Add a Hydrofoil
Is your boat performance a little weak? Hype it up by installing a hydrofoil.
by Steve Noury
March 1, 2005
Installing a hydrofoil on your outboard motor is one of the easiest and least expensive ways to
enhance your boat's performance. The boat will get on plane quicker, which not only gets you going
faster, but saves on fuel consumption. Other benefits include better control, sharper turns and a
better ride. If your motor has a tendency to cavitate, a hydrofoil can significantly reduce and
possibly eliminate this problem.
Step 1 - For the purposes of this article, a SE Sport 200 Series made by
Sport Marine Technologies Inc. is
installed on a 90-hp outboard. It's important to make sure you choose the right model, depending
upon the size of your engine. Most manufacturers make their product for motors ranging from 25 hp
all the way up to 300 hp. The necessary hardware will normally be supplied, and the only tools
you'll need will be a power drill, a screwdriver and a socket wrench. First, center the hydrofoil
on the top of the cavitation plate. Leave at least 1/4-inch metal (1/2 inch preferred) from the
holes to edge of the cavitation plate. Don't position so far forward that the hydrofoil tilts
upward. Mark, and then drill the four 1/4-inch holes.
Step 2 - After drilling the holes in the cavitation plate for the hydrofoil, you
need to insert the 1-inch bolts in the forward holes, and also the 1 1/4-inch bolts in the rear
holes, all four from the bottom up. Place the 3/32-inch rubber washers on the forward bolts, and
the 3/16-inch washers on the rear bolts between the hydrofoil and the top of the cavitation plate.
It's possible to do the next part by yourself, but because of the size of the hydrofoil and the
balance needed, it's much easier if you have two people to do the task at hand - one to hold the
hydrofoil in place and another person there to insert and hold the bolts and washers in place until
the lock nuts are attached.
Step 3 - Place the steel washers and locking nuts on top. Use the lock nuts only
once in the assembly. Reusing them can cause the locking insert to fail. If, for some reason, you
have to re-use the lock nuts, then stainless-steel replacements can usually be found at your local
hardware store for the job. At this point, don't tighten the nuts completely, and check to be sure
that the hydrofoil is properly aligned now that all four bolts are attached. If the alignment looks
a little off, you may need to re-drill some of the holes. Most of these products supply a template
for proper placement, so it's best to use it in order to avoid any possible mistakes.
Step 4 - Using an alternating torque pattern, begin with the front holes and start
to slowly tighten all of the bolts in rotation. By doing this, you'll get even compression, and
because of this the hydrofoil will properly seat against the cavitation plate. You need to tighten
the bolts in each of the holes to the point of being snug, and then add an extra turn for good
measure. Once you're finished tightening the bolts, the hard part is out of the way. You're done
with the installation, with the only exception of seeing how well the hydrofoil works for you on
your boat with an on-water test. Try them out, you're sure to be pleased with the results!