motorboard help/3M 5200 help

Chris S.

Chris S.

Well-known member
In the next few weeks I am gonna be changing ther motorboard on my BBSB. It sits to low. It is 13 3/4 inches and should be at least 15 inches from the bottom of the stern. I had to shim the motor up last year. I could only safely shim the motor up 1 inch so there was still enough motorboard for the clamps to bite on. I want to take off the old board and put a new one on.

Here is a pic of the motorboard I want to take off just the motorboard and leave the little angle pieces attached to the transom. When putting this motorboard on I glued/sealed it with 3M 5200. I did this for attaching the little angle pieces to the transom and for attaching the board to the angle pieces. You can see the white 5200 on both sides of the little angle pieces.

So my question is what is the best way to break the bond of the 5200. I don't care about the old board so I was thinking about a sawsall down the middle and cut away as much as I can without damaging the angle pieces. Then a little chissle and a belt sander to clean up the rest and have a clean surface on the angle pieces to put the new board on. My concern is by using to much force that I will pull the glass off the transom and make this a bigger repair job then it needs to be. Anyone have any experience with breaking the bond of 5200? What is the best way to remove the board like I want to without any extra damage to glass and transom.

After I get the old one off and get a new piece of white oak for the motorboard and get it all lined up with the bolt holes. I was thinking about starting it off at a height 16 1/2 inches and working my way down. Cutting a little off at a time till its at the perfect height. I was told that with a BBSB it is ok to have the motor a little higher then 15 inches because the stern squats a little bit. I have seen some guys have there short shaft motors at 16 inches or higher it just depends on the boat. I know some of you guys know a lot more about motor height and the cavitation plate then I do. Any help I can get or ideas would be great. Thanks for the help.

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Chris, the 5200 is not a glue, it is a bonding sealer. It does not hold things structurally. You should be able to drive the bolts out and then you can simply snap off the motor mount. You can use a sharp chisel to scrape down to the hull. I have found a ROS does a decent job too of removing it from the hull, just keep the sander moving.

When you attach the new one, I would use epoxy to build the structural portions and only use the 5200 to bed the screws. The 5200 is always flexible and should not be used as a glue, but as a seal. Coat your bolts with wax or vaseline if you use them to align and hold everything as you epoxy, then remove them, chase the holes with a drill again, and then use the 5200 to bed the hardware. Dave Clark always advocated for carriage bolts, but I am not a fan when used in wood. I like to be able to tighten bolts in the future when the wood compresses, and it will compress.
 
Ditto what Dave said plus ............I've used just a sharp knife or sharp chisel to break it loose and get it off.
 
Dave,
Because i did use 5200 do you think I shoud remove the whole thing and redo it with epoxy rather then the 5200 that is holding it now. I still have some epoxy left over that I could do the job with epoxy. would wood flour be ok to use to thicken the epoxy and glue it on then through bolt

If you were doing the job how would you do it?
 
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If it were me.... I would try to drive the bolts out first. This might be challenge as you will likely need 2 people....one to be inside the hull, aligning a rod to serve as the punch/drive pin to drive the bolts. THe other guy to man the mallet. I would drive all 4 bolts together rather than one at a time, thinking you will likely seperate the motorboard and wedges from the hull this way before splitting something. Once it is off the hull, and can be properly supported, your success at driving each bolt is better. If you can get the parts seperated, I would clean up all the 5200 and then do as I suggested above. Re-install the new board with thickened epoxy, then bed the hardware with the 5200. By using 5200 on such a high stress component as your "glue" you really are asking the bolts to support all the weight and stress, and you will get compression because you are allowing movement with the 5200.
 
Is wood flour ok to use to thicken the epoxy or would you use cabosil? I have wood flour and epoxy left over but can buy cabosil.
 
Cabosil might be better, but I think the wood flour will work fine for this. If you wre relying on the epoxy as your "fastener" I would suggest the cabosil, but as I assume you will still use the 4 botls, I would use the wood flour. You are just looking for a fixed/rigid connection.
 
Yeah me too. I would love one. I am always up for donations or a field tester haha. Talk to you soon.
 
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Hey rich did you paint that motor yet? That's why I kept missing the birds last year I couldn't stop looking at that shiny motor.
 
Oh awesome I bet the griz worked really well. You still planing on coming down this summer for a boat ride. Also you gonna make it to the get together on july 21st as long as it doesn't get canceled with all the downed trees
 
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