Q & A — June 2002
By Capt. Ken Kreisler
The proper way to clean a flame arrestor, testing a thermostat out of an engine, and more.
is the proper method for cleaning a flame arrestor? I.J., via e-mail
While you should always follow your owner's manual for proper flame arrestor removal and cleaning, most units are serviced in the same manner. First disconnect the crankcase vent hose. (Depending on your engine size, there may be more than one hose.) Remove the nut holding the flame arrestor and cover. On some engines, like older Volvo Penta stern drives, a clamp may secure the flame arrestor to the air intake horn. With them you will have to also loosen the clamp.
Remove the cover, flame arrestor screen, and gasket if one is used. Inspect the air inlet screen, and if it is damaged or deformed, replace it. Submerge the flame arrestor in a container of clean solvent. (Many can do the job, but you'll always be safe in selecting one recommended by your engine manufacturer.) Let it soak long enough that any residue is loosened, after which you can slosh the solvent around for a few seconds to remove the particles. Once it looks clean, let the flame arrestor sit in the solvent again for a few minutes.
Remove the flame arrestor from the solvent, and let it drain. You can blow it dry with compressed or canned air to speed things up. Once the flame arrestor is dry, you can put it all back together. If the unit has a gasket, replace it with a new one.
there a way to test a thermostat out of the engine? N. R..
Pour some tap water into a shallow container that can be heated. Place your thermostat in the water, and suspend a thermometer in it so you can read the temperature as the water is heated. Heat the water until the thermostat starts to open while checking the water temperature on the thermometer. This should coincide with the temperature value stamped on the thermostat. If it has not started to open at this temperature, replace the thermostat.
If it begins to open when it should, continue heating the water another 25°F above the stamped temperature value, at which point it should be fully open. If it is not, replace it. Now, allow the water to cool to 10°F below the rated value. If the thermostat is not fully closed at this point, you must replace it.
As a thermostat is inexpensive, keep a spare or two onboard just in case you have to do a quick switch.
This article originally appeared in the January 2003 issue of Power & Motoryacht magazine.