On Wed, 02 Apr 1997 13:46:36 -0500, Critterdoc
>I agree that fins will weaken/stress the anti-vent plate, but don't
>think it accurate to state with certainty that they "will eventually
>break the plate". In some boats they can be helpful, in some boats they
>can actually degrade performance. I would not agree that they are
>garbage, but do feel that they are a less expensive and less functional
>alternative to real trim tabs...which can be a *hugh asset* in many many
>I have no doubt that fins have contributed to failure of the
>anti-ventilation plate on some engines, but suspect that such failure is
>not really common. However, if its my boat, 1/Ks is too much.
>My only "support" of the fact that failures can occur is to share my
>dealers experience of having seen a number of plates fail over a period
>of years, and word-of-mouth opinion of several *knowledgable* boat
>operators that state their reluctance/refusal to use them because they
>know of cases wherein fins have contributed to plate failure.
as for me i also work in the industry as a mobile tech
so i get to see a lot of difernt yards and boats
my experiance is that these fins when time and corrosion
take there toll usualy snap the plate .
also where i see this the most is on the yamahas first and then the
johnsons , whith the johnsons i usualy see a lot of degradation in the
lower case ,but the yamahas for some reason i don't see this, i think
they may just be weaker thinner in general in the ant- cavition plate
Also common sense stands to reason a little here, all these fins do
is lift the transom of the boat by defelting the water downward .
think about the force generated by this technique that is all directed
at the anti cavition plate.[what are we talking here a peice of cast
alluminum 1/4 inch thick if your lucky b-4 corosiion. ]
BTW my experience is in sal***er [atlantic ocean]where the corosion
pocess is a lot faster
I should have said this in the begining sorry all !!!