I am happy to address this topic, since, after some 43 years, I removed my trim tabs last year.
My Dad had Trimatic tabs installed on delivery. These were electric, with the motors inboard, a rubber collar at the stern, amd worm gears operating them. Today we know that neither electrics nor worm gears work in a marine environment.
Sets two and three were Bennets. Hydraulic, resevoir behind my bunk in the master. #2 had a single ram each, #3 was installed when I repowered in 1993 with new engines, going from 350 hp to 550. These had two rams each and were longer and wider than set #1, but retained the original resevoir and pump system. On trials, I could force the bow down, but the strain on the hull would be considerable, so I never ran this way. Fanfare has a slight port list despite my loading everything heavy to stbd. I tried to correct this with just some port down trim and it seemed to work, but mostly she seems to correct herself once we start to move, and all is gone by the time we get on plane. Before last spring we never travelled at hull speed unless there were wake restrictions, so never noticed a problem. I'm so used to our list I probably wouldn't notice anyway. But maybe slow speed would be a reason to keep them.
I removed mine for three reasons. I don't have a swim platform, so my tabs were exposed on the stern. Now, I usually dock bow in so people on the dock can't see me drinking in my favorite chair on the afterdeck. Sometimes, however, I have to back in. I do all of my running from the flybridge, and with my 11 ft Whaler behind me my visability to the back is poor. I frequently ran my tabs into the dock pilings, bending the edges. This didn't seem to affect anything, but it was unsightly, and I hate having people see my mistakes.
The second reason was the last set of tabs had a "safety" device consisting of a T-shaped plastic release device, sort of like an outboard's shear pin. Each ram had one of these, so a total of four in all. These just kept breaking, either from hitting the pilings, or, more often, from breaking seas aft. They were still fastened to the hull at their hinge, but when I slowed or stopped they would drop down from their own weight and jam the rudder(s). This was a giant surprise the first time or two! Once I knew of this problem I could give a quick jolt of forward on that side (usually only one would be broken at a time) and the prop wash would move it out of the way. This sure could disrupt a landing! And while having bent tabs looked pretty bad, having a line over the stern holding the tabs up and out of the rudders was worse.
The last reason I removed them was that they really didn't help much. With my extra power I can vary my bow attitude using throttle alone. More power equals bow higher. The tabs really only pushed the bow down. I need a higher bow for larger seas, but at some point this starts to beat the boat up too much. And, while I could try to blame the Admiral, I really try not to be caught out in these seas. At cruise speed our running angle is just fine. and so mostly I never used them.
So I took them off last year to try it. So far I am not inclined to replace them.
