What do "Jack Plates" do?
 

Are they simply to get the engine higher? If so, why not just mount
it higher?

What do "Jack Plates" do?
 

On Sep 5, 12:04*pm, wrote:
Are they simply to get the engine higher? *If so, why not just mount
it higher?

It also sets it back, changing the "length" of the boat.. I don't know
much more about Jack Plates than that, but if Shortpants sees this
post, I am sure he can help you out...

What do "Jack Plates" do?
 

wrote in message
...
Are they simply to get the engine higher? If so, why not just mount
it higher?
I was of the impression that a jack plate lets you mount the engine higher
without having to redo the transom. In other words, you can't mount the
engine higher if there is no transom there to bolt it to and thus the need
for the jack plate. Some jack plates, I've seen also give you the ability
to lift the engine up to navigate shallow water. Would work better than
tilting the engine.

Tom G.

What do "Jack Plates" do?
 

On Sep 5, 12:04*pm, wrote:
Are they simply to get the engine higher? *If so, why not just mount
it higher?

For one thing, if you don't have a jackplate, the motor must be low
enough so as to not cavitate in chop. With a jackplate, when
conditions are good, you can get the motor up out of the water
somewhat reducing drag, and also when navigating shallow water. If you
were to simply tilt the motor instead, it would tend to push the stern
of the boat down, and possibly scraping bottom in shallow water.

What do "Jack Plates" do?
 

On Fri, 5 Sep 2008 09:04:35 -0700 (PDT),
wrote:

Are they simply to get the engine higher? If so, why not just mount
it higher?

It's a little more complicated than just setting the engine higher (or
lower for that matter) but that is a reason.

Jack plates come in two flavors - fixed mechanical and movable
hydraulic. The fixed mechanical type is used exactly for the reason
you mentioned - to set the engine either higher or lower depending on
needs.

For example, my Ranger bay boat is a 'tweener. The specs call for a
20" shaft, but due to the design of the hull, 20" shaft isn't exactly
correct 22" would be more sufficient. When I had a 20" shaft FICHT on
it, the boat ran fine on mostly smooth to very light chop, but any
thing heavier created a situation where cavitation was a problem. Also
because it was a 'tweener, the boat had zero bow lift when coming up
on plane - it would hit around 3,000 rpm and accelerate to 4,000 in a
blink of an eye - the boat literally leapt out of the water coming up
on plane.

I had thought of using a jack plate on the FICHT, but it didn't bother
me much and as I had two other boats at the time, it wasn't worth
getting into.

When I repowered, I decided to go with a 25" shaft ETEC and just
adjust out the extra two inches by mounting it a bit higher. That
didn't work - now I had the opposite problem - too much shaft in the
water instead of too little. It sounds odd that height placement was
that critical, but on this boat, it is - don't ask me why. So a
mechanical jackplate was installed and I got the engine exactly where
I wanted it to be - end of problems.

One side effect of using a jack plate is engine set back. The axiom is
that for the same horsepower and hull configuration, a longer boat
will also be slightly quicker, a little more efficient and much better
trim control - all of which are true. You can get them in a variety
of setbacks, but the most common are 3 and 6 inches.

Hydraulic jack plates serve the same function as mechanical jack
plates, but are dynamic - you can adjust for differing conditions like
sea state, shallow water running, weather - etc.

With respect to adjusting height by modifying the transom, certainly
you can do that, but it's costly and you can achieve the same effect
cheaper with better results.

What do "Jack Plates" do?
 

Short Wave Sportfishing wrote:
On Fri, 5 Sep 2008 09:04:35 -0700 (PDT),
wrote:

Are they simply to get the engine higher? If so, why not just mount
it higher?

It's a little more complicated than just setting the engine higher (or
lower for that matter) but that is a reason.

Jack plates come in two flavors - fixed mechanical and movable
hydraulic. The fixed mechanical type is used exactly for the reason
you mentioned - to set the engine either higher or lower depending on
needs.

For example, my Ranger bay boat is a 'tweener. The specs call for a
20" shaft, but due to the design of the hull, 20" shaft isn't exactly
correct 22" would be more sufficient.


Well, well, well...a 20" transom on that Ranger. Now isn't *that*
interesting.

What do "Jack Plates" do?
 

On Fri, 5 Sep 2008 09:04:35 -0700 (PDT),
wrote:

Are they simply to get the engine higher? If so, why not just mount
it higher?

Mine has a hydraulic jack plate as well as trim tabs. The plate can
vary the position of the motor based on current circumstances and
conditions. My main use is in shallow water - I can raise the jack
plate while lowering the trim tabs - slowly build up some speed until
the trim tabs take effect then hammer down and I'll be on plane in
about a second.