Long Term GPH Realization

[tpenfield]

When I went from a single engine sport cuddy to a twin engine day boat a few years ago, I was a bit concerned about the increased fuel usage.

I was getting about 6 GPH overall on my 24 footer and was thinking double on my 33 foot twin engine boat.

Now that I am 3 years into the 'new' boat I have taken a look at the fuel usage over the past 3 years. My stats are:

720 gallons
110 hours
Resulting in 6.5 GPH

I had an idea that the big boat was getting pretty good fuel mileage but did not realize it was so close to my old boat :thumb:

I am sure if my 33 footer were a cruiser versus a sport/day boat it would be a different story. Regardless, Not a bad case study for the virtues of a twin engine boat.

 

[littlerayray]

That's interesting but the 2 engines are working less than the single so it kinda makes sense

 

[littlerayray]

Had a guy question fuel consumption about my boat one day and told him if he is worried about fuel consumption then a boat may not be a good idea

 

[QC]

I would bet 17 brazillion dollars that you operate(d) the boat(s) differently. There is a missing piece of data here.... distance traveled. That would give you MPG and average MPH. Both are required for this to be evaluated completely.

 

[smokeonthewater]

2 hour meters on new boat = 6.5 gph per engine thus 13 gph maybe?????

 

[Alumarine]

Had a guy question fuel consumption about my boat one day and told him if he is worried about fuel consumption then a boat may not be a good idea

It is important if you need to know how far you can go with a set amount of fuel.

 

[QC]

^^^^^ I always say I want to know where I am going to run out, not when

 

[tpenfield]

2 hour meters on new boat = 6.5 gph per engine thus 13 gph maybe?????

No, the 6.5 gph is combined. My boating habits are substantially the same . . .cruising, tubing, etc. The only thing we do not do with the 33 is wakeboarding.

We tend to go fast with the 33 than we did with the 24 . . . maybe 5 mph faster on average as the longer hull carries better through the chop where as the 24 would tend to nose dive a bit more.

 

[QC]

Some of this, but hard to believe all, is carb vs. MPI. But I think I will sum this up as we all needs twins!!

 

[JoshOnt]

What speed and rpm would you say is your average?

 

[tpenfield]

The big difference with the twins that I have noticed and may be contributing to the fuel efficiency is that the boat does not fall off plane like a single tends to do in rough conditions. The twins run like the boat is on rails and just plows through everything with little/no variation in RPM or speed.

So, I can cruise across the bay in 2-3 foot chop at 2500 RPM and going 27 mph with the twins, whereas the single would be at 3K+ RPM to do the same in the 24 footer, and the speed would tend to fluctuate, so it would need a bit of throttle now and then to keep it going.

 

[cptrick3]

I once had a 10 meter Trojan(13' beam) with twin 454's. It had a 320 gal fuel tank. My current 24' Chaparral has a 74 gal tank. I think there's a reason for that.

 

[milehighjc]

This is something I have been tracking, but have no reference points. My Crownline 182 with a 5.7L 2bbl carburated is running an aggregate of 3.3 GPH with a range from 3.13 to 4.06. The boat is pretty heavy, and Im typically running with 4-5 adults + gear, beer, and food. Not surprisingly, there is a strong correlation between High GPH and a high level of water sports. I have NO idea if that is running well or not - sometimes it seems to me like it is it is running a little rich, but Im never sure.

And yep, I do keep a log. Insane I know, but Im a data guy.

 

[littlerayray]

It is important if you need to know how far you can go with a set amount of fuel.

Yes but I also follow the one third rule and on long trips like from cornwall to kingston I do the half rule once I'm at half I start looking for a fuel stop but I always follow the one third rule

 

[dingbat]

The big difference with the twins that I have noticed and may be contributing to the fuel efficiency is that boat does not fall off plane like a single tends to do in rough conditions. The twins run like the boat is on rails and just plows through everything with little/no variation in RPM or speed.

.

Little to nothing to do with twins. Everything to do with the increased displacement. A single inboard diesel with equalize the torque would probably be even better

 

[QC]

Two engines with double the weight and double the displacement (same each) fixes what? Diesels are always better on fuel if all else is equal.