What is correct mounting height for 13' v hull j-boat w 9.9 outboard

[carter432]

I have a 13' aluminum john boat (v-hull) I have a 9.9 Nissan outboard. I have it mounted to the transom, but under full speed, water is sprayed over the rear transom into the boat (on the port side), small amounts but they add up. Next I raised the motor so that the cavitation plate is at the same height as the bottom of the boat. But this made more water come over (on opposite side)??? Can anyone advise me on how to correct this?

Thanks,

Michael

[gonzo]

First, it is an antiventilation plate. It prevents air from being sucked by the propeller. The bottom of the plate should be about 1/8" above the bottom of the boat.

[pistnbroke]

like gonzo says the plate should be just above the water when you are on the plane...does this motor have enough grunt to get you on the plane 15 mph + ?
Is there a sounder transducer kicking up spray ...go faster leave the spray behind ....!!!

[carter432]

Thanks for the correction on the anti-ventilation plate. The 9.9 Nissan gets this light boat up on plane quickly and with ease. I'm just trying to figure out why the water is spraying out so much to the sides and a little of the rear of the transom. If I place a plate that overlaps the transom about and inch, would this be acceptable to prevent the water coming over or do I need to keep adjusting the height???

[masalai]

Adjust the height as Gonzo says... I do not know if it is an illusion in the photo of the lower part of the engine but it appears that the propeller may be pointing down? make sure the tilt has the anti-cavitation plate horizontal and the propeller pushing parallel to still water surface when the boat is up on the plane...

[pistnbroke]

Is the edge of the hull at the bottom of the transom sharp or rounded as a rounded edge can pull water up....can you get hold of any fins to add to the anti ventilation plate as this may change the flow....As yet you have not said if he spray comes from the engine or the boat ?

[tunnels]

Originally Posted by carter432

I have a 13' aluminum john boat (v-hull) I have a 9.9 Nissan outboard. I have it mounted to the transom, but under full speed, water is sprayed over the rear transom into the boat (on the port side), small amounts but they add up. Next I raised the motor so that the cavitation plate is at the same height as the bottom of the boat. But this made more water come over (on opposite side)??? Can anyone advise me on how to correct this?

Thanks,

Michael

when setting up a outboard you need a starting point . The underside of the cav plate on the out board needs to be about 2 mm above the level of the bottom of the boat .Lay a straigh edge along the hull bottom and past the outboard the plate on the motor need to be the same angle as the straigh edge s well wedge the motor of the adjustments cant give you the correct angle !!
This is a good start point if you turn from one side to the other the motor at speed and exsperiance cavitation then it could only need to drop the motor just 2 mm at a time till it dosent cavitate any more . It could happen going one way and not the other as well .
The angle of the motor will act like a power tirim Nose up or nose down ma need to shift weight inside the boat to trim it properly . Small boats are not easy to trim properly . The smallest amount of weight shift and makes a big differance .