DIY Network

Outboard Engine Tune-up: Replacing Spark Plugs From "Shipshape Boating" episode DSSB-101

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The host of Shipshape Boating, John Greviskis, will show you how to do an outboard engine tune-up in this debut episode. Figure A Figure B Figure C Figure D Figure E Figure F

Once your boat's engine hits the 100-hour mark, it's time to replace the spark plugs, and after that the plugs simply need to be checked once a year and replaced only on a need-be basis.



Safety Tip: Always disconnect the engine from the battery before changing spark plugs.

1. Once the engine's power source has been disconnected from the battery, remove the spark plug wires (figure A). For this particular engine there is a bank of three spark plugs, which are exposed once you remove the wires. Remember that every engine is a little different.
   
   
   
   
2. Use a spark plug deep-well socket (figure B) to remove the spark plugs. The insert on the inside of a deep-well socket is rubber, which protects the ceramic portion of the spark plug. Simply slide the socket over the old spark plug and with the use of a drive, back it out (figure C).
   
   
   
   Spark Plug Components:
   • Electrode -- The tip that comes right off the base.

   • Ground Strap -- The black curved tip (figure D) of the plug. You need to make sure that the distance between the ground strap and the electrode is what the manufacturer is recommending. For this particular model, the gap needs to be 1/35,000th, and this can be checked by using a feeler gauge or gapper (figure E). Simply slide the ground strap along the gauge or gapper until you come to the proper setting. The feeler gauge or gapper actually opens the ground strap up as it slides along.

     Note: If the ground strap opening is either too large or too small, it can result in a problem called "pre-ignition" where the spark plug will wear out too quickly.

3. 
   
   
   
4. Once the ground strap has the proper opening, it's time to attach the spark plug, using a spark plug wrench. Make sure to align the wrench over top of the spark plug (figure F) and then tighten.
   
   
   
   
5. Once the spark plug is secure, it's time to attach the proper spark plug wire. On this particular model, the top wire goes to the top plug, the middle wire to the middle plug and the bottom wire to the bottom plug with this three-tier structure.

RESOURCES :
Troubleshooting Gasoline Marine Engines
Model: 1892216280
Author: John Fleming
(January 2001)

To order this title from Amazon, click here.

Bristol Fashion Publications

Boat Engines: A Motor Boat and Yachting Book
Model: 1898660042
Author: Dick Hewitt
Order this book from Amazon.com.
Fernhurst Books

Boat Repair Made Easy -- Engines -- Diesel and Gasoline ...
Model: 1892216035
Author: John P. Kaufman
Order this book from Amazon.com.
Bristol Fashion Publications

Outboard Motor Engines: Maintenance, Troubleshooting and Repair
Model: 0070578567
Author: Edwin R. Sherman
(April 1997)

To order this title from Amazon, click here.

Ragged Mountain Press
Camden, ME 04843-0220
Phone: 207-236-4837
Fax: 207-236-6314

Outboard Motor Service Manual
Model: 0872884643
Author: Intertec

To order this title from Amazon, click here.

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