Cavitation plate for bravo.

SSComp · 04-14-2003, 11:31 AM

I had a small strike last year on my drive. The only damage done was a hunk of the cavitation plate in the front about 2" wide and 4" long came off. Didn't even touch the prop!!

I saw no difference in cavitation problems last year running it.

Anyways, I'm thinking of grinding the area down on both sides (both drives) and leaving it. I looks like it actually might reduce drag in the trim up position.

Any thoughts on the matter?

SSComp · 04-16-2003, 11:26 AM

Nobody?

04-16-2003, 12:56 PM

I have the same situation on one of my TRS drives, and have not decided how to attack it. The "ventilation" plate serves some purpose with it's factory shape, and I suspect that the front part of the plate deflects spray down. If you grind that area away you may experience some spray coming up the transom at certain drive angles. Where is the Dennis Moore of outdrives when we need him? I am leaning toward having a replacement piece of aluminum welded on. Should not be difficult nor damaging to the drive. Bob.

Griff · 04-16-2003, 02:28 PM

I broke a corner of mine off last year as well. Ran a chunk of plastic between the drive shower pickup and the prop and broke the corner off. I still had the broken piece as it was attached to hose. Had it welded back on without any problems.

SSComp · 05-10-2003, 09:10 PM

ren3 thanks for the input.

I really thought someone would know the purpose of this plate as it relates to a go-fast since it is used on heavy boats too. Anybody else want to take a stab?

Tinkerer · 05-10-2003, 10:36 PM

What is your cavitation plate doing in the water flow at speed? Have you tried the shorter drives?

rws · 05-11-2003, 06:59 AM

Years ago on my friends old formula (215 drive) some foreign object lodged between the prop and cavitation plate and broke a chunk about 5" long off of one side .The boat labored to get on plane after that. I welded a new piece in and time to plane was reduced.Maybe with the twin you don't notice this as much.I would not want to experiment and then have to weld them back on.

Rob

SkiDoc · 05-11-2003, 07:02 AM

Switched to an imco lower(no cavitaiton plate). The differences.... More prop slippage coming on plane.....Bigger rooster tail.. But again this is the whole thing gone.

Mr Gadgets · 05-11-2003, 01:23 PM

Years ago, I added area to the cavitation plate on my outboard. Running a Merc chopper prop, it would rev to 6000rpm on take off. Adding the plate caused the take off rpm to drop to 4000rpm. I was getting more bite and still in the HP rpm range of the motor. I believe I was controlling the amount of air getting to the prop by adding a plate, similiar to the whale tales of today ( my son says I should have patented it).
So if you cut and then have trouble getting on plane or turning, well you took off too much, otherwise it may work??? But the welding bill will be three times more if it doesn't. They design them to work in a wide range of circumstances. So change it at your own risk..

Good luck

Dick

SSComp · 05-11-2003, 03:13 PM

Thanks for all the input. Keep it coming.

I've never tried shorter drives. Seems like a very expensive experiment.

The the fact the IMCO has no cavitation plate intrigues me. I can see why it tails and has a harder time coming on to plane.

I'm looking the remove only the front 4 inches of the plate. My theory is that at full speed, I hope to gain speed at the trimmed out position by assuring the plate is not digging into the water. Coming on to plane, I do not think the boat will be affected due to most the plate is still intact.