Bow TM mount on aluminum boat?

[MCHammer40]

Before I go wild drilling holes I want to bounce this off you folks.

I picked up a Minn Kota PD55 for my 17ft Express aluminum boat. Looking at the mounting instructions I need to secure the bolts from the underside - which seems logical, however the aluminum welded front platform and flanges are sealed preventing me from getting underneath. There is a "glove box" that I removed but I still can't reach that far even with special tools.

It looks like the old TM was mounted using something like threaded drywall anchors into which the bolts are screwed - but assume they are specially designed for marine use? I was looking in my local Home Depot and found heavy duty drywall toggle bolts, and another type that cinch up behind the wall as you screw through. I found them in 1/4" bolt size so they seem heavy duty enough to keep the TM in place and they are zinc coated but they are designed for drywall.

Is there a better way to do this? Or is there a special anchoring device that I should use on an aluminum boat?

[TopDog]

I have read that people use either rivnuts or isolator bolts when they cant get underneath.  

Look at isolator bolts at Basspro. Again, I have only read this so I do not speak from experience.

Good luck!

[Wayne P.]

I have no suggestion for your problem, but don't use toggle bolts. The hole you have to make to get the toggle through for a 1/4" bolt is way too big for a snug fit for a trolling motor application. You would just break the toggle apart in a short period of time with retightening trying to prevent movement.

If nobody comes up with a secure method, contact the boat company for their solution.

[Catt]

I can save you a whole lot of trouble because I've tried it every way possible and have found the only secure way is to have a 3/16 aluminum plate welded in place and then attach the motor with ¼ bolts, washers & lock nuts. The picture is not to clear because it was taken at the lake to show the interior layout; the plate goes down & the bends again like a Z & is welded to the deck