Trim

In flat water, trim your outdrive to give you the greatest speed.
If you're not loaded too heavily, that will usually be at the most trim you can achieve without ventilating the prop. I would usually trim out until I heard the prop ventilate- then trim it back in just a bit until the ventilation stopped.
 
Welcome to CSR!

You trim by feel.
The correct amount of trim varies boat to boat.
Here is a basic run down for calm conditions and normal cruising:
Step #1) Trim all the way down.
Step #2) Get up on plane.
Step #3) get going the approximate speed you want to go.
Note the rumbling feeling like your bow is being driven into the water. This feeling is from your bow being driving into the water.
Step #4) slightly trim up and note any difference in feel. Repeat until you no longer get that rumbling feeling then stop.
 
In addition to the previous post, also note your MPH and Tachometer. Once you start to trim, you will note that both will begin to go up, not much but your speed and RPM's will increase. Continue to trim until you begin to see both of them start to fall off, then you have gone too far. At the proper trim your boat will run at it's most efficient level. The trim will vary depending on weight and distrubution.
 
Presentation said:
um.....just a guess, you are asking about Cavitation?

http://en.wikipedia.org/wiki/Cavitation

For boats like ours this means don’t trim up too far.

Its notable and obvious.
Click to expand...
Ventilation means you suck in air, and the prop loses its "bite" because it is sized for pushing water and not air. Cavitation is the formation of water vapor bubbles (as opposed to air bubbles). Cavitation is harsh and can damage the propeller. Air bubbles do no significant harm other than reduce performance.
 
Ventilation is the correct term for what happens when you overtrim a drive and start sucking air...

Read here:

Ventilation and Cavitation
Ventilation occurs when surface air or exhaust gases are drawn into the propeller blades. The load on the propeller is reduced by the mixing of air or exhaust into the water steam causing over revving.

Anti-ventilation Plate: Large plate cast into gearcase housing directly above propeller. Helps reduce surface air from being pulled into blades.

Cavitation: The aeration (bubbling) and boiling effect of water caused by creation of a low pressure area. Generally caused by a solid shape (propeller blade) passing through the water, in such a position and speed, that a low pressure area is formed due to the inability to move through the water in nonresistant manner. An example is, a propeller blade that has a rough edge would not cut efficiently through the water, thus creating a low pressure area. If the pressure drops below the vapor pressure, a cavitation bubble will form in that region. These bubbles will collapse when they reach the higher pressure region of the blade. This causes a rapid change in pressure and can result in physical erosion. You may notice burns (erosion) at some area on the face of the blade.
 
The biggest factor you will find regarding trim on the 18 footer will be how choppy the water is. The rougher the water, the more down trim you will need to run to keep the front end from pounding. You can lessen this somewhat by moving some weight (people) up front in the bow area. Basically use as little down trim as possible at cruise speed to minimize bow pounding. In the real world, Powell is sometimes rough in the canyons and you will use a lot of down trim and less than full throttle.
 
WOW! Ya'll are great with the advice and help! And scott yea Powell(halls) is were we go 90% of the time.
 
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