Fuel Capacity


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ParaDocs

New member
I own a 2021 34PC. I'd like to have an accurate measurement of my fuel capacity.
The specs say it has 190 gallon capacity. When I reached out to Formula they said they allow 10% for expansion so that I only have 164 gallons usable. That math doesn't make sense to me because 190 - 10% = 190 -19 gallons which should allow me with 171 gallons usable. Not sure where they came up with 164.
Other issue is the fuel capacity reading on my Mercury monitor does not correlate with what I can fill up with at the actual pump.
For example: When I fill up at the pump the Mercury seems to max out at 160 gallons - give or take a few gallons (sometimes it will say 157, the highest it ever reads is 161). The gauges above the monitor seem to max out at about 19/20ths never quite going all the way.
However when I actually fill up at the pump it does not correlate with the amount on the display.
Some examples: 1. Recently went on a long trip - started with full tanks - reading 160 gallons on my Mercury display - when I arrived and came off plane it was reading 0 gallons. When I filled up at the pump it only allowed me to put in 145 gallons which brought me back up to reading 160 gallons. This is a discrepancy of 15 gallons between the change on my display & the actual amount of gas I could put in.
2. On the reverse trip - again started with full tanks - reading 160 gallons - when I arrived it read 7 gallons. A the pump it only allowed me to put in 140 gallons to bring me back up to 160 gallons. In this case a discrepancy of 13 gallons (i.e instead of needing 153 gallons to go from 7 to 160 it only took 140)

Is this some sort of calibration issue?
Does anyone know the real numbers in terms of usable fuel?
I've heard they keep some in reserve but I would like to have an accurate idea of how much fuel I have so I could avoid any issues.

Thanks for any help

Reply
 
That's one way of doing it but I wold prefer a less "winging-it" method. Are there any after market products that are simple to install & accurate?
 
My 2015 34 PC is supposed to have 2 100 gallon tanks. When filling it never reads above 189, pretty close. (That's when the nozzle shuts off, not when gas pukes out the fill :) ) When filling from approximately 1/2 tank I'll take 35-36 gallons in each tank. 72 gallons total 100 + 72 = 172, Vessel View reads 189. That being said, I thought there was a way to calibrate the vessel view. I never really dove in that far as my readings are pretty close.
 
Hum... My 2007 34 is listed as having a 206-gallon fuel capacity.

From my observations, the fuel gauges are VERY conservative. I believe this may be by design, to keep operators out of trouble. As an example, I can be down to 1/8th of full fuel showing on the gauges, but at that point, I can't get more than 125-130 gallons into the boat. If the gauges were truly linear, I should be able to get 175-180 gallons on board from that level. I've talked to multiple 34 owners who have observed a similar scenario, which leads me to believe it's by design. Difficult to validate though...
 
It's nice having a reserve built in to help keep us out of trouble but it would be nice to have the more accurate measurement. I'm going to see if I can recalibrate it somehow in VesselView to try to bring it more online with reality
 
A couple thoughts:
It may be worth checking the fuel tanks themselves to understand what their true capacity is (without any reserve that might be accounted for in the spec sheet) My 2004 34PC has two 103 gal tanks based on the tank dataplate:
20231004_195512.jpg

I also happen to know (don't ask how...) that if I run a tank dry, then fill it up, I'm short 3.5 gal from that 103 gal total - ie: there's 3.5 gal at the bottom of the tank that I can't get to (at least it's inaccessible when the boat is floating level).

In my experience, if you really want to know, do what you've already done a couple more times - start with full tanks, make a trip or two, track your distance, what Merc monitor is saying... then fill the tanks again so you know what was consumed and do the math.

Cheers, andrew
 
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Observe how far you can go, then use that information.
Almost like the guy who's been boating 40 years said in post #2. ;)
 
My concern is you have to push it right up to the edge & risk running out of fuel to get accurate numbers. In fact to be really accurate you should actually run out of fuel otherwise how do you know how close you are?
As i mentioned originally - my gauges were reading 0 after one long trip yet it only took 145 gallons to bring me back to 160. If I'm reading 0 - kind of scary to keep driving not having a clue what's really still in the tanks.
 
ParaDocs said:
My concern is you have to push it right up to the edge & risk running out of fuel to get accurate numbers. In fact to be really accurate you should actually run out of fuel otherwise how do you know how close you are?
As i mentioned originally - my gauges were reading 0 after one long trip yet it only took 145 gallons to bring me back to 160. If I'm reading 0 - kind of scary to keep driving not having a clue what's really still in the tanks.
Click to expand...
You might not have to go that far - just making a note of what the fuel gauge read and comparing to how much fuel went back in (and therefore what the real fuel level was...) can get you most of the way...
 
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