What's your 'guess' on fuel usage between these boats?

[paulspaddle]

Here are the two boats.
#1.
1990 Glastron 175 (17.5') with a Mercruiser 4.3. Mid-hull design, 2000lbs.

Sorry, not a great pic of hull and boat, but you get the drift.

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#2 1982 Webbcraft 21' with a Mercruiser 5.7, Deep-V design, 3000lbs.

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Say we use the Glastron for tubing 60%, skiing 10%, touring 30% of the time it was used. Approximately 3-4 hours per day for 7 days. I average 7 gallons per day in fuel.

This isn't exactly science, but what percentage would you 'guess' the Webbcraft would use more in the same week with the exact same usage?

 

[Limited-Time]

Re: What's your 'guess' on fuel usage between these boats?

I would guess between 25 to 35% more. Depending on propping and on how heavy your right hand is.

 

[paulspaddle]

Re: What's your 'guess' on fuel usage between these boats?

Not to be mean but if you are buying a boat based on wanting to save fuel, maybe you should find another hobby. :redface:

Ah Bubba....don't go down that road...

 

[paulspaddle]

Re: What's your 'guess' on fuel usage between these boats?

I would guess between 25 to 35% more. Depending on propping and on how heavy your right hand is.

Thanks...that's kind of what I was thinking too.

 

[Limited-Time]

Re: What's your 'guess' on fuel usage between these boats?

It will also depend on your load. A larger boat tends to by loaded more. if you plan on additional passengers/gear/supplies. I may use even more.

 

[45Auto]

Re: What's your 'guess' on fuel usage between these boats?

Say we use the Glastron for tubing 60%, skiing 10%, touring 30% of the time it was used. Approximately 3-4 hours per day for 7 days. I average 7 gallons per day in fuel.

Something is wrong with your fuel usage numbers above. A brand new fuel-injected 4.3 will use at least 5-6 gallons PER HOUR just cruising around. A carbed 1990 will use even more. No way it'll cruise for 3 hours on 7 gallons. Tubing and skiing will make that number worse.

As others have said, expect the 5.7L to be 25% worse in reality.

But if you really think your 4.3 only uses 7 gallons in 4 hours of cruising, expect the 5.7L to be about 400% worse ....

 

[paulspaddle]

Re: What's your 'guess' on fuel usage between these boats?

Something is wrong with your fuel usage numbers above. A brand new fuel-injected 4.3 will use at least 5-6 gallons PER HOUR just cruising around. A carbed 1990 will use even more. No way it'll cruise for 3 hours on 7 gallons. Tubing and skiing will make that number worse.

As others have said, expect the 5.7L to be 25% worse in reality.

But if you really think your 4.3 only uses 7 gallons in 4 hours of cruising, expect the 5.7L to be about 400% worse ....

I always appreciate your impeccable reliance on facts and numbers.

Lets not drag this down, but what I said was "approximately" 3-4 hours per day. I was looking at our 'average' over the entire week. Some days we used it more and somedays we used it less. (or not at all)

I was purposely being very general otherwise it would be a long detailed post...that's why I said, "this isn't exactly science"....just a general opinion was all I was looking for.

As we know, talking about fuel and boats can be a touchy subject....I'm keeping it light boys....

 

[45Auto]

Re: What's your 'guess' on fuel usage between these boats?

I always appreciate your impeccable reliance on facts and numbers.

Don't you just love math? It's just so neat the way 2 x 2 ALWAYS equals 4, no matter how many times people claim that it equals 5 or 7 or some other number on their boat!

 

[paulspaddle]

Re: What's your 'guess' on fuel usage between these boats?

Don't you just love math? It's just so neat the way 2 x 2 ALWAYS equals 4, no matter how many times people claim that it equals 5 or 7 or some other number on their boat!

You nailed it! I'm hesitant to even be sarcastic on this topic because before we know it were talking Merc 470's or something.

Say, do you have a graph on consumption/rpm for 5.7, 5.0, 4.3?

 

[dirtyoldman]

Re: What's your 'guess' on fuel usage between these boats?

You nailed it! I'm hesitant to even be sarcastic on this topic because before we know it were talking Merc 470's or something.

Say, do you have a graph on consumption/rpm for 5.7, 5.0, 4.3?

that bigger boat is about like my sea ray. I'd use 15-20 gallons using the boat heavily for 3-4 hours. I'm about 8 gph at cruise of 3300 RPM, at 35 MPH. You've got some accelerating with the tube and a lot of shut down and idling time, so that's my guess. I bet the smaller boat is 10-15 gallons for the same useage.

 

[paulspaddle]

Re: What's your 'guess' on fuel usage between these boats?

that bigger boat is about like my sea ray. I'd use 15-20 gallons using the boat heavily for 3-4 hours. I'm about 8 gph at cruise of 3300 RPM, at 35 MPH. You've got some accelerating with the tube and a lot of shut down and idling time, so that's my guess. I bet the smaller boat is 10-15 gallons for the same useage.

Thanks for the first hand connection.

Yes, there is definitely 'down time' when skiing and tubing. The reality is you tube for what?....10 min, shut it down, change participants, yak yak yak, someone else goes for a tube or ski, shut down, hang out.....rarely does the motor actually run for 3 hours straight.

 

[45Auto]

Re: What's your 'guess' on fuel usage between these boats?

Boattest.com has hundreds of tests on different boats. I graphed 3.0L, 4.3L, 5.0L, 5.7L, and 8.1L bowriders. Doesn't matter how many you look at, you'll see the same trend plus or minus 10% or so. In the 17' to 22' bowrider range, little boats will be in the neighborhood of 5 MPG, bigger boats will be in the neighborhood of 4 MPG. This is why you're seeing the 25% number from different posters.

If you want to go 50 MPH, you're going to get about 3 MPG no matter what you have .....

 

[paulspaddle]

Re: What's your 'guess' on fuel usage between these boats?

Right, that was the site!

Thanks for taking the time Auto45.

 

[badkins50]

Re: What's your 'guess' on fuel usage between these boats?

You nailed it! I'm hesitant to even be sarcastic on this topic because before we know it were talking Merc 470's or something.

Say, do you have a graph on consumption/rpm for 5.7, 5.0, 4.3?

now, now paul. easy does it on us 470 guys. we can't help it, after getting pick on all the time, we can get just alittle hard headed sometimes . I can cruise, tube and play around all day on my 20 gallon tank which doesn't hurt the wallet (that much) either even at 2.65 a gallon.

 

[badkins50]

Re: What's your 'guess' on fuel usage between these boats?

Sorry I just could not resist. Have a good one.

 

[paulspaddle]

Re: What's your 'guess' on fuel usage between these boats?

now, now paul. easy does it on us 470 guys. we can't help it, after getting pick on all the time, we can get just alittle hard headed sometimes . I can cruise, tube and play around all day on my 20 gallon tank which doesn't hurt the wallet (that much) either even at 2.65 a gallon.

It's all good, sorry for the 'shot'....you guys do get beat up a lot.

Actually I saw your boat the other day....does the 21 in the name mean 21' feet? I was wondering how that 470 pushes such a big boat. Those 470's have a good reputation for power, but 21 is a lot of boat.

 

[badkins50]

Re: What's your 'guess' on fuel usage between these boats?

I know it's all good. The 210 is just the model number (don't know how they came up with that). It actual measures 19-1/2' not including the outdrive. The motor at 170hp actually is pretty torquey and planes out very good. We ski and tube all the time. WOT is about 40mph. Just gotta keep up with the maintenance and show it love is all.