Most efficient cruising rpm?

[Louky]

This is the first year I've owned my 87, 32' Fisherman with twin Chrysler 360's. I've been searching for some kind of chart on most efficient cruising rpm with no success. Can anyone tell me where to look, or give me some advice? 2600 rpm feels good, but am I wasting fuel without gaining much more speed?

Thanks for any help.
Louky

[balthaus]

LouKy,
Here is a little info on engine efficiency. It seems like a while ago it was a little more complete ( more models and engines ) but I could be wrong.

http://www.marinette.com/perf.htm

[Louky]

Thanks for the reply balthaus. The ratios are probably similar, but hopefully I'll be able to find the same type of stats using the 360's.

Thanks again
Louky

[balthaus]

Kinda what I thought as well.
I am going to look at an 84 32' sedan flybridge with twin 360's this weekend.
Not sure of the props that are on her but just for the quick math I figure efficiency should, or could, be similar to twin 318's...unless one were to really open them up.

[barkleydave]

Off plane best you will do on both engines is around 6 gph both engines @ 1600 rpms 8.5 mph-
One engine 3.5 gph @ 1600 7.2 mph

rough estimates

On plane 2400 expect 14-16 mph 6-7 gph per engine.
again rough est. based on fuel, water, waste, gear passengers etc;


safe harbors,

dave

[bruegf]

I installed fuel flow gauges when I bought my 32 sedan flybridge w/ 360's and as expected the most efficient rpm varied depending on load (gas, people, water, gear, etc) and water conditions, but in general my most efficient cruising rpm was in the 1700 - 1900 rpm range and fuel consumption was anywhere from .9 (heavily loaded in rough water) to 1.25 miles per gallon (lightly loaded in smooth water)

Fred

[Louky]

I cruise a lot in the high teens. Seems like it just moves along nicely at that rpm and doesn't throw a huge wake, so 1600-1700 is good news. When I brought the boat down river from Cincinnati I was cruising along at 2650rpm and 19mph down river. I'm hauling it out this winter and clean up the bottom and props, so I'm sure efficiency will improve next year.

Thanks for the help!
Louky

[tundrarules]

What about trim? Trimming the nose down will produce drag with the trim tabs. Boat is most efficient with no trim. Thinking you could get a 1/4 mile better with no trim. Just an educated guess looking at other forums. You guys with the fancy fuel meters chime in and do a test for us.



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