To Floscan or Not? - Updated 11/1/13

It's not all about hoping to recoup the investment through fuel savings , though over time a lot of us have done that even with the high-end F/S models.
Don't neglect to also factor in the great personal value of having a very accurate totalizer display of Gallons Used ( after calibration ), as well as the ease of comparing present fuel flow ( or NMPG economy ) to normal or between engines to help notice or confirm suspicion one engine is a little "off" for some reason that would then more strongly support further investigation

For me, the 9000 series was the only real choice because the dynamic NMPG readout in changing conditions is way more valuable than just viewing GPH, but RWS you may prefer not to swap out a tach in your integrated diesel engine dash panel. I really like the easily readable & colorful, backlit, accurate, digital tach in the 9000's vs the original analog tachs they replaced in the same holes.

As a somewhat interesting related note, by checking the F/S's when trimming the tabs I found I oddly get slightly better economy with a very small trim lean to port, and that when the tabs are very close to optimum for any given planing rpm, only about a 1/2 second tap on the Bennett tab switches can be proven to slightly add'ly increase economy via the F/S NMPG display.

Do you or I really NEED these tools. Not really, ....but they do provide appreciable value.
 
quote:
Originally posted by Doc

The boat I just acquired has a set of the deluxe models that are interfaced with the gps and give both gph and mph. The problem is that one has been cut off because...I think... it ingested water and quit working. I know that the boat fuel vents had to be moved when it was new because water would get sucked back up the vent line into the tank at certain speeds. They were located almost back to the transom on both sides.

Repair people for these things appear to be hard to find. I have not had any luck with my casual search for an expert in SW Florida.

Now I look at the working one and double it. Have not filled up since I started keeping a fuel log so I don't know how accurate it is but it certainly will tell you where the sweet spots are.

Click to expand...


Doc - Is that boat gas or diesel-powered?

If by a by chance gas, I wonder if your F/S's may possibly have the old, long-obsolete model #264 senders that had rubber diaphragms that ethanol rapidly destroys. The replacement for the #264 is the #20B sender( for I/B engines to 350hp with reliable paddle wheel flow sense instead of diaphragm.

Note also, if a F/S display stops reading properly it can often help to simply remove the multi-wire connector from the back of the display gauge and plug it back in a few times to clean off minute pin corrosion.

Other problems may include :
-air getting into fuel lines up stream from the sensor,
-fuel line just downstream from the sensor not supported with uphill flow to prevent trapped air at the sensor,
- or corrosion at the sensor pigtail- wire splices .

Since you apparently have 2 9000 series like mine & one of yours still reportedly works fine, just momentarily swap the connectors at the back of the dash displays if possible to help decide whether the issue is the sender or gauge.

If sender is bad, note the color of the plastic top or end cap which likely has the model # on it , just order a new one from FloScan at the Factory Price & replace the bad one.

http://www.floscan.com/html/blue/accessories.php
 
quote:
Fact is my real burn rate is far lower than the published data.
Click to expand...


Rereading all this again causes me to suspect that you are using the engine fuel curve not the prop demand fuel curve. Engine fuel curve will always be more because that is the max output at any rpm while prop demand fuel curve is closer to what the engine is actually doing. They will be equal only at max rated rpm if you are propped right.
Also one of your curves shows about 4300 rpm while the charts seem to indicate max rpm of 3800. Underproping will also reduce fuel at a given rpm at the cost of speed. What is max rated rpm??

how does the fuel you use compare to the prop demand fuel curve??
 
Originally posted by pdecat

quote:
Fact is my real burn rate is far lower than the published data.
Click to expand...


Rereading all this again causes me to suspect that you are using the engine fuel curve not the prop demand fuel curve. Engine fuel curve will always be more because that is the max output at any rpm while prop demand fuel curve is closer to what the engine is actually doing. They will be equal only at max rated rpm if you are propped right.

It's been a while, i'll have to examine the data to confirm that.

Also one of your curves shows about 4300 rpm while the charts seem to indicate max rpm of 3800. Underproping will also reduce fuel at a given rpm at the cost of speed. What is max rated rpm??

the max RPM numbers are consistent. When first released the max governed speed on these engines was 3800. It was later revised to 4000-4100.

how does the fuel you use compare to the prop demand fuel curve??

That is difficult to quantify, as we run various speeds. When I stick the tank I am constantly surprised at how much fuel is in there when based on the "trip" we should have burned more.

THAT is the consistent factor.

As far as the underpropping, when we first did the repower we ran our prop calculations for a 12,500 lb boat. (dry weight) and installed a pair of 4 blade 21x19. swinging those resulted in a slight overprop, as the actual loaded weight with all the deck furniture, genny, fridges, wet bar, spares and tools & etc changed the actual loaded weight.

Those props became the "spares" and the actual props we're currently swinging are 20x20 (HJ739 20x20 R4 1.5" Bore No Cup 0.72 DAR Nibral)

with all that said, perhaps the biggest difference since the repower is her running angle. Her a$$ gets out of the water like never before. Application of the trim tabs has ZERO effect on GPS speed. ZERO !

The only conclusion I have is that the diesels increased torque and larger props (vs. the gas) have provided additional lift, resulting in far better economy/performance than anticipated.

Does that make sense?

RWS
 
I'm just reading this thread and since I've considered Flowscans but realized I don't run enough to make it worth while I'll ask you what changed my mind. How many hours a year do you put on your engines? If you run 100 plus hours a year then yes you will benefit from Flowscans, 50 to 100 hours not so much and less than 50 hours they won't help you. If your running from St.Pete down to the Keys it sounds like you will benefit from the feedback the Flowscans will provide. I'm guessing your converting from gas to diesel was also the same reason your thinking about Flowscans. Rob
 
Sure it makes sense but if you are underproped then you won't load the engines along any published data curve and use less than expected fuel. E.g. You could run at 3000 rpm for weeks in neutral and use little fuel. Remember the eengines are rpm limited so if you were under propped WOT will always be the same.
Underpropping is good for engine life but not speed.
If you propped for 5000 rpm you would not reach that because of rev limiting but fuel use at any rpm would be way below the prop load fuel curve because you would be operating on a much lower load curve
 
You put a lot of bucks in the boat to get where your at. As a percentage of your investment a couple of FloScans won't amount to Diddly Squat. What the hell are you waiting for?
 
When I first got my boat I too wanted flowscans but after learning to calibrate the gauges atti up I realized I knew enough to predict how much fuel I had used. The only things couldn't do was pick the best rpm so I used the rpm where the speed vs rpm curved down figuring fuel use on plane was too much to worry about small differences
 
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