mbowers
Well-Known Member
My SS175HW was mounted thru-hull last time and while it was phenominal at lower speeds, when speeds picked up it was intermittent. That is because on aluminum boats you require a plastic spacer between the transducer and the hull. I'd say that spacer was about 3/8" which really disturbed the water. I am planning to do what BCI mentioned above on point #4. I can't remember where I saw this pic from but it looks pretty slick. BCI with the spacer in place, I was thinking that I'd have the bracket mounted to that it was 2mm below the hull. What are your thoughts there?
For the through hull transducer did you ever try a little trim tab to drop the bow and clean up the water flow? Works for me and everyone else Ive talked to who had the same complaint about higher speed issues. From how your experience went with that boat is it possible it was just a badly done transducer install?

For the transom mount Totalscan Lowrance transducer with Chirp, it is perfectly acceptable to have the transducer out of the water per Lowrance.

I don't really like the idea of transom transducers on plane because there is a lot of complicated water flow there to get a good signal but maybe the tab version is ok. I would most definitely not let any builder make a change to the transom design by adding a tab without checking with the hull designer. That is the most sensitive area of hull design. In my case, the clown that bought the company from the original designer circus built my boat with a pack of monkeys. They mounted the trim tabs a little low so they dragged and the boat would porpoise. The builder blamed the slightly larger gas tank for the porpoise. Since I traded in one of the original hulls which never porpoised, I didn't believe the builder and checked with the original hull designer/builder. He confirmed that if the trim tabs dragged when retracted the hull would porpoise. I moved my trim tabs and the porpoise went away. So be very careful when making any changes to the running surface, especially at the transom.
Cool topics and great to learn from all the contributions .. Will attempt to integrate into my next build.