Boating Tips


Posted 8/20/2010

The illustration above depicts basic outboard fuel system components.  Fuel system fuel and vent hose access.  Fuel sending unit access.

Fuel system troubles are, for the most part, preventable if you pay close attention to the details. Regular fuel system maintenance isn't difficult, doesn't require a lot of time or special skills – it's simply a matter of following the instructions in your engine and boat owner's manuals and applying a little common sense in the process.

The Fuel System
A basic marine fuel system (for boats powered by gasoline internal combustion engines) consists of:
• The fuel tank (permanent or portable)
• A fuel sending unit (electrical sensor on permanent tanks that sends fuel level to gas gauge)
• The fuel deck fill (or cap on portable tanks)
• The fuel fill hose (from deck fill to permanent fuel tank)
• A fuel tank vent (small fitting connected to gas tank via a hose or screw-on cap on portable tanks)
• Fuel line(s) (from gas tank to engine)
• Fuel filters (between gas tank and engine, engine mounted)
• Oil tank (oil injected two-stroke outboards)

Common Fuel System 
Issues and Potential Fixes

• Little or no fuel in the gas tank (gas gauges can lie)
• Pinched or kinked fuel line

Potential Fixes: 
• Put plenty of gas in the tank
• Check fuel lines for smooth routing


• Inaccurate Gas Gauge

Potential Fixes: 
• Check electrical connections at fuel sending unit on gas tank
• Check electrical connections at gas gauge
• Test gas gauge (if possible)
• Fails test, replace gauge
• Test fuel sending unit
• Fails test, replace fuel sending unit

• Poor Fuel Quality
o Lower octane rating than specified on the pump 
o Fuel degradation/old, stale fuel
o Water in the fuel
o Debris in the fuel system (clogs filters, obstructs fuel flow in carburetors and fuel injectors)
o Ethanol-related issues (too much water in gas tank – phase separation, fiberglass/plastic gas tank damage, fuel line deterioration, etc.)

Potential Fixes: 
• Drain the fuel tank
• Replace all fuel filters (in the boat and on the engine)
• Refill tank with known good gas and add the appropriate amount of a high quality, marine grade fuel stabilizer
• Use up the first fresh tank of gas and replace all the fuel filters again (to ensure all water/debris is out of the fuel system)

• Fuel Leaks
o Fuel lines, especially at quick-disconnect fittings, primer bulb, and anywhere there is a fuel line connection

Potential Fixes: 
• Inspect for cracked fuel lines (on boat and engine)
• Inspect primer bulb for cracks and tight connections
• Tighten hose clamps (on boat and engine)

WARNING: Gasoline and its vapors are highly flammable and explosive. Keep away from sparks, cigarettes, flames or other sources of ignition. Please review your specific Owners Manual for complete details and any related Warnings.

Prevention is the Cure
We consulted with the experts at Yamaha Marine; they recommended these easy and inexpensive preventive maintenance tips:

Install the Finest Fuel Filters You Can Buy 
• Yamaha 10-micron inline filters remove an unbelievable amount of water and debris from gasoline
• Fuel filters from the engine manufacturer are probably the best for engine-mounted filters

Use name-brand fuel additives at each fill-up to prolong the life of the fuel and engine
• Yamaha Fuel Conditioner and Stabilizer PLUS 
o Helps protect the fuel system and engine from ethanol-related issues 
o Prevents fuel deterioration
• Yamaha Ring Free PLUS
o Helps eliminate harmful carbon build-up in outboards

Use high-quality fuel from a reputable source
• Preferably from a place that sells a lot of fuel – the fuel is more likely to be fresh

Visually inspect the fuel system several times during the season 
• You might find a problem waiting to happen.

In addition, be proactive and follow each simple step of the fuel system maintenance procedures regularly as outlined in the engine and boat owner's manuals' maintenance schedules.

Finally, take the boat out on the water to use the fuel before the gas has a chance to get stale or absorb water. Yes, we know it's a real hardship, but you need to go boating more often than you usually do – consider it a cardio workout for your boat and engine.