V-board motor mount

[Davey W]

I just did some quick diagrams to show what the problem was with this motor and the flush mount motor board.

The first boat shows how it was. The second boat shows where the motor sits on the lowest pin now, and the last image shows where the motor sits on the 3rd pin up from the bottom. So you can see how the original setup was causing excessive bow up tendancies.

 

[tod osier]

I am not trying to make a displacement hull boat get on plane.

I don't agree. You have a 12' boat doing 20 mph. That speed exceeds the hull speed by 3-4 times, you are on planing. T

 

[Davey W]

I am not trying to make a displacement hull boat get on plane.

I don't agree. You have a 12' boat doing 20 mph. That speed exceeds the hull speed by 3-4 times, you are on planing. T

Tod, are you implying that the estuary is a 5mph boat? 4 times the speed of that would be 20.

The boat is not on plane, not even close. But by changing the motor angle, the boat rides more the way it should be. Let Jim Donofrio chime in here. I believe his estuary does 15-16kts. That is just about 20mph. He runs a johnson 2 stroke on a motor board that David Clark mounted on an angle. The bow of his boat rides high, as it should. The bow on my boat was much more out of the water than Jim's boat rides.

Even though it is a displacement hull, the thrust angle of the motor is very important. If the angle is improper, it can adversely affect handling (more hull out of the water), it can put more wear and tear on the engine and it can also greatly increase the draft.

 

[tod osier]

I am not trying to make a displacement hull boat get on plane.

I don't agree. You have a 12' boat doing 20 mph. That speed exceeds the hull speed by 3-4 times, you are on planing. T

Tod, are you implying that the estuary is a 5mph boat? 4 times the speed of that would be 20.

The boat is not on plane, not even close. But by changing the motor angle, the boat rides more the way it should be. Let Jim Donofrio chime in here. I believe his estuary does 15-16kts. That is just about 20mph. He runs a johnson 2 stroke on a motor board that David Clark mounted on an angle. The bow of his boat rides high, as it should. The bow on my boat was much more out of the water than Jim's boat rides.

Even though it is a displacement hull, the thrust angle of the motor is very important. If the angle is improper, it can adversely affect handling (more hull out of the water), it can put more wear and tear on the engine and it can also greatly increase the draft.

I am responding to your statement that: "I am not trying to make a displacement hull boat get on plane." I was trying to clarify for you the distinctions between travelling at or below hull speed and planing. I was implying that maybe you didn't completely understand that a displacement hull can be planed and that is the what you are doing when you are making a spoon shaped displacement hull travel faster than hull speed. I'll say again that a 12-14' hull going 20 mph is not in displacement mode. I don't doubt that Jim's or anyones estuary does 15-16 knots, that is neither here nor there (other than 15 mph is a lot faster than 5).

Hull speed is defined by physics and has to do with the characteristics of the water it is moving through. Once hull speed is exceeded, the boat has to climb on plane. If it is above hull speed it is planing. You may still be moving a lot of water and the bow may be sky high, but the boat is on plane. So, yes, I would still say that you are making a displacement hull plane. I didn't say that is a bad thing or a bad way to go or that you are a bad person, it is physical characteristic that the length and shape of the hull at waterline defines its hull speed, which 20 mph exceeds by a lot.

T

 

[Davey W]

Thanks for the clarification Tod.

 

[Chris S.]

Davey,
When you put the V board on and ran it did water shoot up in the middle of the board between the to pieces of oak I put a board like yours on the refurb I am doing with bill simonson and was wondering if the water shoots up also if you are looking for a brand new 15hp 2 stroke yamaha let me know I have a number for a guy in florida that has a 9.9 a 15 and a 25 all new he gets em from time to time I gave the number to david palmer but the guy was out at the time let me know
[Inline 20110302164214.jpg]

View attachment 20110302164214.jpg

 

[Davey W]

I didn't have any water shoot up through the middle, because there is a block bolted between the motor board and transom. I had to do it because David Clark had a 5th hole drilled at the bottom of the motor board. Water did catch the sides and spray outward. Its getting the CMC plate soon anyway.