BoatUS Cruising - Tom Neale's Cruising For You: Tom's Tips - Outboards


  • The dead man’s switch generally works by connecting the ignition circuitry to ground, thereby depriving the spark plug of the “spark.” When the little tab on the end of the red cord isn’t in place on the switch, the switch is on, closing contact internally, and establishing the ground connection. Often these switches become corroded and short out inside or become stuck in the on position. This may prevent the motor from starting even though you’ve inserted the tab. Although you should replace the switch as soon as possible (these switches are very important for your safety), you can make an emergency get home repair by simply disconnecting or cutting the wire running from the switch to the electrical component.

  • In the good ol’ days, outboards had shear pins which would break when the propeller hit something. This protected the shaft and gears, and you could easily replace a broken pin in just a few minutes. A handful of pins cost a few dollars. Now, most manufacturers have done us the favor of using a rubber insert in the outboard propeller, instead of a shear pin. It binds the outer ring, to which the blades are attached, to the hub. When you hit something the rubber tears. They say that this is better because of the shock absorbing function of the insert, and because, unless you really cream your prop, there will be enough friction between the torn rubber surfaces for you to get home---just very very slowly. Never mind that when this happens you have to buy a whole new prop instead of just a pin.

    If I’m going to do something, I like to do it well. This applies to hitting the bottom and other things with my prop. When this happens, you’re not going anywhere, unless you have a spare prop to put on. BUT, in most cases you can make a temporary get-home repair to beef up the torn slipping insert. Screw at least 3 screws into the insert, about half way between the inner and outer edges. Flat nails will also work. The thickness of the screws or nails will depend upon the thickness of the rubber insert. This will hopefully expand the rubber and usually cause enough friction to decrease the slippage and allow you to get in.

  • One of the first steps in making a diagnosis should your outboard crank but not start, is to pull the plugs and look at the tips to see if they’re wet with gas and/or oil. If they are you probably don’t have a spark, or there’s so much gas that it’s flooded. Dry them off and let the engine sit a few minutes before reinstalling them, and try again. If they’re still wet without starting, you’re probably not getting the spark. If they’re dry, the problem may be with your carburetor. If the plugs are greasy with a lot of oil, you may have too much oil mixed in your gas.

  • Sometimes you’ll see mechanics look for a spark by removing the plug from the block, leaving the wire on, grounding the base of the plug against the block, cranking the motor, and checking for the flash at the electrode. If you do this in bright sunlight, you might not see the spark unless there is a dark background. Often you have to put your face close to the plug to see the spark. This can be a dangerous operation because it could cause an explosion by igniting gas vapor coming from the spark plug hole in the block. You’ll also feel a shock if you hold the plug without insulation protection.

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Go to for more tips about outboards and other subjects.

Copyright 2004-2010 Tom Neale

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