Fuel Usage - 310 Dancer

Coming back from Bimini to Fort Lauderdale, I burned 64 gallons, in 2.32 hours going approx 3700 rpm and traveling 59 miles. Open ocean and gulfstream seas were 2' or less.

Going over to Bimini I burned 100 gallons, took 3.5hrs hours same travel distance, but seas were 4-5' , sloppy and winds were up...

A lot of factors make up fuel usage.

Barry
 
Barry,
Your fuel consumption wasn't much different on those two trips. You ran almost 50% longer on one trip and burned 50% more fuel.
Yeah, your mpg differed, but not your rate of fuel burn.
I do agree with your major statement though, and never disputed that. I just said that each engine model has a pretty fixed maximum fuel burn which sets some limits that help to understand the main question of this thread.

I don't know about that rule-of-thumb thing, maybe it applies to race boats or something. I was commenting on production 5.7L engines.
 
barryg said:
Coming back from Bimini to Fort Lauderdale, I burned 64 gallons, in 2.32 hours going approx 3700 rpm and traveling 59 miles. Open ocean and gulfstream seas were 2' or less.

Going over to Bimini I burned 100 gallons, took 3.5hrs hours same travel distance, but seas were 4-5' , sloppy and winds were up...

A lot of factors make up fuel usage.

Barry
Click to expand...

You didn't state you RPM's going over to Bimini.
Your speed going over to Bimini was about 16.8 MPH which puts you in the 2,700 RPM range.
Understanding your seas prevented you to go faster, reducing the RPMs put you "OFF" the sweet spot and in a very inefficient place of operation.
 
Absolutely...The sea conditions were changing all the time going over and it was very difficult to keep it at any steady rpm's as we were getting pounded at the normal 3700 rpm's, so we had to back it down and burn a lot more.

I just wanted to show how a change can dramatically affect your fuel consumption and while those conditions were rougher than normal, a lot of times the numbers in the books are taken on too ideal conditions as well...2 people, 1/2 fuel, calm conditions, no winds etc.
 
Thanks for a lot of good info. While in the Orange Beach area last week, I experimented with speed and the trim tabs. On my initial trip, I ran about 3200 rpms. Last week, I generally cruised about 3400 and trimmed the bow down. I don't know my fuel usage, but the boat seemed to run faster with less strain.

Based on several replies, it seems like most run the boats faster. There's nothing in my owners manual about cruising rpms or recommended trim tab use. As everyone can tell, I'm new to this size boat, so I would appreciate some comments on recommended rpm's. With my twin 260 hp's, 3200rmp = 20mph, 3400 = ~23mph (trimmed with the bow completely down).
 
Alex F said:
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.
Click to expand...

Sounds more like 24 GPH total. 2 hours 30 minutes = 150 minutes. 30 gallons of fuel / 150 minutes = 0.2 gallons per minute. 0.2 gallons per minute * 60 minutes per hour = 12 gallons per hour per engine * 2 engines = 24 gallons per hour total.
 
just to add some more data to the discussion. I have a carborated 350 w/4bbl. I got out on a pretty good cruise this weekend, following ion a larger boat's draft. t 3000 RPMs I was buring about 9 gph. At 3400, about 12 to 13. I did pour the juice on for a little, but only to about 4000 rpm and it looked to be about 18gph. Then I was blinded by dollar signs and backed it back down to 3000.
After reading all these numbers, I'm really appreciating my little boat this year.
2.2-2.8 MPG on a calm day.
 
As I'm getting to know my rig a bit better with every trip we take I've noticed that my speedo shows lower numbers than GPS (SOG). As I already noticed a sweet spot of about 3700RPMs the speedo shows 22MPH, while SL530 shows 26-27MPH and C70 shows 22-23KPH (i have two GPS displays).

It looks like both GPS displays are in sync, I guess, that b/c they use the same source (Raystar 125), but they're off from the speedo (I'm not sure if speedo is using spinner or the sensor). Which would you guys trust more, the speedo or GPS numbers?

Alex.
 
Alex F said:
As I'm getting to know my rig a bit better with every trip we take I've noticed that my speedo shows lower numbers than GPS (SOG). As I already noticed a sweet spot of about 3700RPMs the speedo shows 22MPH, while SL530 shows 26-27MPH and C70 shows 22-23KPH (i have two GPS displays).

It looks like both GPS displays are in sync, I guess, that b/c they use the same source (Raystar 125), but they're off from the speedo (I'm not sure if speedo is using spinner or the sensor). Which would you guys trust more, the speedo or GPS numbers?

Alex.
Click to expand...

GPS will always be more accurate.
 
I thought you meant kilometers per hour, which should have been larger. But I guess you meant knots, which should be just plain knots as knots per hour is redundant double-speak, which is also redundant.
 
Sorry if I confused anyone. It's 22-23knots.

Alex.
 
dpmulvey said:
Sounds more like 24 GPH total. 2 hours 30 minutes = 150 minutes. 30 gallons of fuel / 150 minutes = 0.2 gallons per minute. 0.2 gallons per minute * 60 minutes per hour = 12 gallons per hour per engine * 2 engines = 24 gallons per hour total.
Click to expand...

David,
This is very nice way of calculating. If my boat actually burns 24GPH at cruising speed, then 200gal / 24GPH = 8.3 hours of running time until the tanks are dry. Also, if avg cruising speed is 25MPH * 8hrs = 200 miles.

I think this is pretty good. Don’t you?

Thanks,
Alex.
 
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