Boat Fuel Systems, Lines & Connectors

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Lines & Connectors How-To's

Article on the proper way to boat fuel line to fuel tank.

Connecting the Boat Fuel Line Assembly to the Gas Tank

If you own a boat and feel proud of taking it out into the ocean or river every weekend, then you should also know how to take care of its various parts when the time comes. Suppose you are in the middle of the ocean and your boat breaks down, and ... read more then you will be the only one ready to repair the boat quickly. You can call people for help, but they may take a long time to arrive. One of the most important parts of a boat that every boat owner should know about is the boat fuel system lines and connectors. The fuel line assembly is a special fuel line with a primer bulb in the center that connects the fuel tank with the boat engine.

Outboard Motor Fuel LineThe fuel line assembly can get old after some years of use, may deteriorate, get cracked and can start leaking the fuel. One of the symptoms of leaky fuel line is that the engine does not start as soon and may stop in the middle. Also, you may smell the gas leaking from such a cracked fuel line. If the crack is not so prominent and visible, you can inspect it by holding the fuel line in your hands, and if your hands get stained by fuel, then you know there is some leak.

What Tools and Parts do I Need for Repairing Marine Fuel Systems?

In the case of fuel leakage, it becomes crucial to change the fuel line assembly for your boat as soon as possible. For this, you will need some basic tools such as an ike 5/8” wrench, new fuel line assembly (with a primer bulb fitted in), Teflon tape and fuel tank fittings. You can use either the Teflon tape or liquid Teflon – both are good sealants. In general, there are two types of fuel line assemblies – one for overboard use and another one for using in the boats with enclosed engine room. The fuel line assembly and fuel tank fittings vary for different boats, so you should ask your local boat repair shop for the parts that are suitable for your boat.

Fuel Tank

Change the Fuel Tank Fitting

First of all, you will have to replace the fuel tank fitting. You can use the 5/8” wrench to unscrew the old fitting out quickly. If the fitting is jammed, then you should not use excessive force on it, but instead drop some mineral alcohol on the fitting threads, wait some time and then try again. Once your old fitting is out, you can wrap a little Teflon tape on the threads of the new fuel tank fitting before screwing it back. Make sure you tighten the fitting using the 5/8” wrench, but not too much as it may crack the plastic fuel tank portion.

Change the Fuel Line

The first thing you should check on the new fuel line is the arrow on the primer bulb. The arrow on the bulb should always point towards the boat motor (engine). This is because when you use the bulb to pump the fuel, it goes into the direction of the arrow. Take the fuel tank end of the fuel line and firmly plug it into the fuel tank fitting. Similarly, you have to take the motor end of the fuel line and then plug it into the motor fitting securely.

Dispose off the Old Fuel Line and Fittings

Now that you have installed new boat fuel system lines and connectors in your boat, make sure that you dispose of the old fuel line responsibly. Do not fling it into the ocean or river or dump it into your waste bin as it can be hazardous to small children and other animals. The fuel line still has oil in it, and it is inflammable. You should wrap it inside a plastic bag and then take it to a particular bin called hazardous material bin to dump it there.

You should always wear protective eye, hand and foot gear for safety reasons. Because you are working with the fuel tank and fuel lines, you should also keep a fire extinguisher with you for emergencies. It is also advisable that you work in a well-ventilated area as the fumes from the fuel can make you drowsy pretty quick.
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Boat Fuel Tanks
Fuel System Vacuum Testing
Vacuum testing your boat fuel system, presented by Bill Grannis of Marine Technician Today Magazine. ... read more By Bill Grannis (Marine Technician Today Magazine; Fall 2013)

An adequate supply of gasoline in liquid form is essential for the health and performance of a marine engine. Symptoms of fuel irregularities include vapor lock, surging, or power loss frequently resulting in engine damage. Often a powerhead failure is blamed on the motor manufacturer when the real culprit is detonation from running too lean – not enough fuel delivery. Multiple engine failures are almost always fuel related.

Anything hindering the flow of gasoline overworks the fuel pump and increases fuel-line vacuum as power output increases. Plugged pickup screens, faulty anti-siphon valves, kinked hoses, plugged filters, or selector valve problems are common offenders. The reduced fuel flow makes an engine run lean at high power settings, contributing to detonation and powerhead damage. In addition, elevated vacuum causes gasoline to vapor lock (boil) at lower temperatures.

High vacuum in a fuel line lowers the boiling point of gasoline whose vapor expands many times its liquid volume. The temperature at which this occurs varies with the amount of vacuum and the volatility of the gasoline. On a hot summer day with alcohol enhanced fuels (E-10) combined with some type of fuel restriction, an engine may surge, stall or fail to start as vapor lock occurs.

Inches of mercury (Hg) is the accepted measurement of vacuum. Manufacturers recommend maximum readings for their motors. Johnson-Evinrude specifications say not to exceed 4” Hg at any speed. Yamaha states no more than 4.5” Hg for smaller than 200 hp and 6” Hg for those above. Mercury specifies 2.5” Hg. A healthy fuel system normally indicates about 2.5” to 3.5” Hg at full flow. The anti-siphon valve accounts for about 1.8” Hg and a spin-on fuel filter adds about 0.5” Hg. Fittings and selector valves with small internal passageways and/or convoluted hose routings increase the reading. Every 12” of lift to the motor adds about 0.6” Hg.

Improper clamps, rusty filters and loose fittings may allow air to leak into the fuel system while underway. Fuel pumps mix the air bubbles and fuel into a froth similar to a “head” of beer. Instead of moving a specific volume of liquid gasoline, the pump feeds this aerated fuel to the engine. The foamy concoction causes lean mixtures, rapidly increasing combustion temperatures and the possibility of detonation.

To evaluate the fuel system, obtain a vacuum gauge, fittings, a pipe-T and clear line. A decent vacuum gauge costs around $10–$20 and is available from hardware stores, industrial-supply companies, or online. Inexpensive automotive pressure/vacuum gauges are not recommended and name-brand professional gauges are preferred if you do not want to make your own.

Precise results cannot be achieved if the motor is run on a “flusher”. Warm up the motor first and attach the test assembly to the fuel-pump input fitting. Do not squeeze the primer bulb as the resulting pressure may damage the vacuum gauge. Have a qualified driver operate the boat in a safe and calm area. Run at all speeds allowing the fuel flow to stabilize first as you monitor the gauge and watch for air bubbles.

Occasional bubbles may be from fuel sloshing but a steady stream is cause for concern. Long sausage-shaped bubbles may indicate a restriction or the onset of vapor-lock. Tighten hose clamps, check threaded fittings, and secure the spin-on fuel filter element. As a fuel-line ages, it loses pliability and may allow air leakage under clamps. Do not overlook primer bulbs, engine-mounted filters, cracked gas-tank pickup tubes, or quick-release fuel-connectors as problem areas.

High vacuum readings are relatively easy to find and correct. A visual inspection of the fuel system may reveal a kinked hose or a fuel-selector valve not fully open. If a filter has not been changed recently, it should be replaced. A defective anti-siphon valve is common and do not overlook the possibility of debris in the pickup tube elbow or screen. Fittings and fuel-selector valves that have small passageways restrict the flow at high rpms. Any internal passageway size should be 1/4” minimum. Use a drillbit shank to check the inner diameter.

To narrow down a problem, unhook the gauge from the motor and connect it to the fuel-tank pickup. This quickly determines if the tank or the plumbing is at fault. Fasten the tester to each connection in turn to discover which component is suspect. Should the tank be questionable, remove the pickup inspect for cracks or trash, and test the anti-siphon valve. A plugged fuel-tank vent (or kinked vent hose) causes a steadily increasing vacuum as the motor is operated. Loosen the gas-cap to see if the vacuum returns to normal.

Sometimes the fuel has to be at a specific level or the boat at a certain trim angle before a problem manifests itself. A label or foil cap-seal often floats around and occasionally blocks the fuel pickup tube. For drivability issues such as surging or stalling, also fasten a pressure gauge on the fuel-pump outlet to determine if the pressure is within spec.
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NAME: Fuel Vents & Fuel System Accessories
Boat Fuel Systems Additives
System Servicing
Servicing your fuel system, presented by Bill Grannis of Marine Technician Today Magazine. ... read more

Tips and Tricks for Servicing Gas Systems

By Bill Grannis (Marine Technician Today Magazine; Winter 2014)

Gas problems are probably the most common causes of engine issues with today’s motors, both inboard and outboard. Ethanol laced gasoline (E 10) deteriorates quickly forming deposits plus absorbs moisture which then settles in the bottom of the gas tank and other gas components. This moisture and alcohol mixture (phase separation) is more corrosive than ethanol by itself and that is what causes the damage to the rubber hoses and the metal parts.

First of all safety is paramount. Always work in a well-ventilated place with no open flames or smoking materials in the vicinity. Use common sense around gasoline or other flammable products and wear eye protection as you never know what may happen. To do the job correctly, always refer to the proper service manual and to latest service literature.

Due to Environmental Protection Agency (EPA) and California Air Resources Board (CARB) emission regulations, many 2-storke outboardswith carburetors or fuel-injection are discontinued. However carbureted outboards outnumber all others by a wide margin and keeping these motors running requires an adequate flow of gasoline and lubricant. Fuel injection is common on 4-strokes which require more involved cleaning if the system becomes contaminated with deposits or debris. The injectors are easily restricted by stale gas, particles from electric gas pumps or corroding metals or damaged gas lines. The old saying “Cleanliness is next to Godliness,” applies to gas components as well as to human beings.

Outboard manufacturers and aftermarket suppliers promote additives that claim to magically clean fuel systems. Most contain alcohols to absorb water in the gas and their cleansing ingredients are not often successful in removing stale gas residue. They are not effective against plugged jets or varnish deposits; that requires disassembly and individual cleaning to do the job properly. Just removing the jets and spraying them with a solvent is not a recommended practice. The internal passageways, emulsion tubes, and calibration orifices need to be free and clear also.

Some shops use the automotive dip bucket and others have good luck with ultra-sonic cleaners with various solutions. In extreme cases you may need both items for hard to clean parts. 4-stroke carburetors may have very small passageways that are next to impossible to clean out if seriously varnished up. Aluminum parts corroded from phase-separated ethanol mixtures need replacement due to pitting and the loss of the protective anodizing.

It is best to have commonly needed parts on hand such as ty-raps, gaskets, and o-rings as those items should always be replaced. Use quality tools in good condition and of course, the proper ones for the job at hand. For example, the 60° Johnson and Evinrude V-4 and V-6 carburetors use special Pozidriv (often misspelled Pozidrive) screws that are easily mistaken for common Phillips screws.

Any screwdrivers with worn, chipped, or rounded blades should be demoted to opening paint cans. For carburetor work a cabinet screwdriver is invaluable. It has about the same blade width as the diameter of its shank and fits into blind holes for jet or screw removal because a traditional slotted screwdriver is much wider behind the tip.

Everyone has had at least one of those “ Oh $#!& “ moments when a tiny fastener or carb part rolls off the bench and disappears in the floor. To minimize any aggravating occurrences common kitchen items may be of assistance. Use a cookie sheet pan with raised sides to contain any small parts and to catch liquids that could spill from a carburetor or a vapor separator tank (VST) during disassembly.

Putting things back together is no fun if you do not have the parts organized at hand meaning that you waste time trying to figure out which item goes where. An ordinary muffin tin with its dozen holes makes for a great organizational device. Each cavity holds different items so they are kept together for quick access such as screws, carb jets, pump diaphragms, check balls, etc. Scope out the thrift stores and yard sales for muffin tins and cookie sheets. Your wife discovering that her kitchen utensils are stained with gasoline and grease will decrease any likelihood of marital bliss!

By incorporating these hints into your servicing procedures, system repairs become less time consuming with a greater chance of being done correctly the first time.
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