KAMD 42A Cruise RPM

[Battledeck]

Hi
I have a 30 ft Blackwatch in Australia with twin KAMD 42A 230hp.
I achieve 3900 RPM WOT, what would be the optimum cruise RPM?
I am thinking 3200 for the best speed, ecomomy and longevity.

Also any fuel usage figures would be great?

Thanks Stephen

 

[Greg2]

I can only say what we experienced with our Fairline Targa 35 with twin KAD 42's - same engines but on outdrives.

At WOT they pulled around 3800 rpm, which is what the book says it should be. We used to cruise at around 3000 rpm (min 2800 and max 3200) which gave us around 22 to 25 knots depending on conditions. Actually we were atv3000 rpm most of the time.

I guess hull design etc will influence what is right for each boat.

Hope this helps.