Help, Q about switch from flush to recessed seat pedestal mount

[RubyCreekTed]

I have a 19 ft Starcraft aluminum boat with a center console. About a 1978 model. I am replacing a flush mount seat pedestal mount with one that is recessed about 1 3/4 inches. I figured I could just cut a hole about 3 1/2 inches diameter in the floor material and find a void under the floor. But I drilled about 1 1/2 inches in a couple places where I wanted the hole and hit solid wood. It even felt like sonmething harder than wood at 1/1/2 inches. It looks to me like I have 5-6 inches from the top of the floor to the bottom of the hull at the keel.
I am in the center of the boat right above the keel I expect. Can someone tell me exactly what is likely under the floor before I cut the hole. Can I cut the floor hole and the material under the floor (I am guessing a rib or support, not boat terms) without seriously affecting the floor support? I am replacing the pedestal mount so that I can install a different seat/pedestal. Thanks, RUBY CREEK Ted

 

[oops!]

Re: Help, Q about switch from flush to recessed seat pedestal mount

dont know where you are drilling........but it is possibly the gas tank cover......this is generally in the center of the boat more aft. different manufacturers place the tank in different spots.

EZ is a big starcraft tinny guy......he should be right along with the answer

 

[CBGale2]

Re: Help, Q about switch from flush to recessed seat pedestal mount

Hey Ted. Welcome.

Its hard to know exactly what you have there. Generally its the vinyl floor, a sheet of plywood,some floatation and then the hull itself. If there was a seat there before there might be a backer plate. Can you post some pictures that might shed some light on the situation. We'd like to see the boat anyways. Lol

 

[RubyCreekTed]

Re: Help, Q about switch from flush to recessed seat pedestal mount

Thanks OOPS and CBGale2 for the replies. Not much to take pictures yet but I will try some soon. I think this is an 18 ft instead of 19ft. I see no evidence of there ever being an under floor fuel tank. You may be correct with a backer board under the floor. I suppose I will get a 3 1/2 inch hole saw and slowly work my way down and remove wood as I go to see what is under there. Once I get down 1 5/8 to 1 3/4 inches I am deep enough to install the recessed pedestal mount. I dod see CBGale2's project complete with the floor removed and a second 18 ft starcraft in the U.P. (sorry don't remember the members name) with it's floor removed. Neither picture showed any heavy supports under the center of the floor about 3 feet in front of the splash tray. Any more words of advice. Otherwise out comes the hole saw and chisel this weekend. THANKS again.

Ruby Creek Ted.