I have a 21' Kenner V-Tunnel hull with a long shaft Johnson 150 HP motor. I want to add a cavetation plate to the motor. Any suggestions on which one? I've had a Dol-fin before and wasn't to impressed.

Attwood makes one called a Hydro Stabilizer. It is a 2 piece . I have one on each of my boats even looks good.
A high speed turn could be actually more dangerous with a stablizer. I believe they are designed to get you on plane faster as to cause less strain on your engine. Getting on plane is high stress to a engine. High speed turns are dangeres in their self.

I have that Attwood too and like them better than the Doelfin. The Attwood is swept upwards and is perfect for my deep V.

hers a 4 page discussion on cav plates
http://www.2coolfishing.net/ttmbforum/showthread.php?t=9437&highlight=cavitation+plate
Spend the $ and buy a custom you won't be disappointed.

Don't run a doel fin or any other cav plate you find in a catalog or at any outdoor store. I have had 4 shallow water bay boats and you need a true cavitation plate such as the Shallow Blaster.

I like the aluminum casting one that Bob's Machine makes and sales. These are strong enough on there own that they don't bust up the original cavitation plate on the motor so bad from the force the water puts on them when you take off.

The plastic ones and the thinner aluminum ones just rely to much on the motor's plate to help support them to add the extra force needed for a better hole shot and slower plaining speeds.

Bad thing with Bobs is the price at around 60 bucks if I remember right. These are really great plates though. I would not mount anything else on a motor though as I have had to weld up way to many cavitation plates that had the others on, that the motor was used much at all. The bigger and or the heavier the rig, the worse they will be about putting extra force on the cavitation plate area. You extend this with these add on's, make sure its a stout unit if you have a healthy boat. These flex much at all is when they bust up and crack the cavitation plates on the motor...

Many of the other brands have the back edge of them angled or rolled down somewhat too. All these cavitation extensions make a motor want to dig in and pull the back of the boat down bad when you go into reverse and stand on the throttle much at all. Real bad if you have the trim tucked down. You add some of these with the rolled over and angled down back edge they really are quite bad no matter the trim angle. The Bob's unit is straight flat and supports itself quite well and if you have the motor trimmed straight vertical off the water it want dig in.

I had a pair of aluminum ones {trim tabs} that attached to the rear of the boat rather than the motor, had an adjustment with a knurled screw on it. It was on an aluminum v bottom starcraft with a 70 horse engine. It planed out so well it slid sideways in the turns. I loved the way that boat ran. My two cents.

Thanks for the info guys. I'm going to the Boat Show today and will look for Bob's.. Does a cavetation plate help with fuel economy?