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wenders

Quote:

Originally Posted by Wayne.B

On Tue, 19 May 2015 05:24:54 +0100, wenders
wrote:

If I shut down one of my engines to save fuel, am I supposed to block
the shaft of the dead engine in order to protect the transmission? And
what is the best way to do this?

===

I've had numerous conversations with my mechanic and others on this
subject. The problem arises because the transmission depends on
circulation of oil for lubrication and cooling. The pump which
creates that circulation is driven by the engine side.

Some say that if you run slowly (under 7 kts or so), that there is
little or no risk. I've done this on numerous occassions without
experiencing any problems, and have observed no abnormal temperatures
as measured by an IR heat gun. Others say that it's OK if you briefly
restart the engine every hour or so to ensure lubrication.

On the other hand both my mechanic and the transmission manufacturer
(Twin Disc) strongly recommend against it, and consequently I have
stopped doing it. The generally accepted method of securing the shaft
from rotation is to chain it down, i.e., wrap the coupler with chain
and fasten it to a strong point on the boat. Obviously this has to be
done with the boat stopped.

There is a secondary issue that you may not be aware of. The shaft
log and/or cutlass bearing frequently rely on a flow of cooling water
from the engine raw water system to prevent wear and over heating. If
the associated engine is shut down, that flow will no longer be
present unless you have installed cross over hoses from the opposite
engine.

Bottom line for me is that the risks out weigh the potential fuel
savings. Rebuilding or replacing a transmission costs many thousands
of dollars plus the inconvenience and down time. Chaining down the
shaft is tricky and has its own risks. A possible alternative is to
leave the engine running at idle speed instead of shutting it down.
Diesel engines do not like to idle for long periods of time however
and will eventually develop carbon deposits and/or stuck rings.

Your point is well taken. I would never try to put the boat on a plane with only one engine. I was more thinking of trolling at low rpm on one engine.
I would still want to block the dead shaft, but still have not quite figured out how. Appreciate your input.