CONTESSA 32 ASSOCIATION Homepage
Forum Home Forum Home > Technical Help > Engine, Gearbox, Stern Gear, etc
  New Posts New Posts RSS Feed: Speed & Revs
  FAQ FAQ  Forum Search   Calendar   Register Register  Login Login

Speed & Revs

 Post Reply Post Reply
Author
Message
Speedwell View Drop Down
CO32 Members
CO32 Members


Joined: 02 Nov 2015
Online Status: Offline
Posts: 18
Post Options Post Options   Quote Speedwell Quote  Post ReplyReply Direct Link To This Post Topic: Speed & Revs
    Posted: 07 Oct 2016 at 8:05pm

I am getting about 4.5-5.0KTS from our ~20yo Yanmar 2GM20 and Darglow 3-blade folding prop. The engine appears in good condition and well maintained. We have no rev counter so I estimate what feels right for the engine, but since on one occasion I ended up with a sooty transom I am nervous about over-revving.

What speed should we be getting with this setup and what methods do people use for estimating the correct power settings without a techo?

Many thanks
Back to Top
George Isted View Drop Down
Moderator Group
Moderator Group
Avatar

Joined: 08 May 2009
Location: Solent
Online Status: Offline
Posts: 371
Post Options Post Options   Quote George Isted Quote  Post ReplyReply Direct Link To This Post Posted: 07 Oct 2016 at 8:41pm
4.5-5kts through the water is comfortable on Concerto with exactly the same engine and prop, it's about 2400rpm.   I can get the boat to go faster but it gets loud, produces smoke and burns lots of fuel for a small increase in speed.

With a clean bottom and prop she will do about 6.5kts flat out in flat water but I don't do this as a matter of course.

That said the engine does like to be worked reasonably hard and a decent period of motoring at higher rpm is good for the engine every now and again.  It clears out carbon deposits and mine always runs sweetly after.

If you want a cheap tacho take a look at the tinytach  http://www.tinytachuk.com/   I don't have one but I'm told they are good.

If you are getting excessive black smoke it could be the prop/hull is grubby or the prop has slightly too-course a pitch.  
George Isted
Contessa 32 "Concerto"
Co32 Class Captain and Measurer.
Back to Top
Speedwell View Drop Down
CO32 Members
CO32 Members


Joined: 02 Nov 2015
Online Status: Offline
Posts: 18
Post Options Post Options   Quote Speedwell Quote  Post ReplyReply Direct Link To This Post Posted: 07 Oct 2016 at 10:05pm
Thanks George. Seems like I'm in the right ballpark. I was expecting 5.5KTS without pushing too hard but we always speed up when the sails are up. 
I'll give the Italian tune-up a go!
Back to Top
 Post Reply Post Reply

Forum Jump Forum Permissions View Drop Down