Motor board
- Thread starter Andrew C
- Start date
A lot of ways you can go. Out of curiosity what was the old one made from? Do you plan to glass with epoxy? What options do you have in your area? Maybe not a fit for your needs but two layers of 3/4" plywood epoxied together and then cut to shape, smoothed and rounded, and then glassed with epoxy has served me well on several boats. Or do you want to stick with dimensional wood for historical reasons?
Eric
Eric
Steve Sanford
Well-known member
Good morning, Andrew~
I have replaced a dozen or so motor boards on a variety of vessels. I have always used treated 2x10s - which are typically Southern Yellow Pine. I have used old stock that was bone dry. I coat it with 3 coats of epoxy, then 2 or 3 coats of duckboat paint. A new piece of untreated Douglasfir or other framing lumber would suffice - especially if you cut between any larger knots.
View attachment Spirit of Brentwood Motorboard - aft.jpg
I usually add "standoffs" so there is less bearing surface 'tween the board and the hull - so less place to trap moisture. This
View attachment sm MB 03.JPG
The rounded edges help keep the epoxy and paint intact. The rounded cutout on the bottom provides 1) space for drain plug in the transom and 2) serves as a lifting handle.
I shallow-bore 2 "sockets" for the specific motor that will be used. Note, though, that I came across - for the first time this Fall - an outboard for which the 1.5 inch thickness of the x10 was too thin. The screw pads would not tighten fully. (We added a piece of half-inch plywood on theaft side of the board as a retro-fit).
In any event, I bed the bearings surfaces and the bolt holes with a slathering of 3M 5200. I use 4 s/s carriage bolts of 5/16" or 3/8" diameter. They are backed up inside with s/s fender washers - and a 1/2-inch plywood backer board f it's a 'glass hull.
Here's the backer board. The "bumper" protects the gas tank from chafing against the hardware. Note that I've left a spot for a drain plug, too.
View attachment sm 01 SSB Motor Board - backing plate.JPG
Here it is installed on a South Bay Duckboat. The heavy eye-bolt is for a safety line (cable or chain) from the outboard.
View attachment Motor Board y - installed fwd.jpg
Hope this helps,
SJS
I have replaced a dozen or so motor boards on a variety of vessels. I have always used treated 2x10s - which are typically Southern Yellow Pine. I have used old stock that was bone dry. I coat it with 3 coats of epoxy, then 2 or 3 coats of duckboat paint. A new piece of untreated Douglasfir or other framing lumber would suffice - especially if you cut between any larger knots.
View attachment Spirit of Brentwood Motorboard - aft.jpg
I usually add "standoffs" so there is less bearing surface 'tween the board and the hull - so less place to trap moisture. This
View attachment sm MB 03.JPG
The rounded edges help keep the epoxy and paint intact. The rounded cutout on the bottom provides 1) space for drain plug in the transom and 2) serves as a lifting handle.
I shallow-bore 2 "sockets" for the specific motor that will be used. Note, though, that I came across - for the first time this Fall - an outboard for which the 1.5 inch thickness of the x10 was too thin. The screw pads would not tighten fully. (We added a piece of half-inch plywood on theaft side of the board as a retro-fit).
In any event, I bed the bearings surfaces and the bolt holes with a slathering of 3M 5200. I use 4 s/s carriage bolts of 5/16" or 3/8" diameter. They are backed up inside with s/s fender washers - and a 1/2-inch plywood backer board f it's a 'glass hull.
Here's the backer board. The "bumper" protects the gas tank from chafing against the hardware. Note that I've left a spot for a drain plug, too.
View attachment sm 01 SSB Motor Board - backing plate.JPG
Here it is installed on a South Bay Duckboat. The heavy eye-bolt is for a safety line (cable or chain) from the outboard.
View attachment Motor Board y - installed fwd.jpg
Hope this helps,
SJS