posted 02-18-2005 10:13 PM ET (US)        

"Data Logger [Engine operating hours according to engine speed]
Engine speed          Time [h]
-1000 r/mi            200.9
1000-2000             24.3
2000-3000             9.6
3000-4000             45.6
4000-5000             20.5
5000-6000             0.7
Total[h]              301.6"

I'm not at all surprised at the data. I troll at 7-800 rpm (or 'r/mi' as the computer likes to put it) or drift with the motor idling two-thirds of the time I'm at sea (and on rare occasion I have something edible to show for it). Seas are often lumpy where I cruise and fish, so I've spent a little more than one-tenth of my time at the very unproductive, unpleasant 1000-3000 rpm range, which is under planing speed for my boat and is by far her most uneconomical range as well. Here I'm just banging into wind and waves, zig-zagging across the swells, motor trimmed all the way in and bow further up in the air than I'd like. But finally, at 3000-4000 turns Cetaceous is in her glory at sea...cruising along very comfortably and economically on plane at between about 18 to 28/9 mph, and here I've spent 45.6 hours of my life over the past eight or nine months--the equivilent of a long work week (for a normal person that is, not a lawyer) without lunch breaks...about 15% of my time onboard. The 20.5 hours at between 4000 and 5000 rpm is the number which surprises me the most. My old girl starts to move right along in the mid-to-high 4000 rpm range--32-36 mph--and I didn't realize I spent so much time at those speeds. Probably what I'm seeing is 29-31 mph/low-4000s lake, Petaluma River, and San Francisco Bay cruising activity. Finally, I'm not surprised at all about only 0.7 hours spent at 5000-6000 rpm (actually 5000-5600, 'cause the latter number is the most spins I can get at WOT with my current prop). I barely reach 40 mph/GPS wide open, by the way.

Anyway, hope these data are of interest to someone. They confirm for me many of the things I've discussed over the past year at this website: The nature of the use of a fairly typical, primarily salmon- and rockfishing Boston Whaler skiff mainly in the Pacific north of San Francisco; the efficacy of a 115 four stroke motor on a classic Outrage 18; the great economy that particular motor is capable of delivering, especially because it's being used most of the time (80%+ if my math's right) at its most economical speeds--slow trolling & drifting, and 3000-4000 rpm cruising.

posted 02-19-2005 04:33 AM ET (US)            

It looks like the 4-stroke engine is ideal for you and many other fishermen. Two-thirds of your boating time is done at less than 1000rpm which is very economical for a 4-stroke engine. Have you been able to estimate what your average fuel consumption has been over this 300 hour periode?

Erik

posted 02-19-2005 10:02 AM ET (US)            

Engine Speed vs Percentage of Use
-----------------------------
   < 1000 = 66.6
1000-2000 =  8.0
2000-3000 =  3.2
3000-4000 = 15.1
4000-5000 =  6.8
5000-6000 =  0.2
-----------------------------

posted 02-19-2005 10:22 AM ET (US)            

Tony

posted 02-19-2005 10:37 AM ET (US)            

Funny you should say that about "exploring the upper RPM ranges of that Yamaha a little more." Since I repowered my OR 18 with only a 115 horse power motor, several CW forum members have commented that my boat is 'underpowered.' I've tried to explain that for my uses the combination of a 115 EFI 4/s and an OR 18 seems to be just about perfect. If I were into waterskiing or wakeboarding, or if I needed to make 50 mile runs to get to fishable water, I'd probably (no, undoubtedly) go with a 150 4/s; but the data say it all about my uses and the nice, utilitarian balance provided by a 115.

The strongest--for me anyway--argument made by those advocating a larger motor is that it allows the boat to achieve usual/ideal cruising speeds at lower turns, thus prolonging the life of the motor. As you can see from the numbers, I reach my usual and most economical cruising speeds right where I want, between 3000 and 4000 rpm; and as for exploring those 40 mph wide open ranges (where a motor is redlined and trying its best to tear itself apart), I'll leave that to the tournament bass fishermen and multi-millionaires among us. 30 mph on the ocean is plenty fast enough for me.

posted 02-19-2005 11:50 AM ET (US)            

My reply was meant to be humorous - you know I am a max HP on the transom, WOT most of the time type of guy!

Seriously Tony, it looks like that 115 is the ideal engine for your particular situation. Great info.

posted 02-19-2005 12:18 PM ET (US)            

I'm thinking about trying a lower pitch four bladed prop this season, (Larry/LHG and others are kindly helping me with advice about this decision, though after these positive 'data logger' results, as well as the 'normal' computer readings for all the engine systems, maybe I'll just leave well enough alone). Maybe I'm nuts, but I'd rather adapt myself to the great Dougherty hull design than try to modify it with tabs or 'Doelfin'-like alterations.

Erik,

Unfortunately, I haven't logged fuel useage. I'm loathe to fill up the 63 gallon internal tank completely (because of my probably irrational fear of fuel spills/leaks at the intake port and the concomitant possibility of explosive gasoline fumes), so I've never bothered to check exact before-and-after fuel consumption. Very, very ballpark estimate: During a full day's fishing, including maybe 35-45 miles at cruising speeds and five or six hours drifting or trolling, I seem to use about ten gallons of gas.

Royce,

Thanks for reminding me, though I got another unpleasant $160 (estimate) reminder yesterday from the mechanic who is cleaning out the talcum-powder-like mud from my 8 hp two stroke kicker...thank whatever gods that be that I had the brains to turn off and tilt up my 115 and go to my kicker when it became apparent that we were 'embayed' by mudflats, and that grounding was a real possibility.

By the way, I was listening to a great local program on National Public Radio yesterday about SF Bay restoration planning, and found out that that quicksand-like mud all over the Bay's bottom was caused by the millions of tons of soil washed down from the Sierra foothills and into the Bay during Gold Rush era mining activities.

Tight lines, you Whalers. Think Spring!