Outdrive surround repair

[Topknotrob]

Hi all


I am currently looking to temporarily cover the outdrive holes in my transom. I have 2no 6mm 316 stainless plates that I am going to bolt on until I have refurbished the legs and come out of the water again in the spring.*

Unfortunately the hull has been sheathed badly (imho), with polyester and csm and was peeling away around the edges of the outdrive holes. *Because of this I decided to feather it back exposing the original mat, but leaving the original gel coat directly underneath where the plates will go - as this is a flat smooth surface for which to seal against. * I was then thinking about laying some epoxy and cloth over the joint between the original resin and the sheathing to prevent any water ingress/osmosis behind it.


My questions are:-


1. Should I sand back the gelcoat behind where the plates are and epoxy the whole areas? *

If so:*

-What mat and how many layers?*

-Would this then need filling and sanding smooth so to give a better seal?


2. I intend to bolt together using the rubber gaskets and 3M 5200 sealant in and around each bolt hole.*

-Should I use vaseline on each side of the gasket, or smear some 5200 on instead?

[Sailmonkey]

You want to take this off in the spring?

DO NOT USE 5200!!!!

I also don’t understand why the sheathing is there.

Use something way less aggressive to seal with like boat life life calk polysulfide or even 3m 4000.....but not 5200.

I also see no reason to coat over the gelcoat with anything.

[tkeithlu]

A simple soft gasket will do. You've got a smooth surface, a SS plate, and multiple bolts. There is only a few inches of water pressure involved, way less than one PSI. Use Butyl tape or a soft gasket material, and if that does not appear to seal well, some silicone sealant.

Sailmonkey's NO! to 3M 5200 is important. 5200 is for permanent assembly, or situations where you are willing to grind/drill the stuff out if you ever have to, but you hope that you won't. Cured, it is one step short of being epoxy.

General impression: You may be over-thinking a pretty simple situation. Good luck with it.

[Spot]

Does the boat really need to be splashed before the outdrives can be repaired and re-installed? Having a boat in the water with patches and no motive power seems like trouble in of itself.

PS- I used to have a Merc 140 I/O and had to pull the outdrive and unmount and hoist the engine to get at the coupler, then all back, more than once-so I have felt your pain so to speak.

[Topknotrob]

Originally Posted by Spot

Does the boat really need to be splashed before the outdrives can be repaired and re-installed? Having a boat in the water with patches and no motive power seems like trouble in of itself.

PS- I used to have a Merc 140 I/O and had to pull the outdrive and unmount and hoist the engine to get at the coupler, then all back, more than once-so I have felt your pain so to speak.

It's a friends boat and unfortunately he doesn't have the funds to do the legs. What started as a minor lift out for basic remedial work has turned into a full blown restoration as we have uncovered some dodgy repairs etc.
Both engines were seized, but I manage to free them with some diesel and a lot of patience! One of the legs had the hose clip on the bellows rusted in two so water has gotten into that drive.. With this in mind, at least one of them will need a total overhaul and my time is taken up on the boat. We did get quotes of around 2k per leg for professional rebuild, but this would eat into the budget for other more important work.

Would 2 temporary plates really be much different to bolting on the outdrive itself in terms of water ingress?

[Topknotrob]

Originally Posted by Sailmonkey

You want to take this off in the spring?

DO NOT USE 5200!!!!

I also don’t understand why the sheathing is there.

Use something way less aggressive to seal with like boat life life calk polysulfide or even 3m 4000.....but not 5200.

I also see no reason to coat over the gelcoat with anything.

Thanks for this Sailmonkey.

I believe the sheathing may have been a cheap shot attempt at osmosis repair, although I'm not 100% sure. The only reason I was wondering about sanding off the rest of the gelcoat in the area was because it has a few cracks and star crazes and I didn't want to rent the risk of water ingress to the original resin and mat.

Ok, I think 5200 was a bad call then! Will it need to be a sealant that sets, or could I use a cheap butyl type (like gutter sealant)?

[Topknotrob]

Originally Posted by tkeithlu

A simple soft gasket will do. You've got a smooth surface, a SS plate, and multiple bolts. There is only a few inches of water pressure involved, way less than one PSI. Use Butyl tape or a soft gasket material, and if that does not appear to seal well, some silicone sealant.

Sailmonkey's NO! to 3M 5200 is important. 5200 is for permanent assembly, or situations where you are willing to grind/drill the stuff out if you ever have to, but you hope that you won't. Cured, it is one step short of being epoxy.

General impression: You may be over-thinking a pretty simple situation. Good luck with it.

Thanks for your advice, I think I will steer clear of 5200..

The problem I have is that I won't know if it leaks until I'm in the water, but unfortunately my friend can't afford to be hoisted out again straight away if it does, so I really only have one shot at this and I need to get it right. I pulled a lot of silicone out from old holes, around skin fittings, seacocks etc and personally, I hate the stuff.. I find it just contaminates surrounding areas for painting/sticking etc.

[Sailmonkey]

Originally Posted by Topknotrob

Thanks for this Sailmonkey.



I believe the sheathing may have been a cheap shot attempt at osmosis repair, although I'm not 100% sure. The only reason I was wondering about sanding off the rest of the gelcoat in the area was because it has a few cracks and star crazes and I didn't want to rent the risk of water ingress to the original resin and mat.



Ok, I think 5200 was a bad call then! Will it need to be a sealant that sets, or could I use a cheap butyl type (like gutter sealant)?

Anything that flows under pressure will seal those hairline cracks. Even the cheap gutter seal tape will work fine if it’s silicone free. Like you said, put silicone there and it’ll contaminate the rest of the surface.

[Spot]

Originally Posted by Topknotrob

It's a friends boat and unfortunately he doesn't have the funds to do the legs. What started as a minor lift out for basic remedial work has turned into a full blown restoration as we have uncovered some dodgy repairs etc.
Both engines were seized, but I manage to free them with some diesel and a lot of patience! One of the legs had the hose clip on the bellows rusted in two so water has gotten into that drive.. With this in mind, at least one of them will need a total overhaul and my time is taken up on the boat. We did get quotes of around 2k per leg for professional rebuild, but this would eat into the budget for other more important work.

Would 2 temporary plates really be much different to bolting on the outdrive itself in terms of water ingress?

Sounds like a bigger (!) project...The plates should be fine with a good sealant.

Wondering if washers left on the bolts between the hull and plate would allow even tightening without squeezing out all of the sealant ???
Assuming a caulked or conformable sealant versus a more rigid gasket that would be all around the washers for no leaks.

I would make sure the boat is looked after so you're not the guys who sink at anchor/mooring/slip/dock because something (else) leaked.

All the best to you and you buddy on the rebuild / restoration.