Probably the most common question we get at the shop and on the bulletin
boards we frequent is, "What's the best setup for my
boat?" I would like to tell you that there is a secret
formula for success and there is....Hard work + trial and error = 1
dialed in rig. There are three considerations in selecting your
setup. Engine Offset...engine height...and prop selection.
Engine Offset:
Your engine acts as a lever to lift your bow and reduced wetted surface
area on your boat. The farther back your engine is, the more
leverage it is able to exert as it moves farther away from the center of
gravity of your boat. Another feature of offset is that as you
move the prop away from the pad you give the turbulent water coming off
the pad a chance to recollect. This feature can result in better
prop efficiency as the prop has a better water stream to bite
into. Engine offset is achieved in two ways. First, a
manufacturer can recess the pad (or running surface) from the
transom. You can also install a jackplate on your boat to increase
offset. But before you start bolting jackplate to jackplate there
are potential negative trade-offs with additional offset. As you
move an engine farther back you can actually enter dead spots in the
water stream coming off the pad. Yes, on some boats a ten inch
plate will not perform as well as an eight. Also, as you move the
engine back you can create some obnoxious handling
characteristics. Excessive bow lift during running and holeshot
and downright dangerous turning performance. For the purpose of
discussion we will consider V6 motors on boats 17 to 22 feet. As a
very general rule, most boats use plates from 6" to 12".
Usually longer boats and bigger motors like more offset. Check
your manufacturer's warranty before installing a plate to make sure you
are not going to void any portion of your warranty.
Engine Height:
Boat speed is simply the result of prop efficiency and forward thrust
versus friction (wetted surface area). You are constantly trying
to get your boat to run on a smaller wetted area and you accomplish this
with the leverage your motor and prop can exert. But there is
another component of friction. That is the gearcase of your motor
itself. Today's new motors have very hydrodynamic gearcases as
compared to the motors of say ten years ago. But if you can raise
your motor higher you will reduce the actual amount of gearcase in the
water and thereby reduce friction. But here's the rub. As
you raise the engine you lose leverage. If you raise the engine
too high you lose bow lift and your rig will fall on its nose and run
slower. For any combination or rig, prop, jackplate and load
characteristics there is a "sweet spot" or ideal engine
height. But be careful - as you raise your engine - waterflow to
your lower unit water cooling pickups is reduced. I strongly
recommend that you have a water pressure gauge on your boat if you
are going to use a jackplate. Your dealer can tell you what
minimum water pressure you must maintain at wide open throttle.
Also keep an eye on your RPM's as they will increase as your motor is
raised. Don't exceed manufacturers' rev specs if you want to
maximize the life of your motor.
Another question is.."will a nosecone or
CLE gearcase make my boat faster". The answer is.."it
depends. That style gearcase isn't faster by nature. But if
you could raise your motor higher (except you lose water pressure), the
low water pickup will allow you to do so. The shape of the
gearcase isn't for speed, it's to prevent an extremely dangerous
condition called blowout. Most manufacturers' gearcases are
subject to blowout at speeds approaching 80 mph. So it's something the
average Joe doesn't have to worry about.
Prop Selection:
Here's the one that runs people ragged. Today there are a number
of great high performance props on the market. But what runs great
on your buddy's Bullet might be a dog on your Champion. Let me
state this very clearly. Each different hull design on the market
has its own unique lift characteristics and requirements. It all
comes down to trusting a qualified dealer who had direct knowledge of
the hull you are using and what features (speed, rough water handling,
etc.,) you value most. There is only one rule in prop
selection. TRY BEFORE YOU BUY! You can spend $1500 on three
different props and not have the right one. If you can't find a
dealer who will let you run the prop before buying it - keep looking.
The Setup:
If you will check our article on this website on setting
up the Yamaha TRP....guess what? It's the same basic procedure for
setting up any engine. A few words of caution. Don't trust
anything besides GPS or radar. Your speedo is a joke (unless you
dropped a couple of C notes in a Gaffrig setup.) Keep notes on
every run that include holeshot, top speed, lift and handling, max
RPM's, water pressure at WOT and general impressions. Somebody
asked me the other day if it was a good idea to publish our
"secrets". Well it's not about secrets, it's about hard
work. Those dealers who are not willing to work for their
customers won't change no matter how many "secrets" you tell
them.
Good Fishing,
Rico
Silvera Nichols
Marine |