OK, I got a new 899 ci hd si unit and have done the exchange for the High Def transducer. My issue is that my aluminum boat has 6 holes drilled thru the transom from the current and a previous transducer mounting exactly in the place that I need to mount the new transducer. This prevents me from mounting the new transducer bracket without the current screw heads from being in the way of letting the new bracket from laying flat.I am concerned that if I don't leave the stainless steel screws in the current holes,I will have leaks in the boat. I am considering using the plastic transducer mounting deal from Bass Pro, but it will still have to be drilled or routered to accomodate the existing screw heads so it will lay flat on the transom. I guess I could JB weld the holes, but I am concerned that they would would not hold up over time. I am thinking of routering out a place in the plastic mount to let the current screw heads fit in behind the plastic, then silicon caulking the crap out of it, holding the plastic with a couple of screws and - finally - mounting the new SI transducer to the plastic may be my best bet. There will be a gap of an inch or so from the bottom of the plastic mounting plate to the bottom of the transducer. Will that create a "turbulance" issue?

I could get the current holes welded but there would still be a "hump" on the outside of the transom from the welding which would not allow the plastic mounting plate to lay flat against the transom. I don't think it is possible to reach the area of the holes from the inside of the transom for it to be welded from that side.

Any ideas to help with my concerns would be appreciated..... maybe I'm over thinking it !! Thanks.