On Fri, 28 Sep 2007 13:23:53 -0700, Diego wrote:

I have a boat with twin 350 hp Crusader gas engines. I would like to
cruise this boat between Florida and the Bahamas. It will be optimal
for me to cross the Gulf Stream at high cruising speeds to get out of
harms way, then reduce to a very slow speed when moving around the
islands in order to conserve fuel and increase my range. I've heard
that this can cause fouling of spark plugs. Has anyone tried this and
can comment on doing something like this? Does the plug fouling
happen over a lengthy period of time (weeks) or rather quickly (hours)?

In autos, spark plugs now generally last 100 000 miles. They have
platinum electrodes that can run hotter and still last. Do you have an
ignition system anything close to a high performance, i.e. electronic,
or magneto? In cars plug fouling is pretty much a thing of the past.
There used to be a problem with lead fouling, but lead is pretty much
gone. You can still get 115 octane, called LL100, aviation fuel with
lead in it. Some use it in race cars, and I think, go fast 90 MPH type
boats. I had platinum plugs in an airplane in the sixties. Lasted 1000
hours,and still looked good. The steel ones lasted 25. A guy
overhauled his motor at 1000 hours. The platinum points were good, but
he replaced them anyway, and gave me the old ones. They cost about $25
v.
$5 or so for steel. Made a believer of me, and a few years later, they
started making them for cars. In some ways, the good old days,
weren't.
I don't guarantee you can't get fouling with platinum plugs, but it is
the way to go.

Casady