When you initially hit the throttle the boat
rises and gets on plane then once top speed is reached the nose dives and
the boat looses plane and starts plowing the water

Jason... You are either angling the engine is the wrong direction, or your boat
has developed a hook in its hull.

Joe (30+ Years With OMC)

once top speed is reached the nose dives and
the boat looses plane and starts plowing the water. I have the motor
angled
as far as possible on the mount bracket to lift the front end up but it
still does not get the boat on plane at top speed.

When the trim is set out to the max, is the foot of the motor angled out
past the perpendicular to the line of travel? Does the thrust from the prop
rise to the surface at speed? Maybe you have a highly angled transom, and
the motor needs mount-wedges(shims) to get the desired trim angle.

On 09 Jul 2003 14:20:58 GMT, (ReevesJ32) wrote:

When you initially hit the throttle the boat
rises and gets on plane then once top speed is reached the nose dives and
the boat looses plane and starts plowing the water

Jason... You are either angling the engine is the wrong direction, or your boat
has developed a hook in its hull.

Joe (30+ Years With OMC)

Joe, could it be related to the "short shaft"? If the shaft is too
short for his transom, he'll aspirate the prop as the boat settles
down. The fins he added would likely compound the problem when they
lifted the stern. Just curious.
BTW- thanks for MANY helpful and informative posts.
noah

Courtesy of Lee Yeaton,
See the boats of rec.boats
www.TheBayGuide.com/rec.boats

Sounds like a hook in the hull to me. A boat like this can be downright
dangerous at times.

Is the boat stored on a trailer?

Rob
*
*
*

"JG" wrote in message
.. .
I have a 1968 14ft fiberglass Thundercraft Sprint runabout which is
outfitted with a '68 Merc 35hp shortshaft outboard & a new 3 blade 13p
prop.

I had put stabilizer fins on the motor to help it plane and it actually
slowed the boat down & made things worse. After removing them I regained
some speed but the weirdest thing happens (hence the reason why I tried
the
stabilizer fins to begin with). When you initially hit the throttle the
boat
rises and gets on plane then once top speed is reached the nose dives and
the boat looses plane and starts plowing the water. I have the motor
angled
as far as possible on the mount bracket to lift the front end up but it
still does not get the boat on plane at top speed. Perhaps I am missing
something here? Maybe this has something to do with why the stabilizer
fins
would not work with my setup?
Any help would be appreciated.

Please remove the fifty-five from my address if responding via email.
Thanks!
Jason.

On Wed, 9 Jul 2003 08:25:28 -0400, "JG"
wrote:

I have a 1968 14ft fiberglass Thundercraft Sprint runabout which is
outfitted with a '68 Merc 35hp shortshaft outboard & a new 3 blade 13p prop.

I had put stabilizer fins on the motor to help it plane and it actually
slowed the boat down & made things worse. After removing them I regained
some speed but the weirdest thing happens (hence the reason why I tried the
stabilizer fins to begin with). When you initially hit the throttle the boat
rises and gets on plane then once top speed is reached the nose dives and
the boat looses plane and starts plowing the water. I have the motor angled
as far as possible on the mount bracket to lift the front end up but it
still does not get the boat on plane at top speed. Perhaps I am missing
something here? Maybe this has something to do with why the stabilizer fins
would not work with my setup?
Any help would be appreciated.

Please remove the fifty-five from my address if responding via email.
Thanks!
Jason.


JG- where is the anti-cavitation plate on the engine, compared to the
bottom of the transom. ...is the "flat plate" above the prop higher
or lower than the bottom of the boat?

The short shaft may be your problem.
noah

Courtesy of Lee Yeaton,
See the boats of rec.boats
www.TheBayGuide.com/rec.boats