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View Full Version : Platform Backing Plates Revisited


sethro
03-04-2008, 11:20 AM
I've searched the threads regarding this topic, and I thought I would bring it back to life in another thread. My main question is, has anyone else done the West System Epoxy filler method detailed by Sporty here (http://www.tmcowners.com/teamtalk/showthread.php?t=5012&highlight=backing+plate)?

I'm going to reinforce my platform on my 85, but haven't decided if I want to cut out the floor and use backing plates or try the filler method. I don't think I'm in danger of the platfrom coming off, as it looks like a repair was done in the past...though I'm thinking it was probably just larger lag bolts and nothing else. But I do weigh 240lbs and want the piece of mind that it's fixed correctly.

Furthermore, I would like to put some kind of hard rubber gasket between the bracket and the hull, basically just to clean the look up a bit...much like a light switch cover to hide the repair area as the transom is not showroom perfect behind the mounting plates anymore.

I'm also considering removable (quick release style) brackets but not sure if I'll go that route. Any thoughts???

BrandonKTM
03-04-2008, 12:37 PM
I looked over the backing plate thread. I have an 84 and we did a much simpler fix. Remove gas tank, remove brackets, drill existing holes all the way thru, replace lag screws with stainless bolts, lock nuts and fender washers on inside. Put waterproof caulking in holes before pushingbolts thru. No problem in 10 years. I would not recommend putting any gasket type material between bracket and hull. Movement on the platform will compress material, in,out,in,out forever. This will allow for leverage and hull will be damaged.

sethro
03-04-2008, 12:56 PM
Brandon,

Are you saying you didn't have to cut the floor out to access the inside where the lag screws enter? Everything I've read says inside of the transom can only be accessed by cutting out the floor...haven't had my tank out yet to confirm this on my boat.

If I can access the area without cutting the floor, options are much easier. One guy I remember was able to acess the top two holes for the platform and just reinforced those.

Thanks.

Killerack
03-04-2008, 01:06 PM
Sethro,
I had an 85 and did pretty much the same as Brandon except I did make 2) 1/4" thick backing plates and installed. Either way you go it will be better than factory. Once you get the tank out you'll find it's straight forward.

sethro
03-04-2008, 06:08 PM
Killerack,

Same question to you...are you saying you didn't have to cut out your floor to access the area on the inside of the transom?

That would be great, but I'm almost thinking this is one of those "some boats you do, some you don't" deals. Hopefully I'll get the tank pulled this Friday and know for sure.

BrianM
03-04-2008, 06:20 PM
If you want a bit of a gasket or backing plate to go between the bracket and the hull how about using a thin piece of lexan? The material will not compress and it should work just fine if you are trying to cover those couple of spider cracks near the bolt holes.

I think I would use the epoxy method first and see if that works to your satisfaction.



For epoxy filler use:
Drill the holes about 1/8” oversize (but I m skeptical of the drilling after I saw the spalled areas on my outside finish from the bracket removal).

Use an epoxy / resin hardener in a manner of a high slump consistency (thin consistency) and coat the inside of the screw hole(s) with this consistency of mixture (to seal the inside diameter area of the hole(s)). Then before that begins to cure, add additional 404 filler (apparently their product reference number) to reduce the slump consistency (thicken the mixture) and fill the hole(s) with this thicker add mixture consistency, as full as possible. Spray the lag screws with Pam cooking spray which will act as a barrier for the filler mixture in which not to adhere to the screws. This will allow the removal of the screws in a future step. In addition brush on the 404 mixture onto the screw threads, insert the screw into the holes and allow this to cure at least 12 hours. After the proper curing time, the screws will be able to be removed, leaving an epoxy-molded insert for reattachment of the platform to the boat. Upon removal of the embedded screws, if the screws exhibit a cracking sound or chip a bit of epoxy out while removing; simply brush on a bit more epoxy filler material upon entry placement of the screws when attaching the platform. This will fill in any cracked areas or chipped places inside of the epoxy-molded insert. Done deal.

Needless to say, use a silicone sealer as well on each bolted connection point to seal out any water.

Had I have seriously considered my options with the hind sight I have now (and foresight of completion) of the surgical procedure on my hull, I’d likely have tried this epoxy filler method first.



.

Jim@BAWS
03-04-2008, 06:51 PM
I looked over the backing plate thread. I have an 84 and we did a much simpler fix. Remove gas tank, remove brackets, drill existing holes all the way thru, replace lag screws with stainless bolts, lock nuts and fender washers on inside. Put waterproof caulking in holes before pushingbolts thru. No problem in 10 years. I would not recommend putting any gasket type material between bracket and hull. Movement on the platform will compress material, in,out,in,out forever. This will allow for leverage and hull will be damaged.


This is what we have done and it works perfect. My suggestion is
to get NEW removable platform brakets when you do it
That way you can always remove the platfrom

When the tank comes out everything is exposed in the stern
and easy to get to

Not a tough job at all to do

Jim@BAWS

cbryan70
03-04-2008, 07:22 PM
i have a 78 im giong to be doing the same thing to. I was thinking drilling out the holes for the new brackets and putting a 1/4 inch backing plate in there as well. Think that this is over kill? Also i will have 4 brackets as that is the way the platform is. Should i throw all 4 on or just go with 2? I figure the more brackets the better in an older boat but i could be completly wrong. sorry forthe thread jack

drylandfish
03-04-2008, 07:47 PM
Sethro, you will have to cut thru the floor under the gas tank just like Sporty and dichdoc have done in their threads. I just took the tank out of my '84 this past weekend and there is no other way to get a backing plate on for thru bolts. Good luck with whatever you decide to do.

sethro
03-04-2008, 08:09 PM
I'm definitely not going to be certain in my head about cutting out the floor till I take out MY tank. :) My friend's 84 is accessible, but it is obvious from previous threads and drylandfish's post that some are not.

Cbryan, four brackets would definitely be overkill in my opinion...but the backing plate seems like a good idea.

BrianM, lexan would probably work. I'm envisioning a "cafeteria tray" shape but much more sublte edges.

Cloaked
03-04-2008, 08:43 PM
I'm definitely not going to be certain in my head about cutting out the floor till I take out MY tank. :) My friend's 84 is accessible, but it is obvious from previous threads and drylandfish's post that some are not.

Cbryan, four brackets would definitely be overkill in my opinion...but the backing plate seems like a good idea.

BrianM, lexan would probably work. I'm envisioning a "cafeteria tray" shape but much more sublte edges.By not going under the floor, one would be raising the platform up about 2 - 3 inches (to just drill through and bolt above the floor), only to interfere with the transom eyes. It doesn't measure up (by looking at Sporty's pics). The 84 - 85 models are all the same. Going under the floor is the only way to set the platform properly at the water line.

Don't worry about removing the fuel cell. Just unbolt it and slide it forward. Makes the project much easier with less work.

Been there.

cbryan70
03-04-2008, 10:51 PM
WEll looked at it all today and i wont need to cut the floor everything will be good to go once the gas tank is removed

drylandfish
03-04-2008, 11:47 PM
Cloaked it right about being close to the transom eyes. When you remove the tank you'll see where the transom eyes bolt through and their backing plate. Measure from the botton transom eye nut to the floor and then go to the outside of the boat and measure again and see where the floor is. If you are gonna bolt the platform up in the existing position I can't see how you would avoid going under the floor. I know it's a lot of work and most people would like to avoid it, but personally I don't see any other way. I will go ahead and admit that I've been wrong before though.

robisjo
03-05-2008, 12:48 AM
This is what we have done and it works perfect. My suggestion is
to get NEW removable platform brakets when you do it
That way you can always remove the platfrom

When the tank comes out everything is exposed in the stern
and easy to get to

Not a tough job at all to do

Jim@BAWS

When I did my 85, I got the removeable platform brakets, they worked great. I installed some metal backing plates and never had anymore problems with it. I did have to cut out a portion of the floor and filled the exisiting holes with resin, a couple of the wholes were the size of a dime.

Good Luck

BrandonKTM
03-05-2008, 10:31 AM
Sethro, Sorry for the delay on my reply. No, for my 84 I did not have to cut out the floor at all. Its been a while, but I think we just slid the tank forward enough (ie did not drain it)to reach behind it to get to the bolts to put the washers and locknuts on.As for a backing plate, the disadvantage to that over fender washers is that the fiberglass on the inside is not smooth or flat to match the plate. Then you will get uneven pressure applied to the hull. IMHO its a lot easier with washers, and probably less $ too.

sethro
03-05-2008, 08:49 PM
Hey thanks, I'm now convinced I won't know till I pull the tank. I'd rather not cut out the floor, but I don't think it would be that big of a deal.

sethro
03-12-2008, 02:25 PM
Well, it's official. I've got no access to my platform bolts without cutting out the floor. Furthermore, the attempted fix years prior is going to make it harder I'm afraid. Looks like someone drilled access holes where the floor meets the transom to get some epoxy down to the lags, but I can't tell for sure. I'm convinced to do this right I must cut out the floor and reinforce with backing plates so it looks like that's what I'll do.

I'll be sure to post some pics along the way.

sethro
03-13-2008, 01:00 AM
Ok, so I cut a section of the floor out tonight only to stumble onto yet another hurdle. The outside stringer (I assume it's a stringer) is directly in line with where I need access for the bolts. Now, this is hollow and there was a gap between it and the floor. I reread Sporty's post that I linked to in the first post of this thread and he mentions..."you’ll see the transom area from the inside (after the foam and a section of the baffle was removed) where the brackets attach to the transom (on the outside)"... so I can only assume he removed the section of stringer (baffle).

So, my question would be can I remove this and not worry about replacing? Doesn't seem possible I could remove a section of the stringer system without issues, but I can't imagine putting it back in after cutting it out would be any good either. There is no foam in that area and using a mirror I can see where the foam starts...referencing the cutout photo of the composite construction indicates there is foam inside and between the stringers...no foam near the transom on my boat.

Harold, if you are reading this thread any chance your contact from MasterCraft would have an opinion on whether I can remove enough to get a backing plate on the transom? You can also see where a previous owner drilled some holes so epoxy could be injected down in there. If I can't remove the section of stringer, I'm going to do the West System Epoxy method...which probably would be fine anyway I guess.

Here are some photos:
32377

32378

sethro
04-28-2008, 04:47 PM
Well it's been difficult finding time to finish off my platform backing plate project, but it's finally done. I decided to have my friend that welds aluminum cut off the old mounting plates for the platform brackets and weld on new, larger ones. The bottom holes in my transom were not bad, so I used the West System Epoxy method detailed by Sporty in the link in my first post of this thread. I'm quite impressed with the epoxy molded inserts and their holding power.

The top holes were raised about 1" and offset enough to clear the bracket. I used the old mounting plate from the platform bracket that was cut off for the backing plate inside the transom. Although the top holes were raised, the platform remains at the same level on the transom as before. The platform is now VERY solid and actually exceeded my expectations.

Here are a few pics:
34195

34196

34197

BrianM
04-28-2008, 06:11 PM
Looks good.. You can barely tell that you modified the bracket.

TMCNo1
04-28-2008, 08:34 PM
Ok, so I cut a section of the floor out tonight only to stumble onto yet another hurdle. The outside stringer (I assume it's a stringer) is directly in line with where I need access for the bolts. Now, this is hollow and there was a gap between it and the floor. I reread Sporty's post that I linked to in the first post of this thread and he mentions..."you’ll see the transom area from the inside (after the foam and a section of the baffle was removed) where the brackets attach to the transom (on the outside)"... so I can only assume he removed the section of stringer (baffle).

So, my question would be can I remove this and not worry about replacing? Doesn't seem possible I could remove a section of the stringer system without issues, but I can't imagine putting it back in after cutting it out would be any good either. There is no foam in that area and using a mirror I can see where the foam starts...referencing the cutout photo of the composite construction indicates there is foam inside and between the stringers...no foam near the transom on my boat.

Harold, if you are reading this thread any chance your contact from MasterCraft would have an opinion on whether I can remove enough to get a backing plate on the transom? You can also see where a previous owner drilled some holes so epoxy could be injected down in there. If I can't remove the section of stringer, I'm going to do the West System Epoxy method...which probably would be fine anyway I guess.

Here are some photos:
32377

32378

That should not be the stringer! The stringer runs along the edge of the bilge that the motor mounts bolt to and drops down to the hull and hull liner. That is one of the corragated fiberglass runners outside the stringers that is just part of the floor and floatation system and it won't hurt to cut it out, just as long as you replace it, foam it up and seal it all back. PM Ski King to post a picture of the mid '80's cutaway drawing he has from a brochure and you'll see what I'm talking about.

sethro
04-28-2008, 09:59 PM
I have that brochure as well, and my thoughts were that it wasn't the main stringer...just part of the composite stringer system. I did contact MC about cutting that out and it would not have been a problem as long as I was able to secure it back in place. I did have to inject foam on the starboard side where for some reason at the factory the last 18" to the transom didn't receive the foam. The outside runner in the picture was even hollow for that last 18" or so...somebody goofed during the build.

Anyway, the epoxy molded insert for the lags on the bottom works quite well, and I'm pleased with the rigidity of the final product.

defender1009
04-28-2008, 10:01 PM
Man, that sucks you had to cut the floor for nothing.

sethro
04-28-2008, 10:56 PM
Yes, I could have done what I did without removing the floor section and in hindsight that bites...though that part really was pretty easy. But I wouldn't have discovered the lack of foam either. I had still planned on cutting out the "runner" and installing a backing plate on the bottom as well, but after talking with a tech rep from West System Epoxy I was convinced the bottom holes would be fine with the epoxy molded inserts for the lag screws.

When I was watching the movement of the platfrom when I would put pressure on it (prior to fixing it) the top mounts tended to pull away from the transom while the bottom seemed to exert it's forces back towards the transom...which would probably explain why the bottom holes were still ok while the top was quite weak.

LGP
05-22-2013, 04:31 PM
I removed the fuel tank last night and someone had already cut out part of the flooring but had not replaced it! I can still access the two upper bolts and was able to remove them. who ever had worked on this before did not add backing and the bolts were pulling away from the hull.
I read the article you provided and will follow that for the bottom two bolts. Thank you so much for your help on this one... really appreciated!
d

sethro
05-22-2013, 06:53 PM
Glad you have it under control...is the floor piece still around or is it gone? I would be concerned about water getting under the floor if there is nothing there.

The epoxy molded inserts work really well. I jacked up the back of the boat to aid in getting the epoxy in the holes. So well that it would probably be fine for the top bolts too...but backing plates are better yet.

Cloaked
05-22-2013, 07:09 PM
I removed the fuel tank last night and someone had already cut out part of the flooring but had not replaced it! I can still access the two upper bolts and was able to remove them. who ever had worked on this before did not add backing and the bolts were pulling away from the hull.
I read the article you provided and will follow that for the bottom two bolts. Thank you so much for your help on this one... really appreciated!
d
You are speaking to a post that was last entered in 2008

- 5 years ago....... :D

Jethro is still around though.....

.