"MikeG" wrote in message
...
I have a 17 ft, older trihul. The more throttle I give the more the bow
stands up.

This is common, to a point. On a typical runabout, especially one that is
stern heavy, opening the throttle immediatly causes the bow to rise. If you
give it enough throttle it eventually "climbs on top" and starts to plane.
At this point the bow comes down and the boat takes on a more level (though
still slightly bow up) attitude.

Many runabouts have a significant drawback (some might consider it to be a
flaw) that the boat is just impossible to handle at medium slow speeds. At
idle they are fine, and once they are on plane they are fine, but there are
speeds where the bow is up so high that the driver can't see and it simply
doesn't handle. Many times this is not a problem, until you want to pull a
kneeboard or similar water toy that requires you to go 12 MPH.

I was reading recently about planing. Would my boat be
considered a displacement boat?

No, definately not.

or is it just set up wrong.

Maybe.


The boat has a Volvo 140 i/o with now trim tab. There are some "trim
plates" on the back.

Should be okay.


Also, am I missing some "trim" thing on my outdrive? Something like this

I really doubt that these would make a significant difference. They can
make a difference on really light boats, or if you need just a tiny bit of
extra help. It sounds like you need more help than what this would offer.

I noticed your response to another person where you said that the outdrive
is in the position nearest to vertical. It would help to get on plane if
you could actually take the outdrive beyond vertical, so that it tucked up
under the boat slightly. You should also make sure that the outdrive is
lowering to this position when you are in the water. It is possible that
the mechanism that lowers the outdrive isn't allowing to go all the way down
to the pin. Having the outdrive in a partially raised position would
certainly cause what you describe.

The next recommendation would be to move more weight to the front. I have
driven boats where I had to get people to move to the bow in order to get
the boat up on plane! Loading your ice chests, anchors, etc. farther
forward might help out a lot.

You may just be suffering from lack of power. 140 Hp should be enough, but
if this "older" engine is a bit tired it just may lack the get up and go to
get up on plane.

Finally, see if there is a manual adjustment on those trim tabs. If you can
get them to deflect down a bit more they may help lift the boat up on plane.

Good luck
Rod