Honwave transom modifications?

[Sailpower]

Hi, I've changed my inflatable to a 3.8m Honwave airfloor, and want to use my Johnson 9.9/15 hp 2 stroke on it, I've hit a small problem with the transom height - the clamp to cavitation plate on the Johnson is 17.5 inches, and the standard height of the Honwave transom is 16 inches in the middle, although it sweeps back up to meet the sponsons at about 17.5 inches at each side - in other words the centre of the transom drops down by 1.5 inches.

I can get maybe 1/2 inch by lifting the transom clamp up as hitch as the pad will let me, but really I need to extend the transom back up to give me the optimum height for the cavitation plate in relation to the keel. Anyone got ideas for how this might be done? Sandwich the transom between two sheets of plywood and put a stringer in the gap?
Plan B is to run it with the motor deeper than it should be!

Thanks in advance!

 

[Sea Rider]

Will only need to raise transom accordingly if experiencing water splashes over engine at wot. Trim to a hole that sits engine on transom at 90 deg while sib rides paralell to sea level once on plane. Distribute deck weight evenly to achieve this condition.

For a perfect set up read points 1-7 throughout fully to understand each concept.

http://www.rib.net/forum/f50/abc-sib...nes-58373.html


Happy Boating

 

[Sailpower]

Thanks, very interesting article. I had been assuming that the 'dry' set up was to get the anti cavitation /ventilation plate level with the bottom of the transom / keel, but I take your point that determining if the OB needs to be moved up or down can be judged by the way the waterflow hits the deflection plate. The snag I have is virtually no adjustment to experiment with - can't drop it lower than 1.5 inches below the keel, and can only get about 0.5 inch higher to try out.
I'll have a try out anyway and report back.....
thanks

 

[Sea Rider]

Thanks, very interesting article. I had been assuming that the 'dry' set up was to get the anti cavitation /ventilation plate level with the bottom of the transom / keel

The dry set up is one side of the coin, the wet side is the other side of the coin which is not stated on any owner manual, word of mouth, read it somewhere else. Was dialed under trial & error extensive water experimentation under ideal water lab conditions. The issue with the dry set up is that you don't take into account, it's not important to no one the height where water flow at speed passes through lower leg.

Happens that the wet set up gives the exact SHS (Sweet Height Spot) for any given brand or engine HP to achieve better top performance than setting an engine under the dry set up. Follow guideliness and check if water flow passes over and under small water deflector plate and post back your findings.

Happy Boating