Q & A — August 2001
By Capt. Ken Kreisler
|Piston damage, preventing mineral deposits, and more.|
I’m preparing to bond some hardware to the deck. To what consistency should I mix my filler material? H.C., via e-mail
For this application the filler should be thickened to the consistency of mayonnaise. If it’s right it should cling to a vertical surface, and when you quickly dip a mixing stick into it, it should form peaks.
Mix your filler in small batches, and always mix the resin and hardener thoroughly before introducing the filler. Add filler in small amounts until you reach the desired consistency.
I’m an out-of-the-book mechanic, and when one of my 200-hp outboards lost power and would not restart, I later discovered that the tops of the pistons were severely damaged. What caused this, and how can it be avoided? L.G., via e-mail
The cause was probably detonation, which can have many sources but is usually due to carbon buildup on the piston crown. This increases the compression ratio and causes "knock." Carbon also retains heat and in fact can get so hot it ignites the fuel charge before the spark plug–usually while the piston is still on the up-stroke. The result is a collision between the expanding gases and the rising piston, which can easily damage the piston crown. If it’s severe enough, the explosion can actually blow a hole through the piston crown.
Carbon buildup can be caused by using the wrong two-cycle oil or poor-quality gasoline or by an engine running too cold. Other causes of knock include improper ignition timing, improper spark plugs, too lean a fuel mixture, overheating, overloading due to use of an incorrect prop, and excessive exhaust back pressure.
The most important preventive maintenance measure is using the right two-cycle-rated oil, as recommended by your engine manufacturer in your owner’s manual.
How can I prevent mineral deposits from forming in my boat’s shower head, and restricting the flow of water? F.E., via e-mail
The mineral deposits are coming from "hard" water, water with a high pH. To eliminate them you’ll have to "soften" the water and lower the pH.
The best way to do this is by installing a filter-type cartridge designed for this purpose in your water system. Any of the popular brands on the market today will take care of the problem. Then it’s just a matter of changing the filter at the recommended times.
In the meantime you can remove the residue by spraying the showerhead with Tilex and scrubbing it with an old toothbrush. If the buildup is particularly heavy, remove the showerhead and give it a thorough cleaning inside and out with Tilex.
If you have a chrome showerhead, try soaking it overnight in vinegar. Don’t use vinegar on solid brass or brass-plated fixtures, as it will damage the finish.
Need help with a maintenance problem? Write to Maintenance Q & A, Power & Motoryacht, 260 Madison Ave., 8th Fl., New York, NY 10016. Fax: (917) 256-2282. e-mail: firstname.lastname@example.org. No phone calls, please.
This article originally appeared in the June 2003 issue of Power & Motoryacht magazine.