How far to push it past Empty...

[hcooperrn]

Went out our final time yesterday, air and water were both 52*, loving the heaters and the dry suit. Schedules just aren't going to let us get out anymore, so I winterized yesterday.

That let me do the final math this morning on the first season. 65 hours, averaging fuel use came in at 5.99 gallons per hour (5.48 since O2 sensor replaced). Does that sound about right for surfing at altitude (SurfXL +500lb, Acme 2419@3100rpm, 4 adults+kids)?

We routinely ended our days on E, however, I usually never filled with more than 26 gallons (usually around 4-5 hours of engine time). I know that the fuel gauges are notoriously off.

The question I have is just how far can I push it before the pickup starts to struggle and I'll be sweating to get it back on the trailer? Even playing it safe with 7 gallons per hour, with a 48 gallon tank, by the math, I should have 6.5+ hours of engine time. Do I need to have a reserve of 5? 10? gallons to make sure it always has fuel available to load on the trailer. I know I can plow bow up to get fuel to the back of the tank, I want to be sure I can idle and maneuver with any stumbling.

[freeheel4life]

That's a tough question. Never really like to play the fuel game as I hate getting towed so always run lots of fuel.
What I can tell you for sure is that in tank fuel pump goes right to the bottom of the tank. It's a big springloaded pickup that pushes against the bottom of the tank and just has two small plastic pieces to keep pickup from sucking a vacuum against the bottom of the tank and blowing the fuse (had a pump break the two plastic standoff pieces so that's how I know). So as you said bow high would get you more fuel for sure, but the pickup is very close to the bottom of the tank.
Just out of curiosity, why are you only putting 26 gallons in a 48 gal tank and then pushing it on fuel?? Only reason I could guess is tow vehicle, but you've definitely got me curious.

[hcooperrn]

Sorry -- the ~26 gallons is all it takes to top it off after it reads Empty on the water, meaning I'm reading Empty with 22 gallons still in the tank. I'm not pushing it in reality, just pushing it in terms of what the gauge says and being overly paranoid.

No tow vehicle issues, I upgraded to a Ram 2500 this year as well, and am exploring in-bed options to haul extra boat fuel as well.

[freeheel4life]

Gotcha. I'm wondering if somehow the wrong sender got installed in your tank and you don't need a longer one. Float is obviously bottoming out on it's shaft well before the bottom of tank if that's the reading you are getting at the helm. A longer sender may just be your answer, or at least would provide you with more accurate data.

[outkastmunkey]

Also when you are filling are you sure your getting all the way full and not stopping just after the first time the pump clicks off? Fill my boat take forever once it hits about 50% full I have to pump slow and stop to let it vent to get to 100% full. Or I guess if your gauge read full when your done that's your answer.

[hcooperrn]

Yep, gauge always goes to full, after the first click I can rarely get much more in after allowing some venting time, I think I have a pretty good vent system, way better than our previous 22v.

Interesting thought about the sender, I assumed it probably all came as a unit and nothing too specific. Don't suppose anyone has any part numbers that I could verify against?

[freeheel4life]

They are all tank specific. Just a float that slides up and down on a rod that varies resistance. Would be easy enough to confirm if your sender is too short for your tank. Pull it out and measure from flange at tank to bottom of rod. Then measure tank from bottom to top. Believe they tanks dimensions are on label when you lift floor as well. IF you decide to remove sender and look into it matchmark sender to tank. It is a "clocked " unit, screw holes to tank mount at flange aren't symetrical, so you can save yourself some time and hassle by marking it. There are some universal sender replacement that allow you to trim float arm length to the tank size, but as your boat is a 2017 i wouldn't explore that route.

[KoolAid]

Go into dealer settings and make sure the boat selected is the Z3. If you have a Z1 or RZR selected it will show the wrong range therefore your gauge will stay incorrect. Just something to check.
Got ahead of myself. Does it show 100% when full and 0% when empty?

[hcooperrn]

How far to push it past Empty...

100% when full, 0% when around 20gal left.

Last time I was in dealer settings it was on Z3; I can definitely check again.

Sent from my iPhone using Tapatalk

[majestic]

My boat was taking 5 extra gallons after the pump shuts off .

[007]

For what its worth, I think the fuel sender is on the port side of my tank, I swear it reads less when listed to the goofy/starboard side. I've run mine down to zero, been sweating bullets on the way to the dock and still only put 30 gallons in the tank on a '15 Z3. And it's a 48 gallon tank. 25-30 gallons brings it full again per the gauges.

Many moons ago, I was behind the wheel of a buddy's jet boat. We had been surfing until on fumes and big storm was rolling in on us. Girls on the bow, guys in the captains chairs. Ran it sticks to the firewall down the lake long past when it read empty. Hit the now wake zone and it puttered out of gas...well beyond the dock. Is so happened a couple of jet skis were coming in and were kind enough to tow us to the dock as the lightning came down. Girls come back in the cabin from the bow and for what ever reason my buddy thinks to try the key. Starts right up! Pickups were in the back of the tank...once the weight shifted aft we had enough gas to maneuver at least. Now that I tell that story, I need to look and see where the pickups are on my Z3 incase I ever run it that low!

[hcooperrn]

Thanks 007, sounds like ours work/read the same way.

Majestic -- I may just be lucky with my vents. I've tried a few times after the first click to get more in, waiting up to a minute, and always hear it filling the tube right away and clicking off again, I'm pretty confident I'm getting it full every time.

I'll snap a pic of the sender and pickup location as soon as I can -- I know location wise the pickup is closer to the back, sender just aft of mid-tank, that probably plays a part in all this. I'd like to think that given location, depth, and tank size, one could calculate the actual usable volume available at a given angle.

Also thinking based on freeheel's description that while bow-up will help, if it does stall, calm and level is going to let you suck the last bit out, hopefully letting you get in to a dock?

I guess I could be a bit more practical about this; next year I could just take out 10-15 gallons in cans and run it until it quits, then I would know for sure. I'd like to plan a Powell trip next year, though it would be land-based, so need to stay within range of fuel, that's what is peaking my curiosity on wanting to know just how far I can go and how long I can play.

[freeheel4life]

Running her dry with a couple cans on hand would definitely get you an answer. There's always variable in the whole equation as well. Obviously ballasted surfing consumption is much more than un weighted planing.
Not that I ever trust computers, but did some diagnostics with computer in boat on a z3 with a PCM 409, heavily weighted, Ronix shaper, and while surfing ECM says consumption was 19-20 gal per hour. Interested to see where this all leads. Wish there was a better way to tra k data.

[TigeFamily]

Maybe not easy to track with computer, but I have tracked my fuel consumption all summer (every fill up I write down how many gallons I put in and exactly how many engine hours during that period...its easy cause I fill up every time I got to lake at same station)....also with a PCM 409 in 24ft boat. I have averaged 4.5 GPH no matter what I do, tho most of it is heavily weighted surfing (4700lbs), with a Nauticurl suck gate. Interesting that ECM shows such a high consumption rate cause my hull is similar to a Z3 (Enzo SV244). I have always heard that Z3's have similar to mine and average around 5GPH due to efficiency of convex hull.

[freeheel4life]

Maybe not easy to track with computer, but I have tracked my fuel consumption all summer (every fill up I write down how many gallons I put in and exactly how many engine hours during that period...its easy cause I fill up every time I got to lake at same station)....also with a PCM 409 in 24ft boat. I have averaged 4.5 GPH no matter what I do, tho most of it is heavily weighted surfing (4700lbs), with a Nauticurl suck gate. Interesting that ECM shows such a high consumption rate cause my hull is similar to a Z3 (Enzo SV244). I have always heard that Z3's have similar to mine and average around 5GPH due to efficiency of convex hull.

I'm sure that the actual average is much lower. During turnarounds and what not fuel consumption was much lower according to ECM, cant remember what GPH were exactly but seem to remember low single digits.That's just what it said it was doing at peak consumption, I would assume that if fuel pressure and injector pulse time is known by the computer it could easily give a solid GPH #, but that's getting beyond my technical knowledge. This z3 lives up around 5000ft, is running 1200lb enzo on top of tanks and additional throwover bag when boat is light on people, and at the time was propped with a 1235. Have since switched customer to a 2079 and he's much happier, curious to see what ECM thinks about it as far as calculated consumption rate.