Can my outboard be damaged if its relief port becomes submerged?
M.J., via e-mail
Yes. The most common result of a clogged relief port is “coking,”
the buildup of carbon deposits. This can lead to knocking, pre-ignition,
and poor fuel and oil management. Left unchecked, these problems could
lead to piston damage and engine failure. A discussion of what happens
to exhaust gases during outboard engine operation may help explain why.
All cylinders dump exhaust into a common manifold where water is introduced
to cool and muffle it. The exhaust-water mixture then passes down a passage
in the drive unit and eventually exits through the propeller hub. When
a boat is at idle or slow speeds, however, the static water around the
prop produces too much resistance to the exhaust, resulting in excessive
backpressure. (When the boat is moving, a low-pressure area behind the
propeller prevents this.) To alleviate this problem, one or more passages
are cast or machined into the intermediate housing just above the waterline.
If pressure builds at the prop, the exhaust can escape through these ports.
If these ports are restricted—say, by overloading the boat to the
point where they are submerged—exhaust won’t escape, cylinder
temperatures and pressure will rise, and deposits will form.
I tried to fix a small hole in my inflatable
but found that the patch would not hold, even when I tried several different
glues. What could be wrong? B.F.L., via e-mail
You probably used a silicone-based compound like Armor-All to clean your
inflatable. The chemicals in it infused the fabric and the glue therefore
could not adhere to it.
To correct this problem, you’ll need to clean the area with a strong
solvent and may have to sand it as well to ensure a good bond. Contact
your boat’s manufacturer for solvent recommendations. How can I remove
masking tape from stainless steel fittings? H.R., via e-mail Lacquer thinner
or nail-polish remover will do the job. Brush the liquid on so that it
coats the tape. Let it soften for a while. You should then be able to
carefully peel off the tape. If any adhesive remains, rub the area vigorously
with a thinner-damped rag. Use lacquer thinner and nail-polish remover
with caution, as both will attack varnish, paint, and many sealants.
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: email@example.com.
No phone calls, please.
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