We have a 30U w/ the venerable WB27 and a 2 blade folding prop. At 2000 rpm we manage 6kts unless we’re bucking heavy seas. I hear other 30U owners speak of faster motoring speeds 7-8kts under power, and they have the same engine prop setup that we do. We never exceed 2000 rpm per the advice of the previous owner, and am wondering what other owners’ experiences have been.
Welcome Matt - I also have an elderly W27 with the stock two-blade prop, we usually run closer to 2500 rpm and I’m happy if I’m getting 6kts average and burning about 1/2 gallon of diesel an hour - I think the max is closer to 3k and diesels like to be run open (less varnishing, cleaner burn etc.)
Before Joe weighs in about your signature, everyone on here uses the following convention:
Jim Denmark
C.A.T. 1982 Nonsuch 30C #146 lying on the hard, Oriental, NC
Check the owners guide for the max rpm speed and cruise at 75 - 80% of that speed. Your engine will love you. T.he attached document shows 3000 at the max hp rpm so 80% of that. About a knot under hull speed is usually as good as it gets for motoring
(attachments)
w27.pdf (1.99 MB)
Not knowing who or what you are, I just want to mention that in flat seas, with the same setup, I will do 6.5 kts at 2800 with a Gori 2 blade. I would disagree with the 2000 RPM number. When pressed, I will run at 3200 to make a bridge or outrun a thunderstorm.
Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA
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I reach hull speed about 2200 revs, if I take her all the way to 3000 I am pushing a bow wave like a liner… however I have a 30 ultra, VC-17 bottom, 33hp wb and a matched Campbell prop.
Works for me…
Brian McCuaig. NS30u
Whitby, Ontario
“Having a Nonsuch is reason for being more cheerful than most."
I have a W33 as well with affixed two blade prop. I hit hull speed at just over 3000. This is a 3600 rpm engine. If you get hull speed at just over half that rpm I would suggest that your prop is not well matched. I cruise at a knot under hull speed (~6 1/4) @ ~ 2700. I think this is where a well matched prop should put you. It is right in the fuel efficiency / torque sweet spot.
Paul M
NS30U #211, Sandpiper
Cowichan Bay,B.C.