Trim Tabs or Doel-Fin

Trim Tabs or Doel-Fin

Post by Charlie Bosc » Mon, 10 Nov 1997 04:00:00


I have an 18' Robalo Center Console with a Merc 150. I am considering the
addition of either trim tabs or the Doel fin. Please give experiences with
either of them. Good and bad. What type of performance will I see?

Thanks!
Charlie

 
 
 

Trim Tabs or Doel-Fin

Post by BobN6J » Tue, 11 Nov 1997 04:00:00

There is no comparison.  The Doel Fin will get your boat to plane sooner, at a
 lower speed.  But it also will reduce your top speed, due to increased drag.
 Trim tabs will also plane you faster, at a lower speed, will add no increased
 drag, and, after you learn their characteristics, will allow you to increase
 top speed, reduce fuel usage, run a given speed at a reduced RPM, etc.  This
 is because, when used in conjunction with your outboard trim, a combination of
 t*** up the engine, and dropping the tabs (both of these in very slight
 adjustment steps) will lift more of your boat out of the water, hence less
 drag.  It does take time to learn the use of trim tabs, but they are well
 worth it.
BOB N6JUN s/v Priority Won

 
 
 

Trim Tabs or Doel-Fin

Post by Dick Luca » Tue, 11 Nov 1997 04:00:00

Quote:

> I have an 18' Robalo Center Console with a Merc 150. I am considering the
> addition of either trim tabs or the Doel fin. Please give experiences with
> either of them. Good and bad. What type of performance will I see?

> Thanks!
> Charlie

At the risk of being labelled a nay-sayer, I will describe my experience
with a Stingray fin (bolted to the anti-cavitation plate) of a Mercury
175 HP outboard on a SeaRay Laguna 20 center console.  I found no
noticeable changes in performance and finally took it off after 4 years.
It did not affect the top speed, but I did notice that when the boat was
on a plane, the fin was just above the water level.  Of course, where
the fin ends up when you are on a plane depends on how high your engine
is mounted. When I took it off, there didn't seem to be any noticeable
changes in the time to plane, rpm at plane etc.  Of course, I have no
real data to back this up, just a feeling.

When I removed the fin, I accidentally dropped it about 3 feet onto a
gravel surface and it broke in two.  The Stingray fin is a one-piece
unit, as opposed to the DoelFin which is in two pieces.  I would expect
that the one piece construction would inflict lower stresses on the
anti-cavitation plate, but when it breaks so easily after being out in
the open for 4 years, I wonder!!

I have come to the conclusion that the real advantages of the bolt on
fins are to correct for some other fault, such as underpowering.  150 HP
on a 18 footer doesn't sound like underpowering to me!

Dick Lucas

 
 
 

Trim Tabs or Doel-Fin

Post by JessB » Tue, 11 Nov 1997 04:00:00

I have a 19' Stingray with a 4.3lx mercruiser.  I installed bennet hrdraulic
 tabs before last season.  I recommend them without reservation.  They get me
 on plane much more quickly, I can stay on plane at lower RPMs, the boat does
 not porpoise at all - it used to like crazy, it takes a chop better, they let
 me compensate for cross winds or uneven loading, they are fun to play with.

They cost me around $300 at BOAT/US and it took about 6 hours to install them -
 I took my time.  Make sure you get all the tools and needed materials listed
 in the instructions BEFORE begining the installation.  Forget about the doel
 fin - its a cheap fix.

 
 
 

Trim Tabs or Doel-Fin

Post by Paul Jone » Tue, 11 Nov 1997 04:00:00

I have used both and found the doel fin helped the boat come out of the
water and was more stable at speed than without but it did not come
close to the improvement in ride/handling of twin trim tabs. (probally
directly porportionate to the cost!)
Trim tabs are definatly the answer if they are in the budget.
Good Luck