On Wed, 23 Feb 2005 23:51:31 -0500, "Doug Dotson"
dougdotson@NOSPAMcablespeedNOSPAMcom wrote:

"Wayne.B" wrote in message
.. .
On Wed, 23 Feb 2005 20:41:51 -0500, "Doug Dotson"
dougdotson@NOSPAMcablespeedNOSPAMcom wrote:

I run a 1985 Perkins 85 HP 4 cylinder pushing a 43'
boat. I consistantly burn 1 GPH.

==================================

If so, you are only using about 20 hp out of your 85 available. At
85% of full RPMs it should be burning about 3 gph unless you are way
under propped.

Scoots me along at just under hullspeed. Last surveyor said it was
propped just fine.

I do 5.8 knots at 1/2 throttle on a direct drive Atomic 4 with a 12" x
6" "standard" two-blade prop pushing a 10,000 lb boat with a 27' LWL.
Hull speed is just under seven knots. RPM is around 1,500-1,600.

I can get to 6.6 knots SOG at 3/4 throttle, but the noise is
unpleasant and I start burning a lot more gas...it's not worth it.

I can sail in heavy air favourably angled slightly above hull speed
(7.3 knots SOG) for sustained periods, or about 1.5 knots

I have logged a pretty consistent gas usage of 0.73 Imp. gal/hr. which
is about .825 U.S. gal, I think. That's at a typical cruise speed of
1/3 throttle or 5 to 5.2 knots. A 12 gallon tank gives me a range of
about 84-90 NM or just under two round trip Toronto-Niagara River
crossings. Motorsailing increases this significantly, of course.

If I drop it to 4 knots, I burn one half gallon an hour. This means 24
hours of constant use and nearly 100 NM of range. (It's a
racer-cruiser, not a passagemaker).

I only use full throttle in reverse, actually...if ever.

The point? You pay hugely in fuel consumption and engine wear getting
that last knot.

R.