Mr. Catfish wrote:

During adverse conditions, 45knt gusts, blinding rain a tide going out and a
current besides, (At one point I looked at the GPS and with the engine
running 2400rpm we were going 0 knts) shortly after this the engine
overheated so I shut it off, there was enough sail sticking up so I had
steerage but I did get blown off course. After about half-hour of being
blown around I started the engine, the temperature came down to normal
slowly and the engine ran fine for the next few hours it took to get back to
the slip. Is this engine getting too old (1979) ? Thermostat and impeller
about 20hrs., raw water cooling, strainer not clogged, no air leak.
Do the water passages get clogged after years of use and if the engine is
under strain it will show up as overheating?


The other comments are useful, particularly cleaning out the raw water
cooling passages, but 2400 RPM seems VERY low revs for what I expect
would be high-cruise (or higher) engine settings. As I recall, the older
Yanmars had a 3200-3600 max range like the newer ones such as ours
(2GM20F). In other words, this sounds like an over-propped engine which
would overheat at relatively low power settings.

We propped for our 1-hour max setting. True to specs, the engine
overheated about an hour after we firewalled it. (that hour got us
nearly a quarter nm further, though we had to drop revs drastically for
a few minutes to let the cooling system catch up.) When running at the
continuous setting (200 RPM lower), we cruise for as long as we want --
at very high consumption rates.

We now cruise at 2200-2400 normally, which gives us about 80% of hull
speed in flatish water. If we're rushed, like a couple of weeks ago, I
can bring the boat's speed up high enough to maintain surfing conditions
much of the time in downwind conditions and can punch through waves when
we're going upwind at nearly hull speed (though at an angle, not head-on
with our blunt bow section).

If we pitched a bit more aggressively, we could cruise faster at lower
RPMs, but couldn't go as fast when we really needed it.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/