Just reviewing my notes from yesterday's sea trial of a 37-foot
semi-displacement trawler.

425 HP Cummins QSB engine.

That's not a bad engine choice for a single screw boat- it can be
operated at a low rpm without loading up (thanks to computerized fuel
control), and it can ber pushed pretty hard to get more speed than one
might otherwise expect from a boat in tht category.

Fuel consumption figures are taken from the engine-diagnostics screen
installed with the Cummins QSB.

Traditonal trawler fans will recognize the performance figures at 1400
RPM, 8.2 kt at 2.4gph.
On the other end of the performance spectrum, WOT is 3000 RPM where the
boat makes 16.5 kt at 22.4 gph.

Makes a dramatic statement about fuel economy: Doubling "displacement"
speed in this boat
uses almost exactly ten times as much fuel.

"Chuck Gould" wrote in
ups.com:

Traditonal trawler fans will recognize the performance figures at 1400
RPM, 8.2 kt at 2.4gph.


http://www.perkins-sabre.com/PR/Engi.../Equipment.cfm
8 knots on half that fuel. The Perkins will be running after he's dead.

Larry wrote:


http://www.perkins-sabre.com/PR/Engi.../Equipment.cfm
8 knots on half that fuel. The Perkins will be running after he's dead.

I own a late model Perkins engine. 6354 NA, 130 HP. Like it a lot.

I would doubt that the 4 banger you link to (86 HP at 2400 RPM) would
be an ideal choice for a 24,500 pound boat that one wanted to cruise at
8 kts. Nor am I inclined to believe that wound up to 2400 RPM (where
you *might* have a chance to get 8 kts out of it. maybe.) fuel burn
would be down to 1.2 GPH, which is what it would need to be to come in
at half the fuel burn of the QSB I referred to. And lastly, pushing
that 4 cylinder with its shorter crankshaft and less torque hard enough
to do the job would shorten its life expectancy considerably.

My last Perkins racked up almost 4000 hours before it croaked- and even
then it was a manifold failure and not really anything that Perkins did
when building the engine.

It's easy to agree that Perkins builds a very good engine. Older
technology on most of the models- which was one of the reasons I stuck
with Perkins when I had to repower.

There are some Krogens and Norhavns out there with very small single
engine mains, probably for maximum possible range offshore, but slowed
to 6 knots almost any engine is going to get pretty impressive fuel
economy.