Fibreglass on bow rider strong enough to mount trolling motor?

[kegman]

Hey folks,


I have a 16 ft Scorpion bow rider ski boat. I want to add a Minn Kota Terrova 80lb to the bow. I have access underneath and a flat spot to mount a quick-release (MKA-17) bracket and would mount the trolling motor on an angle about 45 degrees left of center towards the edge. I plan to use the PVC method as posted in this thread to 'level' the bracket with the flat spot in the center: http://forums.iboats.com/showthread.php?t=234469

My question is this:

I've felt around the underside of the bow where I plan to mount the quick release bracket. I expected some plywood or something, but there's nothing but fibreglass - and it appears really thin. I can stand on the spot no problems, but can it withstand 80 lb thrust? I fear the shearing forces would tear the fibreglass / gelcoat etc.


Thank you!


Kegman.

 

[mmccoy555]

Re: Fibreglass on bow rider strong enough to mount trolling motor?

It may hold and may not. I would put atleast a piece of wood underneath if not a metal plate or big washers just to be safe.

 

[arks]

Re: Fibreglass on bow rider strong enough to mount trolling motor?

I agree- you need to add a good backer below the fiberglass. It should be as large as possible to distribute the stress.

 

[Fl_Richard]

Re: Fibreglass on bow rider strong enough to mount trolling motor?

Backer board!

 

[kegman]

Re: Fibreglass on bow rider strong enough to mount trolling motor?

Thanks guys. I was thinking of making it as form-fitting as possible underneath so that it would fit as snugly as possible under that triangular area in the bow. This would distribute the stress to more area of the bow... i.e. a triaguloid shape plus a cutout to accommodate the bow light.

You guys think plywood would do or would I need something 'beefier'?

 

[raekmike]

Re: Fibreglass on bow rider strong enough to mount trolling motor?

keg,
with the 2 different levels it looks like you have underneath you might need 2 seperate backers. 1 for each level. ie one for each 2 bolts that go through. backer material I would recommend would be trex decking or another brand similar. It does not rot shrink hold water or do anything weird. Just make sure you use good size washers top and bottom with whatever backer you use. You can get a 2x6 piece of decking for about $20.

Good Luck..

 

[kegman]

Re: Fibreglass on bow rider strong enough to mount trolling motor?

Thanks Raekmike,


Gonna go over to Bass Pro today to pick up the Terrova. The second level is actually curved (a little hard to see in the photo). I guess I can use washers + rubber washers to fill in any gaps on the underside. On the top side I would use bevelled washers sandwiched between rubber washers to make up the difference in level between the flat center part and the curved part.

Are all bowrider's like this (i.e. just fibreglass)? Or do most have some kind of backing built into the bow area?

Thanks to all!


Cadman.

 

[raekmike]

Re: Fibreglass on bow rider strong enough to mount trolling motor?

yea,
pretty much all the same. yer plan sounds good..show some pics when yer all done.....Good Luck..

 

[kegman]

Re: Fibreglass on bow rider strong enough to mount trolling motor?

Ok. So I finally have some time to trek up north to the cottage and do some drilling into my bow this weekend. Here are more detailed plans...

Option 1: Install the Minn Kota MKA-21 "puck" and position such that the two rear bolts are on the flat part of my bow and the front bolts are on the curved part of my bow. I plan two levels of backing one on the flat part and overlapping below that a larger wood piece that goes right to the edge of the boat for side to side stability.

Advantage - less strain on the rear bolts and flat part of the bow.

Disadvantage - I have to drill into the curved part of the fiberglass and shim them up - the backing won't be flush with the fiberglass underneath because of the curvature, which might lead to uneven pressure on the glass.



Option 2: Install the "puck" entirely on the flat part of the bow. This will mean drilling an additional 6 holes to offset the mount and putting the mounting base on the puck "backwards" to essentially extend and cantilever the motor out so I can clear the edge of the bow. Not sure if the locking pin will clear the rail.

Advantage - Puck will be completely flush with flat part of bow and backing underneath. Puck will look better when engine is not attached.

Disadvantage - additional strain due to cantilever, gotta drill into the other part of the mount to offset the motor forwards. - cantiliver will put more strain on center part of the bow, but the backing will hold up better because it's flat for all four screws. If the pin doesn't clear the rail, may not be feasible.


Thoughts and recommendation on both options before I start drilling?

 

[raekmike]

Re: Fibreglass on bow rider strong enough to mount trolling motor?

Keg,
either should work just fine i'm sure. I only used large washers top and bottom along with rubber washers to absorb some shock with no backer plate. I also used pvc pipe cut to height to acount for the step down on my bow. Click on my name and visit my homepage. I think page 2 has the pics of how i did mine. been working great for 3 years now. no issues whatsoever. Good Luck.

 

[kegman]

Re: Fibreglass on bow rider strong enough to mount trolling motor?

Here are the results of my installation. I decided to get the PowerDrive 70 Lb instead of the Terrova because the Terrova would have been a bit on the 'wide' side and would have interfered with the rail and the light. I wish they sold the RipTide version of the quick release up here in Canada.. would have matched the boat better - I'll pick one up the next time I'm in the states!

I used the 2 1/2 rubber washers on the top left side and 2 rubber washers that came with the motor to shim the mount, I cut them so they created a bevel to accomodate the curved surface - probably need to replace one of the washers with something a bit more solid as there is a bit of give on the right-back corner of the mounting plate when I go hard right.

I also should have shimmed the front part of the puck higher as I didn't account for the weight of me, and the two batteries in the bow.... so the motor is not quite vertical when I'm standing on the bow - but it still works.

I used two pieces of pressure treated wood as backing, one parallel the left rub strip, and a block on the flat spot at the center part.

Glad I got the 70 lb thrust - I don't think i would have been satisfied with the 55 lb version. Can't wait for the iPilot this fall!

Thanks for the help everyone!

 

[raekmike]

Re: Fibreglass on bow rider strong enough to mount trolling motor?

Looks great man! Well DONE!