T&T: prop shaft lock

[JHWardJr at aol.com]

"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
 
 







**************Wondering what's for Dinner Tonight? Get new twists on family 
favorites at AOL Food.      
(http://food.aol.com/dinner-tonight?NCID=aolfod00030000000001)