Port and Stbd Fuel Flow info - Menogot

[oldmako69]

2005 F225TURDs.

When I peruse the owners manual, they suggest that there is a P and an S designator on the fuel flow management gauge. This allows one to toggle between the two engines for individual burn, and display both P and S for combined fuel burn.

I have no P. I have no S. I have no PS.

I do see fuel flow for ONE of the two engines, although which one I cannot say. I realize that these are fairly efficient engines, but there is no way that two engines are burning about 10 gallons per hour (total) while running at 4000 RPM and pushing a 5-ton boat, so I am convinced that I am looking at but one engine fuel flow.

There are what appear to be fuel transducers located on the fuel lines from the tank, to the fuel selector valves, so I'm guessing that I am supposed to be able to discern actual flow.

On a brighter note, they are both turning 57-5800 RPM and running great. I had a low-speed misfire on the port engine and replacing the plugs cleaned it right up. Idles nice and smooth now, though the Starboard engine still quits for no reason sometimes. Somedays its perfect. Other days, less so. Knocked the hell out of a dozen big fat red drum this week and put ten hours on them.

[panasonic]

Could you not just run one engine at a time to determine which engine is showing it's fuel flow? Then go from there to determine why the other is not?

[rodbolt17]

if it was rigged correctly and both transducers are working it will have a p and an s and a both.
you have to push buttons to use it.
a pair of 250 2 smokes will burn about 50 gallons an hour above about 4800.

[oldmako69]

Panasonic -

Yes, I can get the one engine to display fuel flow. I assume one side is the master, probably the standard rotation (F225, not LF225) engine. But even it is supposed to display a P or S while running. It does not. The gauges don't show any ghosting either, as if they've never displayed it. My dilemma is more of a curiosity since I am not hell-bent on tearing into anything, especially if expensive parts are involved. As it is now, I do have fuel burn displayed for one engine as well as gallons consumed total and MPG. I just double the burn figures for my at speed burn and total the consumed valued for fuel used. I just cut the MPG in half for a wag. Seems to be 1.6 or so for the way I run the boat.

My last fill up had me guessing at about 80 gallons since the total consumption displayed was about 37 gal. This total did not include a short booze cruise after the fill up since I had neglected to reset the totalizer. I ended up pumping in 82 gallons.

I remember that on the sea-trial, the previous owner was trying to convince me that 10GPH was total fuel consumption at 3800 and 30MPH so apparently, he never had actual fuel burn figures either. Funny guy.

YAM has a fuel burn calculator that backs up my experience and guesstimate....http://www.boat-fuel-economy.com/yam...ion-us-gallons



Rodbolt -

Fully aware that the P and S displays respond to the Mode switch inputs. I get bupkis no matter which combinations of SET and MODE I select. I also don't have trim indications for either engine. Both switches at the tilt mechanism operate freely.

[99yam40]

I am fairly sure Rod was saying that if the gauge is not getting both signals, then it will not show there are 2 sending units,
so you do not get the P&S

[boscoe99]

I am fairly sure Rod was saying that if the gauge is not getting both signals, then it will not show there are 2 sending units,
so you do not get the P&S

That is correct. If only one sender is providing data to the FMM then it thinks it is connected to a single motor. No display of the motor(s).

With two valid sender inputs then PS, S or P are available for display.

[oldmako69]

OK. Perhaps at this point, the next thing to do is pull and test the sending units. Or, the one that is determined to be inert.

[panasonic]

Or just keep on trucking and the times two equation.

[rodbolt17]

or simply take it to a shop with a master tech that can fix the rigging issue.

[pstephens46]

or simply take it to a shop with a master tech that can fix the rigging issue.

You may not realize the Op is less than 1 1/2 hours drive from your shop. He may drop it off in your front yard!

[oldmako69]

More like 2.5 hours and my truck won't make that pull, so it will get fixed in situ or it may just be a math exercise, depending on how much other work I have to do. Besides, I'd rather fix it myself if I can. In over 40 years of boat ownership, I've only had a pro work on my boat one time. That was to have the seals replaced on a 1977 OMC 85 lower unit. I am far from a tech, but I do take satisfaction in keeping my boats running with my hands, and my tools. I got a hell of a deal on an extremely lightly used and garaged boat with low time. But that only means that there is money left over for the inevitable repairs from a lack of use and improper pickling.

Of course, I have schlepped starters, alternators, and carburetors to reman shops and sails to a sailmaker, but that's it.

It may not be a rigging issue. It may be as simple as a busted fuel flow transmitter. So I have some work to do before I toss in the towel. But I do appreciate the advice.

[rodbolt17]

you do understand that flow transducer is a simple 5V square wave generator?
it is stupidly simple to test. do you have a ground?
do you have 5V to it?
does it generate a 5V square wave when the paddle moves?

[oldmako69]

you do understand that flow transducer is a simple 5V square wave generator?
it is stupidly simple to test. do you have a ground?
do you have 5V to it?
does it generate a 5V square wave when the paddle moves?

I don't know the answer to any of those questions. I am not a trained mechanic, I'm an ATP. But many thanks for giving me ideas about where to start, that's what I was looking for when I started the thread.

[rodbolt17]

paper clips and a digital meter that can read Hz are your friend about now.
the frequency of the 5v square wave is what the FMM is looking for.