let dry. Make sure to wash the soapiness off each time. The repair should go from a shiny almost greasy look to a dull haze. This removes the amine blush which is the thing that impedes the polyester from curing. then you can cure poly or whatever you want over the repair.

A lot of guys use duraglass etc, which is fine but its not waterproof and not as strong or tough as epoxy. If i did duraglass to fill holes i would expect more shrinkage, and have to coat over the repair with interprotect to ensure the repair is waterproof. Remember these repairs rely on physical bonding properties not chemical ones like you get in a new boat layup in the factory. That's why epoxy always wins for below-water line repairs or highly structural ones above the water line.

Epoxy and poly play nice you just need to know how to play the game.

 

[chille51]

A little bit of misinformation here. You are correct you absolutely should use epoxy products to fill holes below the water line. Epoxy has much better physical properties than polyester. Since the repair is below the water line you can just cover the repair with bottom paint afterward who cares about gelcoat?

If you need gelcoat to stick to the epoxy repair then I know 2 surefire options that will work every time. Maybe you dont have bottom paint on the boat because it's stored on a trailer.. let me explain

#1 Get some nylon cloth (peel ply) I'm sure a fabric store has something with 100% nylon. Once the epoxy has been applied in a thickened state, put a layer of the nylon cloth over the repair pressing and smoothing it so the resin from the epoxy wets out the cloth like a fiberglass layup. you could tape over this or just leave it. Make sure your mixture is thick enough that it won't sag. once cured the nylon peels off leaving a nice texturized surface that can be immediately coated with gel coat or sanded down. If you want a nice finish sanding is a good option before gel. The KEY part is the Amine "blush" has now been removed by the peel-ply nylon that you throw away. This is not magic people, it's just science.

#2 method do the same to repair the site as above but skip the nylon and wait for the epoxy to cure then get yourself warm soapy water then scrub the repair site a few times with green scotch bright and let dry. Make sure to wash the soapiness off each time. The repair should go from a shiny almost greasy look to a dull haze. This removes the amine blush which is the thing that impedes the polyester from curing. then you can cure poly or whatever you want over the repair.

A lot of guys use duraglass etc, which is fine but its not waterproof and not as strong or tough as epoxy. If i did duraglass to fill holes i would expect more shrinkage, and have to coat over the repair with interprotect to ensure the repair is waterproof. Remember these repairs rely on physical bonding properties not chemical ones like you get in a new boat layup in the factory. That's why epoxy always wins for below-water line repairs or highly structural ones above the water line.

Epoxy and poly play nice you just need to know how to play the game.

Thanks for the detailed breakdown, and yes given the location of these holes I have prioritized integrity of the repair over aesthetics. Hence the epoxy, and hence my original question re potentially just painting them. I do want to learn the basics of glassing and gel coating, but not sure the transom is where I want to do my experimenting. I have plenty of holes in the gunnels and the dash from the previous owner that I need to patch mostly for looks, so I'll probably try my hand at the more nuanced techniques there. Sounds counter intuitive I know, since those spots are more visible - but other than having to look at and be annoyed by a less than perfect repair, the stakes are lower.

 

[myles]

Thanks for the detailed breakdown, and yes given the location of these holes I have prioritized integrity of the repair over aesthetics. Hence the epoxy, and hence my original question re potentially just painting them. I do want to learn the basics of glassing and gel coating, but not sure the transom is where I want to do my experimenting. I have plenty of holes in the gunnels and the dash from the previous owner that I need to patch mostly for looks, so I'll probably try my hand at the more nuanced techniques there. Sounds counter intuitive I know, since those spots are more visible - but other than having to look at and be annoyed by a less than perfect repair, the stakes are lower.

Above water line stuff and cosmetics are much more difficult to repair but just need to know a few tricks and you can get really satisfying results.

Colour matching the gel takes skill - guys out there will mix you up a gal for a fee if you want it to match perfect.

For all that non structural stuff above water line nothing wrong with using polyester. Just try and avoid filling everything with mud (duraglass and fillers) its very tempting to do... Use glass as mush as possible it's going to shrink a lot less over time. I know this from experience and doing it the wrong way.

Pretty low risk stuff play around and learn and if you make a mistake just grind it out and start again. If you have a lot of repairs and it's not going to be easy to sand and polish the sprayed gel because you have lots of corners and curves then just sand the whole part and go over to a paint product with primer. The roll additives now are very good get spray results with much lower skill required. Alex seal paint is what I've recently used.