Hello,
I hope I can get some advice on what to do about my problem. I have an old
15 foot, 70-something Bayliner that I have inherited. (Was that stupid to
take it or what?) Anyway, I recently bought a replacement 50hp motor for
the boat (long story about what happened to the other one) off Craigslist.
The motor is nearly identical to the one that it was replacing, but after
using it a few times I realize that it is about 6 inches shorter than the
old motor.
I was wondering why it wouldn't plane, and sounded as if it was cavitating
and ventilating - it was! It works fine at low speeds, but when I go full
power I get a little push then it slows as the prop sucks air and doesn't
get a good bite of water.

So, after closer examination, fiddling with the trim, and saying bad things
to it....I realize that I'm dealing with a motor that is about 4-6 inches
shorter.

Is there anything I can do to solve this problem short of buying a longer
motor or shortening the transom of the boat? I was thinking of one of those
hydroplane fins like this:
http://www.westmarine.com/webapp/wcs...man/asc/0/grid

but not sure how that would work. As you can see in the photos (links
below), the cavitation plate is above the keel of the boat, although when
running, it's right on the surface of the water.

Side view of engine and mounting:
http://home.comcast.net/~tegwilym/boat/motor-side.jpg

Rear-on view showing cavitation plate location in refrence to the keel -
about ~3 inches above the keel. (arrrghh!)
http://home.comcast.net/~tegwilym/boat/motor-back.jpg


Side view showing location of prop/cavitation plate in relation to the keel:
http://home.comcast.net/~tegwilym/boat/Motor-close.jpg

The mount doesn't seem to have any vertical hight adjustment as far as I can
see. The motor is about a 1965 vintage Mercury 50hp.

Does anyone have advice for a newbie motorboat owner who is learning a lot
in the last few weeks from mistakes??

Any advice - or pointing and laughing - is welcome! :-)

Thanks!


Tom
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