Motor bolt hole question

3 Squids

3 Squids

Junior Member
I'm reading in multiple places people talking about drilling oversize holes for mounting the motor to the transom and then coating the holes with west system to prevent any water that makes it pass the LifeCaulk from getting into the wood. Anyone done this? Wondering how much bigger of a hole. 1/2" bolts so 17/32 or maybe 9/16? I'd like to do this to the blue boat before I hang the motor which is going to happen very shortly.
 
I don't know about anyone else, BUT I DO know tolerances etc. I know that the larger the hole, the greater the surface area and to me, the greater the surface area, the more likelyhood of water intrusion.

To my way of thinking the engine vibrates when it is running. No matter how smooth and quiet, no matter how great the anti-vibration system (if installed) it still vibrates. So if you have oversize holes that vibration is going to transfer from the engine, thru the bolts that the engine is hanging on and into the transom. If there is an oversized hole then the vibration must transfer thru the sealing medium first before entering the transom. So the larger the hole, the greater the chance of the vibrations, over time, destroying the sealing medium that it's passing through. It just doesn't sound like a good situation. Maybe it will last forever, maybe not.

Here's what I do. (Understand this is just my opinion, based on life experience and not some scientific answer)..... I take the holes that are there and I give them a very liberal coat of 3M 5200 sealant, inside and around the edges.. and I rub the stuff into the wood with a dowel, piece of scrap wood, whatever. Then I coat the underside of the bolt head and the shank of the bolt with the same sealant, slide the bolts through the holes, coat the area right around the bolts where they peek through the transom, touching the bolts with a continuous bead around the entire bolt, let it dry and then I hang the engine. This process insures that the bolt holes are 100% sealed against water intrusion.
If you feel that's not enough, then I would use some kind of epoxy liquid wood sealer https://www.jamestowndistributors.c...d=product_ad&gclid=CIyLw5GxjdMCFd5WDQodZ3oBfA that will be absorbed into the wood first, then after it dries do the process I described above.
 
I've always used large amounts of 5200 myself. I do my best to cover the inside of the hole before inserting the bolt, then I put a coat on the shoulder of the bolt before inserting it, the excess builds up under the bolt head sealing it water tight, then I put some around where the bolt exits the transom, and bolt the engine on. Has worked well for me so far.
 
That sounds like a very bad idea to me. I coat the hole good with 5200, let it dry, then 5200 again when I mount it. Epoxy would work well for the first step of sealing the hole, but the 5200 is flexible which is important.
 
squid, that transom looked like it had some work done to it. whats in the holes now. if its just bare wood. i'd probably take some epoxy and coat the wood, then 5200.

on smaller stuff like transducers, swim platforms, etc. I've done the over-drill, then completely fill hole with epoxy. after curing, drill pilot hole and mount screw.
 
I charge a whole lot of money to take motors off that people used 5200 to mount them. You should have to have a permit to buy that stuff. Life caulk works fine and isn't permanent. If you want to do it right, drill the hole over sized to fit a piece of 1/2 ID PVC, CPVC or PEX pipe. Coat the inside of the hole with epoxy, making sure to cover all exposed wood, coat the outside of teh tubing and insert it in the hole, wait till it cures and cut it off flush. Now when you mount the engine, only use regular silicone
 
Thanks for the feedback. The transom has bare wood in the hole now. But on a good note it's dry wood. Think I'll just get some 5200 and use an acid brush and brush it in the holes for a couple coats then just use LifeCaulk to seal the motor on. I've read horror stories about using 5200 to actually seal the motor on. And as much as I pull motors off that's the last thing I'll need.
 
I don't know to much about that but I do know that 5200 3 m is supposed to be permanent If and when you have to remove the engine it's going to be a real hard time your going to have I would not go by what I said but I would ask the heavy hitters and see what they suggest you to use
 
steplift20 said:
I don't know to much about that but I do know that 5200 3 m is supposed to be permanent If and when you have to remove the engine it's going to be a real hard time your going to have I would not go by what I said but I would ask the heavy hitters and see what they suggest you to use
Click to expand...

I'm thinking about putting a couple coats of 5200 in the bolt holes and letting it dry completely then seal the bolts with LifeCaulk.
 
I drilled my holes a 1/2 inch larger than my motors bolts. I then hotcoated the holes and taped one side closed. I then filled the hole with thickened resin and then glassed 2 patches of 1.5 csm on either side. The next day i drilled the holes to the actuall bolts size leaving 1/4 ring of glass around the bolt hole. Now this is the extreme end of the spectrum! And almost a little radical. Hot coat with West Systems 105 then use 3m 4200. I used 5200 on my first motor i mounted on my boat....when i took it off to put my suzuki on it pulled the paint and some gelcoat right off. I would west systems and 4200 if i did it again. If yo dont have west systems use a vinylester resin or a thinned polyester resin
 
I heart this thread. Not advocating 5200 ideas but deinstall damage pales in comparison to years worth of water intrusion. The worst that can be done is not sealing at all... Appreciate all the ideas as I am hoping to repower really soon.
 
Read my post again. What I said was I let the 5200 dry, THEN hang the engine. That way you get the sealing of the 5200, without the headaches it you need to repower. Unless you damage the threads on a bolt, the stainless bolts will last longer than the boat usually. This is a one and done solution.
 
Ive seen the outer skin of a transom pulled off of a boat while trying to remove an engine that was installed with 5200, it destroyed a solid transom. 5200 stills cures and adheres for weeks after its installed. Life Caulk is rated for under water line use. You need a sealant, not an adhesive(5200)
 
Ok so I've kinda combined everyone's advice. Last night I used acid brushes and brushed a liberal amount of 5200 in the transom holes then applied a good coat on the bolt shanks and inserted the bolts through the transom. I also put a bead around the outside of the bolt holes and wiped it around the bolt real good. Sure enough today then babies are stuck in there good. Now I plan on doing a good bead of LifeCaulk around the bolts when I set the motor. I feel this should suffice.
 
Question about this 5200 stuff. Never used it before. I brushed it on last Thursday evening and inserted the bolts. Came out Sat. and hung the motor and the stuff was still wet. A little stick but still could wipe right off. It's now Tuesday and the stuff is still not dry. Is this normal? Seems to be more tacky then Sat. but still I can wipe it right off. Bought it from West Marine so I figure they have a pretty fresh stock.
 
3 Squids said:
Question about this 5200 stuff. Never used it before. I brushed it on last Thursday evening and inserted the bolts. Came out Sat. and hung the motor and the stuff was still wet. A little stick but still could wipe right off. It's now Tuesday and the stuff is still not dry. Is this normal? Seems to be more tacky then Sat. but still I can wipe it right off. Bought it from West Marine so I figure they have a pretty fresh stock.
Click to expand...

Is it the regular 5200 or the 5200 fast cure? The fast cure usually takes about 2-3 days to harden. I've never used the regular so can't provide any info on it. As to Spareparts' comment about 5200 still hardening after weeks, that sounds like what you may be experiencing.

A quick comment about that by the way. If you use my method and you're still worried about an engine adhering to the boat... like anything else in this word, use the KISS principal. Instead of trying all kinds of different materials, methods, etc... just go into your kitchen pantry, get out the roll of plastic wrap that you use for sealing bowls of leftover food, take it to the boat, cut a roughly 3" x 3" square, punch a hole in the middle slightly smaller than the bolt diameter and slide it down over the bolt and up against the hull and any sealant that happens to be there. The (obvious) goal is to provide a thin membrane between the engine and the sealant when you hang the engine. That way when you remove the engine there's no chance of it being stuck to the sealant since it never touched the sealant in the first place. K.I.S.S. Keep It Simple Stupid :head:
 
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Took 9 days for my last batch of 5200 to go off. The fast cure as stated 2 or 3 days....regular cure says 7 days on the caulk tube in ideal conditions.
 
It's not the fast cure. I find it crazy it's still wet. I've read somewhere else misting it with water helps so I'll try that. Hoping it will be all cured by this weekend cuz I'm itching to take this baby out.
 
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