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Assembling
an Outboard Fuel System
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Every outboard seems
to have different fuel line connectors, and this is one area where we wish outboard
manufacturers would standardize. As the array of pre-assembled fuel lines and fuel line
connectors we stock will attest, this hasn't happened yet.
There are three choices in assembling a fuel
system for your outboard engine:
- Purchase an Ultra Flow Fuel System
matched to your engine. Everything you need-tank, fuel line, and quick connector for your
engine-is included. With these systems, the hose is permanently attached to the tank.
- Purchase a portable tank, then add a
Tempo Ultra Flow Fuel Line Assembly designed for your engine. You'll need to attach the
appropriate 1/4" NPT quick connector to the tank in order to connect the tank end of
the hose.
- Purchase a portable tank, a universal
fuel line with primer bulb, or a length of outboard fuel hose and primer bulb
individually. Then add quick connectors matched to your engine. For a removable hose, use
three connectors (one for the tank and two for the hose, matched to your engine). For a
hose that's permanently attached to the tank, use a 1/4" NPT pipe-to-hose barb at the
tank end, and the appropriate quick connector at the engine end.
Clamp all connections with stainless
hose clamps (Model 355222), and use Teflon tape to seal any threaded connections against
leaks. With a tie-down strap to secure the tank and a tray or rubber mat to protect the
floor of the boat, your system is complete.
Fuel
System Installation Checklist
Typical Permanent
Gasoline Tank
| The ABYC specifies that permanent
tanks must be grounded, vented to the outside, and accessible for inspection and testing.
All components must meet certain standards for mechanical strength, burst pressure, and
fire retardance. |
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Tips on
Propeller Selection
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What
They Do
Propellers provide forward thrust for a
boat under power. There are two main styles of propellers: two-to-four blade styles which
fit inboard engines with propeller shafts (sail or power), and three-to six-blade styles
which fit outboards or stern drives.
How They Differ
Propeller size is described by two numbers: the diameter and the pitch.
They are the most important measurements in selecting a propeller.
Diameter is two times the
distance from the center of the hub to the tip of any blade. In general, smaller diameters
correspond with smaller power engines or higher speeds.
Pitch is the theoretical
forward movement of a propeller through one complete revolution. Since there is always a
slight amount of "slip" between the prop and the water, the actual distance is
slightly less.
Material - Propellers are
made of either composite, aluminum, bronze, or stainless steel. Composite props make good,
durable primary props and inexpensive spares. Aluminum props are the most common, suitable
for the widest range of size, load, and rpm applications. Bronze or stainless props offer
higher performance and better durability for speedboats, tournament ski boats, and other
special applications. The following breakdown compares the materials:
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Weight |
Flex |
Repair |
Cost |
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Composite |
Least |
Little |
Not Possible |
Least |
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Aluminum |
Medium |
Little |
Easy |
Medium |
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Stainless |
Greatest |
Least |
Difficult |
Greatest |
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Bronze |
Greatest |
Least |
Easy |
Greatest |
Number of blades - With any
propeller, it is important to have enough blade area to evenly distribute engine power
across the surface of the blades so it is properly transferred into forward motion. Too
little blade area causes high "blade loading," meaning the prop is incapable of
absorbing all the power transferred to it by the engine. This leads to cavitation,
vibration, and in extreme cases, pitting. Luckily, manufacturers save you the trouble of
making lengthy calculations, and design their props to fall within a safe blade loading
range.
With increased blade area you can
decrease blade diameter, but often at the cost of efficiency at higher speeds. A
three-blade prop is generally considered to be the best combination of blade area and low
blade loading. However, when the number of blades on a prop is changed, the diameter and
pitch require minimal adjustment for the prop to remain within the safe blade loading
range. So, for all intents and purposes, three- and four-blade props can be used
interchangeably on outboards and sterndrives without a perceptible change in performance.
Wide-blade, super-cavitating, and two-blade folding props for inboard engines deserve
special consideration, and fall outside the scope of this Advisor.
Choosing the
Perfect Prop
Prop selection is one of the primary
factors which determines boat performance. Because similar-sized boats are used for many
different applications, there are a wide range of sizes and styles available. The basic
rule is to select a prop which allows the engine to reach its optimal wide open
throttle (WOT) rpm range, which is generally usually between 5000 and 5500 rpm,
depending on engine type. (This information is generally in the Owner's Manual which comes
with a new boat or engine.) |
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Mercury 9.9 Outboard
Ultra Flow Fuel
System
Tank-Fuel 55
Gallon
Diesel
Filter/Separator
Cupped Aluminum
Propeller
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