Engine height question for V21

[garbubba]

I'm confused why you think the plate in the water would cause the motor to pull on the transom? The motor pushes the boat, more drag at the motor would just mean a little less push, but no more pressure on the transom.

Or am I missing something?

[Destroyer]

Originally Posted by garbubba

I'm confused why you think the plate in the water would cause the motor to pull on the transom? The motor pushes the boat, more drag at the motor would just mean a little less push, but no more pressure on the transom.

Or am I missing something?

Since there is a pivot point at the engine mount there are different torque forces being applied to the transom. While you are correct that the main propeller force is being applied in a direction that pushes the boat forward through the water, there is a lesser force that is actually either pulling or pushing on the transom. While this force does not diminish the driving force through the water, it does do other things depending on how the engine is trimmed. Thus, if the engine is trimmed high, this force has a tendency to actually pull the bow of the boat up out of the water, and if the engine is trimmed too low, it will cause the bow to dig in too much. The plate in the water at the wrong angle will increase this force since it equals additional friction of the engine moving through the water.

[bgreene]

Originally Posted by garbubba

I'm confused why you think the plate in the water would cause the motor to pull on the transom? The motor pushes the boat, more drag at the motor would just mean a little less push, but no more pressure on the transom.

Or am I missing something?

Destroyer explains it with his last sentence and also picture it this way.

With the cav plate under water, when engine is trimmed up for efficient cruising, the cav plate is then running through the water at an angle - downward facing.
The water therefore is pushing against the cav plate.......same as if you're in a swimming pool and running your hand " flat" under water - no pressure right ?
Turn your hand at an angle........but keep it going straight and you'll feel the water pressure and resistance against your hand.
Now imagine the pressure on your hand if you could push it through the water at 30, 40, 50 mph. The outboard is therefore generating " pull" on the transom when the motors trimmed up. I can't tell you how many lbs of force, but it is drag, no question about it.

This is why performance riggers like the outboard higher, so the cav plate is close to even with the surface rather than below.
Got it ??

[macojoe]

Thats why the cav plate is to be even with the bottom of the boat, the boat blocks alot of the drag you are speaking about. There is going to be drag no matter what you do!!!! So suck it up and enjoy!

[randlemanboater]

Sounds pretty perfect to me...raising it any more MAY cause you to have more cavitation problems when turning at slower speeds.

I think the drag of the motor would put rearward pressure on the motor opposite of the foreward pressure of the thrust from the prop.