Outboard Motor: Trim Tab vs No Trim Tab

Natty Light

Petty Officer 2nd Class
Joined
Jun 11, 2012
Messages
120
18ft Triton Fish n Ski Yamaha 2-stoke carb 150

I have recently run my boat without a trim tab (came off in the fall) and with a trim tab (had it replaced in the spring.
There are considerable differences and I was wondering what everyones thoughts were to the running a boat each way.

While running WOT without a trim tab the boat seemed to run best when my motor was trimmed about 3/4 of the way out
While running WOT with a trim tab the boat seems to run best with the motor timmed about 1/4 - 1/2 of the way out.

When I say "run best" I mean how easy the boat was to drive steering and handling wise.

I haven't verified this but it seems that the boat was faster without a trim tab, but at WOT with the trim all the way out it was almost impossible to turn the steering wheel.

With the trim tab on, WOT and trimmed all the way out, the steering is still harder than cruising speeds, but noticebly more managable than running without a trim tab.

I have also noticed some boats have just a tab-less plate installed where a trim tab would normally be. Is there a benifit either way?
 

UncleWillie

Captain
Joined
Oct 18, 2011
Messages
3,995
Re: Outboard Motor: Trim Tab vs No Trim Tab

Are we talking about a horizontal Hydrofoil/Wale Tail mounted to the AV plate?
Or trim tabs on the Transom?
Or a Vertical Trim Tab behind the Prop?

The Vertical one by the prop is helpful with manual steering.
With No-Feedback and Power Steering it is usually deleted.
 

Natty Light

Petty Officer 2nd Class
Joined
Jun 11, 2012
Messages
120
Re: Outboard Motor: Trim Tab vs No Trim Tab

Are we talking about a horizontal Hydrofoil/Wale Tail mounted to the AV plate?
Or trim tabs on the Transom?
Or a Vertical Trim Tab behind the Prop?

The Vertical one by the prop is helpful with manual steering.
With No-Feedback and Power Steering it is usually deleted.

The vertical one above the prop on the underside of the cavitation plate.
 

UncleWillie

Captain
Joined
Oct 18, 2011
Messages
3,995
Re: Outboard Motor: Trim Tab vs No Trim Tab

I was confused on your wording.
Most people don't remove the Tab and try running without it.
It is also the Anti-Corrosion anode for the prop. (One of the "Zincs".)
I will assume, "It came off in the fall", means it broke off!

Assuming a Non-Assisted steering system;
The faster you go the more force the steering is going to need.
The Prop trim tab counteract the tendency to of the engine to pull to one side. Usually the Left.
As you slow down, the steering forces will get lighter and the trim tab will become less effective.
You should see no noticeable effect on top speed.
Boats with power steering usually do not have a Prop Trim Tab.
Power steering overrides any feeling of the drive pulling.

Your experience sounds normal and it seems you prefer the assistance of the Tab.
 
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