repower with Cummins 6B NA or 4BT Turbo 4

[powerabout]

Guys

I am looking at repowering a 42 trawler that has 120 Lehmans.
I would prefer to use Cummins but I can choose 6B or the 4BT, either would have ok power.
What will the cruise fuel economy look like with;
a) either 6 or turbo 4?
b) on one engine with the other windmilling.
c) what does the engines power curve versus the prop curve look like when comparing the 2 for a displacement boat?

Thanks in advance

Powerabout

[charmc]

Some Cummins fuel consumption data here (page 7):

http://www.cmdmarine.com/PDFs/4081938_1104.pdf

At 130 vs 120 HP, the 4BT seems to have an slight edge in fuel consumption. In the boat, that edge should increase, as it also has a 200kg weight advantage.

For the rest, find the Cummins Marine distributor for your area; they should have access to that data.

[charmc]

http://distribution.cummins.com/wps/...7&childId=1963

[lazeyjack]

u used to work for cimmins years ago, I also used the 4b a lot is sailing yachts
I would use the John Deere teir 11, 4.5
Why
cos it a wet linered engine, seize a piston and its easy fix one piston one liner
same as big engines
The 6b engines are fine engines dont get me wrong, but the Deere has(here) a very significant price anvantage The Deere is happy to run at 1400 , or 1200 all day, or 2600, there are three ratings 1,2,3, 120 --135 bhp depending upon hours per year