More of this Feature • The Basics • The Basics continued • Stern Drives • Outboards, Gas Inboards, Diesels
Related Resources • Maintenance Index

Outboard Motors
• Replace spark plugs.
• Check external gasoline tanks for corrosion, and replace if necessary. Look for cracks in the priming bulb, and test it for firmness and resiliency. If it collapses, replace it.
• Note the color of the lube oil in the lower unit. If it’s cloudy, there’s probably a leak around the prop-shaft seal. Fix it and change the oil.
• Look for leaks around the trim cylinders.

Gasoline Inboards
• Replace spark plugs.
• Clean flame arrestor.

Diesel Engines
• Clean air filter, if installed.
• Once you’re up and running and the engine is under load, note the color of the exhaust. This can tell you what is going on inside your engine. Black exhaust indicates either too much fuel or not enough air or an unsuitable prop. Check for a clogged air intake or improperly adjusted fuel system. Blue smoke indicates that oil is burning in the combustion chamber. Possible causes could be worn piston rings or cylinder walls, worn valve guides, or a clogged crankcase ventilator. Refer to your engine log and note last year’s oil consumption. If it gradually increased over the year, do a compression test on each cylinder before calling in a mechanic.
• If your oil filters are spin-on units, apply a thin film of oil to the gasket and hand-tighten when replacing. If the filter is a cartridge, make sure the O-ring gasket is properly seated before reinstalling. Filters should be topped off with clean oil before starting your engine.

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