Torque Tab/Speed

[Dingie 2]

Over the years a few members have talked about seeing speed gains from 1-3 MPH when they ran allison type torque tabs. Can anyone post a pic of what this tab looks like ? Would a 55 MPH boat see any gains running this type of Tab ? Yamaha makes a tab without a skeg do you guys think this would help at all ? Joe R

[mackeral5]

joe, I believe you're talking about 2 different trim tabs---the allison style trim tab is installed on the trailing edge of the skeg whereas the yamaha tab you are talking about is the one under the cavitation plate. I've considered installing a trim tab on the skeg but I haven't gotten around to trying it out.

Bob's Machine makes a skeg mounted trim tab which can be welded or riveted on.....


Tame that torque! Bob's TORQUE TAMER will straighten out the high-speed steering pull that today's high-pitched propellors produce when running at high transom settings.

http://www.bobsmachine.com/images/misc7.JPG
Pop rivet version
http://www.bobsmachine.com/images/misc7b.jpg
Weld version
The paddle-wheel flow produced by the submerged part of such a propeller when much of the top half is out of the water swings your motor sideways (to starboard for right-hand drives) harder the faster you go.

[David]

I doubt you need a torque tab with a 55 mph boat. Are you running the engine extremely high?

[150aintenuff]

I doubt you need a torque tab with a 55 mph boat. Are you running the engine extremely high?

never seen any gain on a sub 60 mph boat unless you have incdredible torque steer and your engine is dog trackig badly...

[Dingie 2]

I have read that the torque tab can improve prop slip buy redirecting water to the prop.I also wondered if the factory anode skeg type tab mounted under the cavitation plate could interfer with water flow being it is mounted so close to the prop ? I wasn't thinking of installing a torque tab to improve steering ,I was wondering if is would improve speed ? I noticed that a lot of the hi performance lower units have some kind of torque tab and have flat anodes mounted under the cavitation plates. Joe R

[David]

Most motors have a small tab above the prop to counteract prop torque. If you run the engine high, this tab is out of the water. The resulting torque from the prop tries to turn the boat. So you wind up steering a bit to go straight. The lower unit is a few degrees off being in line with the boat. This scrubs speed. A torque tab removes steering torque, and lets the motor run straight.