Old Grumman Renegrade.

I've had an '87 Grumman 16' bass boat for about 5 years or so and use it several times a week. It has a Merc Classic 50 on the back. My problem is it shakes with any chop on the water. The console and the whole floor shakes. I can plane at a slower speed to smooth it out but wonder if I can inject Great Stuff under the floor to keep the shaking down. The hull is the shape of a Tracker.