Bunk Lag Bolts & 3M 4200??

I will be replacing my trailer bunks soon. I wont have the luxury of a place to leave the boat off the trailer except at a ramp somewhere so I will have to prefab everything except drilling the holes and screwing them down with lag screws. Is it a good idea to put some 3M 4200 on the lag bolt holes/screws? Will it help keep them from backing out and slow down water penetration? Has anybody tried this or have any experience with this?

If you are using wood, you could use a little 4200, but it won't slow water intrusion. If you know you are keeping the boat long term, order Trex and use it instead of wood. No water intrusion ever. A little 100% silicone will help to keep the bolts from falling out if the wood goes bad and the threads loose their grip.

Thanks for the suggestion but that stuff sounds a little expensive for my taste. I would also be a little worried about linear strength without additional supports and fastener integrity.

Use a 5/16" lag in replacements bunks. When they start to back out years later just replace with 3/8".

Dang, my pea brain never considered that. That 1/8" for the screw to wallow around in the support hole would serve as a good indicator that it's loosening up.
I guess the question then is will that adhesive cause a bigger chunk of wood to come out when they do start loosening?
I have learned that those bad bunks can sneak up on you even when you check them all the time. I'll be using the ice pick check from now on when they start getting some age on them.

Thanks

I predrilled mine and used a countersink bit to allow the bolts to sit below the sliding surface. I also used stainless steel bolts, washers, locks, and nuts. Problem solved.

I just hope they don't ever come loose....could be bad for the boat....

I used the same process to install my Ultimate Bunk Boards.

That would be my preferred method. Just not sure that when I get to the boat ramp all the bolts will line up. Hard to redo after the carpet is all glued and stapled. I'll be giving that a close look when I get my boat home from the shop tomorrow.

Had holes drilled in heads of lag bolts and safety wired them to vertical bunk support brackets. They cannot loosen or come out.

If you don't get the boat off of the trailer to do this you are setting yourself up for an exercise in futility. You can not measure accurately enough to free drill the holes and have them line up. You'll have to lay the old boards on top of the new ones and use that as a template for drilling.

[/quote] If you don't get the boat off of the trailer to do this you are setting yourself up for an exercise in futility. You can not measure accurately enough to free drill the holes and have them line up. You'll have to lay the old boards on top of the new ones and use that as a template for drilling. [/quote]

Yep. Took me about 2 seconds to figure that out. It's kind of a dilemma since I intend on putting some glue on the carpet which has to have some time to dry and I don't plan on spending the night at no boat ramp. Once the old bunks come off, the new ones have to go back on. I think I'll just go with the 5/16" lags and then go to the 3/8" when they loosen up. By that time they'll probably be rotted out again. Maybe try a little 4200 to slow things down a little.

Thanks for the suggestions

you could do the bolts at the ramp. Just do not glue the carpet. I never have glued mine. On my 3 set of bunks and the carpet and or wood will wear out before the staples do.

my idea was to drill/countersink the wood, treat the bolt hole area with epoxy/acetone mix to absorb into the wood and use stainless blind nuts to bolt it down from the bottom, if anything else, use the epoxy/acetone mix in the fresh drilled lag bolt holes, of course this will add time to the repair but i had no issues jacking the boat up off the trailer one side at a time

stainless carriage bolts, hardware... but ya gotta be good.

Thanks for all the tips guys.
I got all my materials today. Stainless nuts, bolts, washers and staples. Going to use bondo to fill up the screw holes. It should dry fast enough while I do some fishing.
Going to have to work one bunk up to be sure I'm not going to need glue with this crappy "Deluxe Marine Bunk Carpet" that I ordered. The stuff doesn't even look like carpet to me and it doesn't have much of a backing on it at all. It came highly recommended and good reviews though so I think its all gonna be good. I have the one bunk that came off at Falcon to use as a template for holes. I should be able to get to the lake somewhere and get it done first part of next week. And get a little fishing in too.

[/quote]you could do the bolts at the ramp. Just do not glue the carpet. I never have glued mine. On my 3 set of bunks and the carpet and or wood will wear out before the staples do. [/quote]

That glued on carpet on the bunk that came loose was a real PITA to get off without tearing it up since I couldn't find any carpet in Zapata to work up a replacement to keep me going.

Who would have ever thought there would be so many lessons to learn over stupid trailer bunks.

I love my Ultimate Bunk Boards. I'll never mess with carpet and staples again.

I just prefer a little padding next my fiberglass even though it probably doesn't help anything. Six of those would run what, about $800. Probably not a bad deal if you know your going to have the boat for 15 years.

why not take the boat/new boards to the ramp.
launch
take old boards off and predrill new for drop thru carriage bolts, reinstall old boards, go home and carpet the new with carriage bolts already installed, epoxy the heads before carpet is put on.


next week go back to ramp and install new boards.

oh, and use pressure treated rated for ground contact, you will not outlive it.

Those old bunks are just hanging on by a thread. Bolts all rusted with hardly any threads left. I wish I lived 10 minutes from the lake instead of 45. Any way, It's gonna get done tomorrow. A couple hours at the ramp replacing bunks. About 4 or 5 hours fishing while it dries and good to go.

I did find treated ground contact at Home Depot.