Myth vs. Reality

Posted: September 1, 2012

Your Dinghy’s Outboard

By: Matt Gurnsey

Technology changes, innovation presses on and advancements are made. Eventually the-way-we’ve-always-done-it becomes antiquated, replaced by new ways, new recommendations and new rules. During times of change, confusion creates misunderstanding and misinformation. Myths somehow become common knowledge — even when the common knowledge is wrong. Here are some myths surrounding the outboard motor that may be sitting on your dinghy, as well as the reality behind them.

Myth: More horsepower always means more speed.

Reality: Sometimes more power just means more expense and wasted fuel. Soft-bottom dinghies often don’t have the rigidity to benefit from more power, plowing through the water instead of lifting (and getting everybody wet). Often, more power means more weight. The move from 20 hp to 25 hp often adds 40 pounds in engine weight. Increasing from 30 hp to 40 hp can be 60 pounds of added weight. Older boats designed for lighter-weight, old-technology two-stroke power may not run well with extra weight on the transom.


Myth: Motor oil is motor oil.

Reality: Marine four-stroke engine oil is formulated with different additives than automotive oil. These additives help prevent corrosion on cylinder walls and other internal components. Just as automotive oils have letter designations or ratings, so does oil for four-stroke outboards. Either use the same brand oil as your outboard or look for the FC-W rating, to be sure the oil you use is rated for marine use.


Myth: Fuel stabilizer is just for winter.

Reality: Fuel has changed. Gasoline formulations have changed, and the introduction of ethanol has been causing problems with fuel breakdown and damage to fuel-system components. Using a stabilizer designed for ethanol fuel will help prevent fuel breakdown and protect expensive fuel-delivery systems. Most stabilizers are used at lower concentration for normal use, with stronger mixes used for winterization. Local mechanics will be able to advise what products work best in your area.


Myth: Always run your outboard motor out of fuel.

Reality: This is good advice for carbureted engines but bad advice for fuel-injected motors. Repeatedly running fuel-injected motors out of fuel can damage the internal components of the fuel-delivery system. Since these are sealed systems, it is better to have stabilized fuel in the system for lubrication and cooling of the fuel pumps.


Myth: Four-stroke motors can idle all day long.

Reality: While four-strokes idle smoothly, too much low-speed operation can be harmful, especially during break-in. Improper break-in can result in rings that do not get set properly and glazed cylinder walls, resulting in fuel blow-by past the rings. This fuel then dilutes the oil, eventually causing engine damage. Make sure that engine operation includes a mixture of speeds from idle to wide open to extend engine life.


Myth: Hydrofoil stabilizers are snake oil.

Reality: Some say that if the enlargement of the cavitation plate was such a good idea, the manufacturers would build the motors with them. But some boats do benefit from the additional lift aft. Especially when a heavier engine is installed. The extra lift may help get the extra horsepower of a heavier engine moving the boat forward. Four-stroke engines can have less torque than their two-stroke counterparts, and the extra lift can make the difference between getting the boat on plane, or not.

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