wrote:
On Sun, 11 Apr 2010 18:52:39 -0400, wrote:


wrote in message
...

On Sun, 11 Apr 2010 12:02:30 -0400, wrote:


A pontoon still has a step where the hulls level out a bit higher in
the water than pure displacement. More speed generally raises that up
a little but at a pretty good increase in fuel consumption.
If the motor and boat are well matched it will be up on the step and
leveled out at 3200 - 3400 RPM. Bumping that up to around 4000 RPM
gives you a good cruise speed and a healthy RPM for a 2 stroke engine.
.

I'm just happy to keep my prop deep enough in the water to keep the
cavitation down. When cruising around the Banana or Indian Rivers, any
chop
at all will cause it to cavitate at 3,000-3,800 RPMs and if almost can't
run
at over 4k at all.
It's a long shaft 50 Force and the cavitation plate is just under the
surface. Should I move the motor lower? Probably involve a either one of
those brackets used to move an OB out from the transome (name escapes me
this morning) or chopping the crap out of my outboard mount, something I'd
really like to avoid.

That sounds high. The cavitation plate should be below water going at
any speed. If it is barely underwater at rest it will be lifting out.
Where is it in relation to the skid on the motor bracket?That was what
I used as a guide on mine. It sits about an inch below the bottom of a
straight edge, laid on the skid plate.

Sorry about the bad resolution, it is the only picture I could find
http://gfretwell.com/ftp/engine%20mounting.jpg

I can see it fine. Also, I can see where the prop is in relation to the
pontoons.
Thanks and I'll compare it to mine. Or compare mine to yours. Boats that is.
Ha!


Bear in mind this is 4" above the stock location and the prop does
blow out on a hard turn at speed. My goal was shallow running

Looks like you could use a jack plate, too.

wrote:
On Mon, 12 Apr 2010 20:01:44 -0400,
wrote:


Bear in mind this is 4" above the stock location and the prop does
blow out on a hard turn at speed. My goal was shallow running


Looks like you could use a jack plate, too.


Why? Sounds like a lot of extra complexity for a dubious gain.

For running in shallow water? That is his goal.

wrote in message
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On Mon, 12 Apr 2010 09:19:48 -0400, "mmc" wrote:

Bear in mind this is 4" above the stock location and the prop does
blow out on a hard turn at speed. My goal was shallow running
Thanks, I'm just trying to run down what my problem is and this will help
I
think. How deep was your cav plate in the stock position? We're shallow in
the IR Lagoon too but I still have a good couple feet whereever I want to
go.


4" lower ;-)

It would have been 4" below the water line at speed. Pontoon boats are
a bit different than a monohull and a lot depends on how the water
flows between the pontoons. In a perfect case it would mound up right
in front of the motor like a well designed tunnel hull and you could
mount the engine very high. The problem on a turn is the hull creates
a low spot in the water and starve the prop.

Thanks, I'll check mine and see where it sets. Probably the simplest fix
would be a couple of hefty females abaft the beam!