Diesel Fuel consumption

[gcampbell]

Gentlemen: I have heard a rumor that long range offshore fishermen (maybe commercial) in the northeast US are using an odd drive configuration with IB diesel power and extra large props. Any info on the subject? Somehow they are getting great fuel milage. Thanks in advance.

[marshmat]

IB diesel power and huge props would indeed imply very good fuel efficiency. I haven't seen the system you seem to be talking about though, I'll see what I can find.

[gcampbell]

Thanks for the reply Marshmat. I believe the basic idea is to use 3:1 or 4:1 transmissions and larger props with a lot of bite.... general parameters show 40ft boats gaining 7-8 kts and showing a small decrease in fuel consumption

[Deering]

Bigger props are almost always more efficient, but usually limited by clearance space between prop shaft and hull. How are they getting around that limitation?

[gcampbell]

Thanks for the reply Deerling, I dont have that info.... its all part of the info I am looking for. For myself, I will form a concave section into the hull if I need to.... but that is a much larger discussion for a later day. GC

[FAST FRED]

Simplest method of reducing fuel consumption is to use a prop with fewer blades. As long as the blade area were enough , and the diameter wouldnt cause grounding problems a 2 blade would be best.

There were single blade props made for aircraft , but the dia would be huge for a boat.

FAST FRED