sunchaser wrote:
Nothing the matter with gizmos, lord knows I*have enough of them. For go fasts burning 20 + gph, Floscans or on engine "computers"*are just the ticket. The assumption though that floscans will yield financial benefit to a small trawler may be a bit fleeting. Your best combination of speed and fuel burn will be at about 0.9 X the square root of the water line length. Even though the constant is 1.34, unless you are a sail boat that constant is at best elusive and likely too high.
SInce few of us want to cruise at 0.9, I use 1.1 to 1.2 for my DeFever and which equates to about 7.8 to 8.0 knots for the approximate 44' water line length. This works out to 1725 - 1750*RPM in relatively smooth water. With a flow scan I'm sure I could improve fuel burn by a tenth or two gph at the most or save about $400 per year. And best you measure the return, even for a Lehman, or your numbers may be gibberish. This all assumes of course that floscans work perfectly, which they do not. If you don't have digital tachs, floscans are even less relevant IMHO.
So gizmo lovers, by all means hook a floscan or two up. Like Ralph Yost, I measure my tanks daily, when cruising, against the installed " tank's mounted yardsticks." It seems to work out to 4. 1 to 4.4*(or so) gph all the time with genset sometimes on, hummmmmmm.
If I could stick my tanks or had sight gauges, I could solve the problem of not knowing reliably exactly how much fuel I have in them.* As it is, I get nervous when the gauges approach 1/4 tank and fuel up when I might not need to.* Likewise, I don't know how close to full my tanks are when I am fuelling.
I just looked and I've spent about $500 per year in fuel so I can't justify a "gizmo" purely for fuel savings, but if speeding up a little only decreased efficiency by a little, I would probably do it sometimes.*