Fuel Usage - 310 Dancer

D

Double D

New Member
Jun 9, 2008
4
I just completed a trip from New Orleans to Orange Beach, Alabama - the first long trip in the boat since purchasing it in December, '07. I was expecting to burn 15 to 20 gph based on the previous owner's input. However, it appeared I used between 25 and 30 gph. I generally traveled at 3200 rpm, 20 to 21 mph. The bottom was cleaned when I purchased it and the paint was relatively new. I use it regularly, so I don't expect much marine growth. Any input would be appreciated.

Randy
1999 Sundancer 310
5.7L, V Drives
450 hours
 
How many people on board? Did you have full fuel and water? The numbers you actually got seem about right to me, the ones you were expecting seem way too low.
 
Hey Barry, you replied to my question about cruising from Palm Beach to Key Largo, just curious if you have made the trip down and how hard would it be for a novice?
I wanted to get waypoints to avoid the shallow areas down in the Keys.
 
I burn 20 gph religiously on trips a few hours long at 3400 rpms. Of course this is in decent weather, 2 people, water tank half full, fuel tanks completely full and no growth. I have 350 mags with v-drives.
 
Thanks for the replies. It looks like the usage numbers vary. I did have a full water tank, empty holding tank. Fuel tanks were full. 3 people on board. The seas were choppy, but able to easily maintain cruising speed. Jackson's 20 gph is what I expected based on my short runs in the lake prior to this trip. An earlier post, of 1 to 1.25 mpg is consistent with my expectation of 15 to 20 gph. I'm going to have the bottom checked out before I return next month and see if it makes a difference.
 
Hey Jackson, I have the same boat and I burn around 25 gph at 3600 rpms with 3 people on board, full fuel tanks and clean bottom. If I run at 3400 rpms I am on the edge of falling off plane depending on the seas; 3600 rpms just seems to be the sweet spot for me. Maybe if I lost the third person I could cruse at 3400 rpms.:huh:
 
My 350 Mag's are burning 24 GPH at 3600 RPM's. The 350 Mag's are going to burn on plan in the 20's.
 
I burn 29 - 31 GPH at 37 - 3800 rpm. I have a NavMan fuel monitor to confirm that this is indeed the sweet spot for the boat.

Boat fully loaded.

Please do not calculate how many $/hr it is.
 
BoatTooSmall said:
I burn 29 - 31 GPH at 37 - 3800 rpm. I have a NavMan fuel monitor to confirm that this is indeed the sweet spot for the boat.

Boat fully loaded.

Please do not calculate how many $/hr it is.
Click to expand...

I will make it easier for you, if you had that boat with that fuel consumption here in the UK you would be paying well over $300 an hour. So now you should feel better :thumbsup:
 
First, you have to divide the other way. He's burning more gallons than the miles he's getting, so it's not 1.25 but something like 0.75.
The 5.7L engines burn up to about 18 gph at WOT, which would be 36 gph max for both.
I have a single in a 26, but I can't really run under 10 gph - although I'm getting 2+ mpg in the cruising range. So, fuel flow won't get any better.
Of course, you have a bigger, heavier boat. And, V-drives aren't nearly as efficient. (I have an Alpha sterndrive). I think that boat also has prop pockets, which don't improve things much either. So, overall, maybe not bad.
But I would still be curious to experiment with trim tab position, then start looking at the props. Are you reaching the proper WOT rpm? Did you have the props checked and serviced after you bought the boat? You can often gain some improvement in the propping, but you have to get everything else right first.
 
Cap10Pat said:
........The 5.7L engines burn up to about 18 gph at WOT, which would be 36 gph max for both.....
Click to expand...

Where did you get this information?

I figure by actual gallons to fill up, GPS miles and speed, and trip RPM's and my sweet spot is 3,500 to 3,600 RPM's, 27 to 28 MPH which equates to about 29 to 30 GPH.
 
Any given engine model can only burn so much fuel. Engine makers usually provide fuel burn charts, and boat reviews usually report fuel and speed results. I have a 5.7L 4bbl and an interest in the 5.7L engine. 18gph is about the max you will see. I'm not sure about the 300 HP version, which is fuel injected, although it can't get much higher. I think it spins faster (to a higher WOT) which may affect fuel burn. I find it helpful to know the max fuel when trying to talk about fuel rates.
 
On my last trip that took about 2h:20m-2h:30m I've burned 30gal on each eangine. This makes it like 27-26GPH. This was on the ocean side with 2-4' seas, cruising at 3700-3800RPMs speed ranging 23-25MPH.

Alex.
 
Cap10Pat said:
Any given engine model can only burn so much fuel. Engine makers usually provide fuel burn charts, and boat reviews usually report fuel and speed results. I have a 5.7L 4bbl and an interest in the 5.7L engine. 18gph is about the max you will see. I'm not sure about the 300 HP version, which is fuel injected, although it can't get much higher. I think it spins faster (to a higher WOT) which may affect fuel burn. I find it helpful to know the max fuel when trying to talk about fuel rates.
Click to expand...

This is incorrect.
A general rule of thumb which applies to ALL gasoline powered engines is that they will all burn approximately 10% of their HP rating in gph at WOT.
A 350 c.i. engine, @ 275 hp (used to own one) will burn approx. 26-28 gph at WOT.
My Chris-Craft has a 6.0, 375 hp MPI engine and burns 37 gph at WOT. Both of these numbers per the FloScan on that boat.
 
Tobnpr,
Your rule-of-thumb has certainly not been my experience. I can't burn even 18gph through my 5.7L. And the example above from Alex is on the order of 12-13 gph only a little below WOT in a 31 ft.

The only thing I can think of is that your flowscan, for all of your numbers is not correct for the fuel plumbing on those engines. Some gas engines, like your diesels, return some of the fuel to the fuel tank, or recirculate it in some manner, usually through a cooler. So you may not be burning as much fuel as you think. (That's the good news :>)

I did allow that some modern high-output engines with fuel injection and higher rpms burn a little more, but not that much. If you were burning 28gph through a 5.7L ... naaah.
 
Most motors will not reach the 10%/ hp analogy. My 502 burns about 34gph at 5050 rpm. It is rated at 415 hp at the prop. If you talk to the high perf engine builders, they'll confirm the 10%/hp fallacy. They do this through practical experience, as well as dyno's and flow meters.

There are a lot of misconceptions about fuel burn and engines in boats. They are repeated in print quite often.
 
You must log in or register to reply here.

Forum statistics

Threads
113,247
Messages
1,429,241
Members
61,125
Latest member
Bassinbradw
Back
Top