Josh Assing wrote:
So, a buddy and I were talking -- he said I wasted my money on trim tabs. I
said I did not.

The conversation revolved around the use of whale tails (foils on the
cavitation plate).

I said that they could help; but would add stress to the outdrive, and if
something that simple really helped, manufactures would make their cavitation
plates larger.

What's the general opinion on them?

Interesting question. I researched this when I bought my 14'
Princecraft with a 25 Johnson a couple of years ago.

There are two types that I'm aware of - Doelfin and Permatrim. Doelfin's
work like an airplane wing providing lift to the stern under power
forcing the bow down. Doelfins basically work with the water without
impeding the water flow.

The Permatrim devices work a little differently in that they work with
the water off the prop creating lift by retaining the water that spins
off the end of the prop and creating stern lift pressure that way.

I tested boats with both types and I can't really see where they make
much of a difference on boats with electric trim control. On small
boats, like my Princecraft, there is a difference because the running
trim angle is fixed and allows for quick bow lift and a pretty solid
running angle. Both types exhibit an odd tendency to dig in a sharp
turn which can bury the stern and on the boats I tested, prop cavitation
in turns where I wouldn't have expected a non-equipped prop to cavitate.

In my opinion, for boats with fixed trim, I can see where they would be
advantageous. With electric trim, not so much.

As to stress on the outdrive - it's negligible and not something that I
would worry about.

Boat trim is all about the proper application of power - meaning that
prop sizing, fixed trim angle and engine leg size are the real important
criteria. Can you adjust for any of these if they aren't correct with
one of these devices? I would say yes, but I wouldn't be the first one
on the block to buy one if I was having trim angle problems on take off.

I'd try something else first.