SI transducer mounting issue

I have posted this on the general Electronics SI forum, but wanted to see if any of the Arkansas guys had any good solutions:

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.

You are on the right track in my opinion. Either get the mounting board from bass pro, or a thick piece of cutting board or something like that. You can remove the screws and use the same holes for mounting the new board with silicon or some kind of water proof sealant on the back, or do as you said, grind a dip for the screw heads in the new board so the board will lay flat. This is what I did on mine and ended up drilling no holes in the boat. The start is the bottom of page 1, then jump over to page 3 to see the finish.

http://www.crappie.com/crappie/boat-...igging-thread/

RCC, Thanks for the suggestions. I checked your thread on how you mounted the transducer. On my High Def side imaging TD, the instructions say to mount it at least 15 inches to the starboard side of the centerline of the boat bottom to avoid "prop wash" interference. Have you had any issues with that since yours is mounted close to the motor? What size engine are you running? I have a 115 HP , but I realize most of your actual side imaging takes place below 6 mph, so maybe horsepower is not an issue..... by the way, where did you find a thick cutting board. The only ones I have been able to find are only about 3/8ths of an inch thick. The "store bought" ones are an inch thick, so I figured for $20 bucks, I'd stop burning gas looking for a cutting board and just order one from Bass Pro !!

I get prop wash or something in the water column when I am on my trolling motor. I have no issues at all with the outboard. It is a 70hp. If the regular mounting board is $20 and an inch thick, you will be money and time ahead to go that route. When I am looking for fish, I usually run 4 to 6 mph with no issues except lack of fish. You did a good thing by getting the hd transducer. It is much better even on the 798 and on the 899, I believe that allows you to have 800khz scanning.

JB Weld sticks on my rivet holes real good......until i leave the Conway boat trails !