Drilling Transom Bracket Holes...

[holgo123]

Any tips on drilling transom bracket holes through a newly replaced transom on a 1993 Chris Craft Concept BR 217? It has a OMC Cobra 5.0 L V-8 in it. I am worried about keeping the holes squared up as I drill through. The transom is 2" thick where the outdrive passes through the transom. Thanks for any advice...

 

[Mark42]

Re: Drilling Transom Bracket Holes...

I have two suggestions:

1) To drill perpendicular to the transome, take a good piece of 2x4 and drill the size hole you need using a drill press. Then hold the 2x4 against the transom and use it as a guide to keep the bit "square" to the transom. If you need to drill at an angle other than 90*, then set the drill press at the appropriate angle when drilling the guide hole in the 2x4.

2) Transom rot often starts where bracket bolts pass through and the sealer (if any was used) fails and water starts leaking in. To prevent this in the future, drill oversize holes and fill with epoxy. When fully cured, then drill the actual size hole through the epoxy. IE drill a 1" hole, fill with epoxy, then drill the 5/8" hole for the bolts through the 1" epoxy "plug". Now, even if water does get past your bolt hole sealer, it will not get into the wood of your transom.

Best of luck with the boat!

 

[sdunt]

Re: Drilling Transom Bracket Holes...

Another technique is to line the bolt holes like the drain with brass tubing:

Where many transoms fail is all of the bolt and screw holes in them that allow water in and past any epoxy seal.. One Idea I picked up is to use tubing to seal the holes. My appologies to the original poster that I copied this off of:
"go to good ACE/TRUE VALUE hardware or hobby shop that sells K & S tubing..

buy a piece of tubing with an ID size that is two to three sizes bigger than your bolts.. but is still a common drill bit size on the OD..

bore holes thru the transom and install the tube all the way thru the transom, coat the outside of the tube with epoxy before you install the tube, you want to cement it in place and seal it and the wood you just punched a hole in.

As you install the bolts, shoot caulk/silcone in the tube in between the bolt and the tube to water seal 'the hole in the boat'

the tube isolates/seals/protects from water infusion and isolates it from EVER soakin' into the side walls of your new transom. Kind of like making a drain plug hole but for the motor mounts or any other holes in the transom."

 

[ironhorse]

Re: Drilling Transom Bracket Holes...

you can also drill the hole then take a drumel tool and drill out the core then fill with epoxy

 

[rebuilt]

Re: Drilling Transom Bracket Holes...

Seems to me Mark 42 took care the need to get a hole that is squared to the surface. If you don't have access to a drill press, there is another way.
Play with the trailer jack until the transom is true plumb, as checked with a level. A torpedo level would do. Or a 2 footer, or a 4 footer. Once the transom is plumb, put the torpedo level on top of your portable drill, and drill away, keeping the drill level with the bubble. This won't take care of side to side out of square, but I'm betting you can keep that where you need to with a good eye. Good luck. KR