Compression Plate for Shallow Running

[FishNette]

When I purchased my flounder boat, it had a poorly made compression plate(hammered edges) on the outboard, so I decided to take it off and purchase a new one. After shopping around, I didn't find much to choose from, and the one I liked was $345(ouch).

So I spent a couple of hours and $35 to make my own. Pics attached. After running it Saturday, I was impressed. It worked really well and kept the prop from cavitating at all. I think it needs to be moved a little further forward to eliminate a little too much water spray between the transom and the motor, but once it is planed out and trimmed correctly, the spray goes away.

I'll continue to tweek on it until I get it near perfect.

I'm considering building a compression plate and hydrofoil combination unit. Basically it will be a compression plate with wings. I'm hoping for no cavitation when running shallow with the motor raised and quicker plane times. If anyone has a shallow running boat they want to try one on, let me know. Hoping for a 115hp to a 150hp for testing. Prefer someone who goes out a couple of times a week. If you have a boat that cavitates alot when running shallow, you need something like this.

[Gulfcoast13]

Looks like a heck of a job. WTG!!

[FishNette]

Try rolling the front up a little . Like a ski

Good idea. Thanks!

[Little Boat]

Looking good. You mentioned the $345 manufactured plate, what is the difference between it and the one you made?

I always enjoy seeing the mods that people make to their boats. Maybe some day I'll be doing this stuff too.

[FishNette]

Looking good. You mentioned the $345 manufactured plate, what is the difference between it and the one you made?

I always enjoy seeing the mods that people make to their boats. Maybe some day I'll be doing this stuff too.

Theirs clamps to the lower unit rather than bolting. Some people do not want to put holes in their motor, which is understandable. My 50 hp is a 1975, the holes were in it when I got it, so I just used the same ones.

Here are pics of the $345 unit:

[Rollo]

I have a 115 Johnny used on most weekends and a 17.2 Bay Hawk...I like runnin shallow.No JackPlate though!

[fuzzy]

Looks like my Nedski except the fronts turned up on mine.

[Little Boat]

Theirs clamps to the lower unit rather than bolting. Some people do not want to put holes in their motor, which is understandable. My 50 hp is a 1975, the holes were in it when I got it, so I just used the same ones.

Thanks for the photos. I like it bolted on rather than clamped. What's a few holes in the lower unit, no big deal.

[FishNette]

This is what I run on my 18 ft Flattie with a four blade prop, works great. I never had a cavitation problem but the hole shot is, well you might want to sit down.

Incorporate this design on top of yours and your set!
Nice work!


here is a link for more pics.

http://www.cobramarine.com/cobra_marine_hydrofoil_stabilizer_edge_pro_series.html

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Thanks for the comments and pics.


Cavitation or prop blowout is not the only problem a compression plate cures. It also helps ensure there is a sufficient supply of water to your engine's water intake ports for cooling the engine. Running the engine higher out of the water can cause the water pump to starve. Generaly, if the cavitation plate is higher than the bottom of the boat, you should have a compression plate installed. Tunnel hull designs help cure this problem as well, bet even they can experience the ill effects of unstable turbulent water flow across the intake ports.


Imagine a compression plate that also serves as a foil for quicker planing. Stay tuned for more pics. I'll be builing a prototype this weekend.

[FishNette]

We have a 200 ton press brake and can press brake it for you if need be.
My 115 yami has low water pick up and the skiff has a tunnel and pontoons on the back so the water is forced that way, Works out great.
But your design would probably work out better on mine too, who knows. I'll test one out if you want.

Thanks for the offer, but the next units will have a "tail" incorporated with the compression plate, so it won't be the same design. I may be willing to trade one for some knowledge about, and a trip around, the Diversionary Canal.???