Finally got the Doel-fin on the 25 HP Yamaha and while I haven't yet run it through the gamut of tests I intend to, it instantly improved the performance and running attitude of the tender with no ill effects that I've noticed. Not too terribly hard to install although not without a challenge or two. And now removing the zinc on the cavitation plate would require removal of the fins, although it's not a zinc that gets much of a workout as it's out of the water other than when the tender is being run.Doel-Fin will make a huge difference. I have one on my 15 HP Yamaha, made a dramatic difference in how it planes and general stability. Took all the squirreliness out of the dink and it pops on plane. Highly recommend, not hard to install. Wouldn't be without them.
I'm hoping to get the benefit of the collective experience of the group on the benefit of using a whale tail on the cavitation plate of my tenders outboard. The problem I'm trying to cure is an extreme bow up condition when accelerating to a plane. The dinghy is a WM hypalon 3.10 rib with a 9.9 Mercury 4 stroke. The motor is set at the lowest position (bow down) possible. Even with that keeping the bow from pointing at the noon sun requires my arm on the tiller stretched out straight and my ample center gravity as forward as I can reach. Once on plane and the bow comes down things are ok. With two people the boats behavior is more civilized.
Would one of the whale tail devices help in this situation and if so, which of the several brands have you experienced satisfactory results?
Mine really helps my boat plane and stops proposing. I have an 11 ft whaler with 15 hp Honda.The problem with any foil that you attach to the lower unit it, you are now introducing lift via the outboard. This is transferring force to the transom vertically at the engine mounting bolts. For most dinghy's these are just screwed tight and not through bolted.
Ideally, the boat should be planing as a result of lifting forces on the hull. Trim tabs and proper trim through load distribution is the better solution IMHO.