Next message: Roy Holleman: "T&T: Gulfstar"
"what do twin engine boat's do when running on one engine to stop prop shaft
spin on the down engine?"
A little backgound - much shortened:
On my maiden voyage of my twin FL160-powered Present 42 I had a drip leak in
the starboard fuel line. I shut off the fuel at the Racor and ran for 30
minutes or so on one engine with the shaft spinning. Got nervous about
potential damage, so pulled into a fortuitous port and made repairs.
What I discovered was that the boat ran really well on one engine - tracked
straight, helm responsiveness acceptable, quieter, and the running engine was
pulling more power in the meat of it's torque curve. But the windmilling
shaft...
I have since done some research with the Borg Warner Velvet Drive tranny
tech service guys - freewheeling at trawler speeds (under 10 kts) will NOT cause
a problem. The defining issue is that the oil is churning and gets warmed
by the shearing of the oil and low load gear meshing. He said that to feel
better I could monitor the case temperature - if you can hold your hand on it -
you're ok. In my case (not a single being towed and the second engine
usable) - if it gets hot, fire it up every now and then to cool the tranny oil.
Or alternate the engines.
I also asked about potential oil damage. He said if it does not turn black
or rancid - no problem.
BTW - I have never heard a definitive treatise on the drag from a
windmilling vs locked/stopped marine prop. In the aviation world, a windmilling prop
has orders of magnitude more drag than a stopped one (even if not feathered).
My belief is that water props have less drag if spinning (can someone that
really knows weigh in on this?). Obviously the best solution would be to
feather it like some sailboats do. Or take it off.
The towing boys probably know this, but might not answer you for fear of
liability for potential damage during the tow. Also, my comments are for the
Velvet Drive tranny only - I do not know about other designs. Regards, JeemboNC
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