As with FSMike, I also read a very scientific type article - there was an argument on this subject at my sailing club and since there are Boeing engineers everywhere someone researched it. The conclusion is that people are taught to put the engine in reverse to stop the spinning b/c the noise
bugs the crap out of people. There should be less drag if it is spinning. But it seems drag isn't the only issue (unless you are a Boeing engineer).
4-108 spins no matter what while under sail - forward, reverse, neutral - doesn't matter if I am sailing fast enough. However, I haven't yet tried switching to reverse when I hear it stop after I slow down...I will try this. According to my crusty 40+ year old Perkins
manual it depends on the type of gearbox
with some being fine to freewheel for 12 hours before needing to run the engine to lubricate the gearbox
, some ok up to 8 as long as shaft speed doesn't exceed certain limits, and some (reduction gear) needs to be stopped to prevent continuous freewheeling b/c the engine isn't driving the oil
pump in the gearbox, and some can be trailed for any length of time provided your gearbox oil
is full. My Challenger 32 manual says I need to run the engine for 15 minutes every 6 hours I'm under sail alone.