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hi all. just curious to see if others raised there outboards up or down on the plate...i have heard this changes performance and fuel use for the better along with reproping....thanks...jim
__________________ life is good . . . lol . . . work is good . . . life is great, Jim Tatler
Jacking plates are mostly used on racing hulls to reduce drag by raising the motor to its optimum height to eek out that last mph at top end. Usually applied at speeds of +60 mph in glassy conditions.
If I understand what you're asking, Bullshipper's explanation is pretty good, but I've known several people with regular ol' boats to do it as well. Most people start with their engine at the height where the cavitation plate is even with the bottom of the hull. If you move the engine up a hole or two on the mount (if you don't have a jackplate), then you are decreasing the drag of the lower unit somewhat which will raise the RPM maybe a couple hundred and allow you to move up in prop pitch giving you more speed. As I understand it, there is kind of a sweet spot that you're looking for.
__________________ WTB: 18-22', late model CC; PM me if you got something
If he is looking for better milage then I would save $1500 per motor plate and just move the motor so that the cavitation plate is about 1" above the bottom of the hull, then use the trim tabs to optimize speed and milage working around the correct home base.
The electric jack plates are for minute adjustments on real high horsepower engines to nose out the compitition at the finish line, or to maximize results for publized perfomance reports where a lot of chest puffing and testosterone is involved.
I don't think jackplates are only for the high HP and high speed guys. Alot of guys (me included) have them on shallow water boats. The same as electric trim is set for different conditions so can a jack plate. Different engine heights for different speeds. The engine setback can also help small boat handling. I'd hate to get placed in a group of pinky ring wearing speed fanatics just because I use a jackplate. Just my experience with the jackplate.
It seems that nowadays most manufacturers mounttheir motors too low resulting in poor fuel economy and lost performance. The general rule of thumb is the motor can go up 1" for every 12" of setback. Start by taking a straight edge from the bottom of the boat to the cavtation plate with the motor at neutral trim. Mark where the edge hits the lower unit. For every hole up or down, the motor will go up or down about 1/2" - 1." With the standard transom mounted motor, the mounting bracket gives you about 6" of setback so the bottom of the cavitation plate should be 1/2" above the botom. It is definately better to be too high than too low.
If you go to any of the bass boat forums you will find that a high percentage of those guys use jack plates. They are much more common than one would think and definately not just for the racing crowd. The benefits have already been mentioned. Prices range from around $200 for a manually adjusted one to $700-800 for the hydraulic ones like this:
cavitation plate???? 
