Removed Hydrofoil (Whale Tail Thing) and gained a few MPH

So, we have had a whale tail on the 25 hp 'rude (on a 16" V mirrocraft w/ decking) for many, many years - After reading a bunch of opinions on here I decided to see if I could get a few more MPH out of the old girl


It worked - top speed increased about 3 mph

Boat still come up on plane at the same rate

Notice very little difference other then it turns a little more sharply

Anyone need a very use hydrofoil?

Those things and the "Smart Tabs" are for folks that don't know how to operate a boat and are mostly gimmick items.

+1. Not surprising, really. The whale tail should be out of the water along with the anti-vent when the boat is on plane. As a result, it doesn't/shouldn't effect the boats performance, except perhaps at very low speeds. If it does, it's only because the tail is in the water, creating drag, where it shouldn't be. So basically, the only way they can influence your performance is if they're being used incorrectly, and when used properly, they're out of the water and therefore make no difference one way, or the other. By removing it, you reduced the drag crated by your lower end and picked up a few mph. You may even be able to pick up a few more by ensuring that the AV plate is in fact breaking the waters surface at planing speeds. You can either clamp the motor higher on the transom such that the AV plate is level, or slightly higher than the keel and/or devise a jackplate/transom riser to do so. I recently built and installed a jack plate on my 14' tinny running a '66 20 hp and it improved handling and the ability to get on plane as well as allowing me to run in shallower water than before.

What is you top speed? I'm curious because we have the same boat. Even though I'll be running a 40 it will help me get an idea of what to expect when I finally get the thing in the water.

moberg12 said:

What is you top speed? I'm curious because we have the same boat. Even though I'll be running a 40 it will help me get an idea of what to expect when I finally get the thing in the water.

Click to expand...

Right now with full decks two TM three batteries and the console, etc (the boat is heavy) it tops at at just around 24.5 mph one adult and one 4 yr old

I am running a four blade aluminum prop (I forget the pitch)


With a 40 you should be around 35 mph depending on your weight


These are pretty heavy hulls and wide so they are awesome fishing boat - just not real sped demons

I agree the Whale Tails often do more harm than good. I don't agree with the opinion on Smart Tabs ( or the many other well done tab systems).

Every one is entitled to their own opinion, of course.

If you have to get your boat up and on plane in ten or so inches of water ( try Texas Salt flats and most other coasts)...tabs ( any tabs) are worth their weight in gold.

regards, Rich

Never saw the point of the whale tail, puts a lot of stress on a little area with the hopes of big gains. A lot of people have them up here.

Tabs if mounted correctly can have an effect - but it depends largely on the hull design and their installation.