Gallons Per Hour

[krisnowicki]

With gas around 3.70 I am buying a new boat and trying to figure out what power package to go with. I have a the 200hp yamaha in my signature below and last week I went about 3 miles and back out fishing and it was 8 gallons I never ever go above 4000 rpms but it just sucks fuel. So I am looking at a base point of an engine that uses about 22 gph at wot and about 13 gph at cruising. So with that as my base I want to go back to the I/O and the big question is between power packages... How much of a difference is the 3.0 4.3 and 5.0 in gas? All of them will be better then my 200 hp yamaha?

 

[achris]

Re: Gallons Per Hour

The fuel consumption of the I/Os is very much dependent of the boat weight, unlike an outboard. As a base line for you to work from, my engine burns between 1.2 litres per nm and 1.5 litres per nm, depending on boat load. Surprisingly that figure doesn't change much between about 2500rpm and WOT.

Hope this helps some,

Chris......

 

[krisnowicki]

Re: Gallons Per Hour

This engine will be in a 18 ft 2400ishlb bowrider... Sorry I should have included that I uses it mostly on light chop in the rivers

 

[abj87]

Re: Gallons Per Hour

The boat in my sig gets around 4-5gph at cruise (20-25mph) and its close in size and weight. i have a 470 but a 4.3 probiblty be similar.

 

[QC]

Re: Gallons Per Hour

My recommendation is to go to BoatTEST.com and take a look at similar boats with the power packages you are considering. Fuel use is probably the least reliable info I see reported here. With that said, both achris' and ab87's numbers seem good.

 

[HT32BSX115]

Re: Gallons Per Hour

This is an I/O forum BUT,

You'll probably get the best economy with an outboard (lighter than I'O's) and an Evinrude ETEC at that... (lighter than most other outboards)

Now, if they'd just put dual counter-rotating props on them......

 

[krisnowicki]

Re: Gallons Per Hour

Outboards from what I understand do not provide as good of the gph as inboards for the horse power they provide. From what I understand yo take the decimal and move it over for an outboard so a 200 hp would be 20.0 at wot and 100 is 10 and so on. And since the cruising speeds are closer to 4000 rpms they need more gas over the day?

 

[QC]

Re: Gallons Per Hour

Not true ^^^^^ much messier picture than your understanding. HT's understanding is more correct. Old carbed, two cycles are thirsty, but there are many exceptions with modern, electronically controlled and injected two and four strokes . . .

 

[krisnowicki]

Re: Gallons Per Hour

So, .... my 1992 200 hp 2 stroke will be alot thirstier then its v8 in horse power counter part but, the newer efi or 4 stroke ob will get better gas milage then its v8 counter part?

 

[DJ]

Re: Gallons Per Hour

I/O packages are much cheaper to buy.

Fuel economy, probably a toss.

If you have to ask, look at your budget. Multiply it times TWO. In my case, I can't afford either, in your HP range.

Just got done feeding a 7.4L MPI, B-III. Yikes. That combo makes a weekend budget evaporate-FAST.

 

[QC]

Re: Gallons Per Hour

Yeah, I'm with DJ, with modern stuff, we're talking a differnce of $5 a day if that . . .

 

[krisnowicki]

Re: Gallons Per Hour

well very good i have narrowed it down to the 3.0 or 4.3 alpha 1. I have found a 2000 18ft chapparral with the 4.3 and 2002 glastron 18 ft. with a 3.0. I am test driving the both tommorrow. So we will see thanks for your help

 

[Bt Doctur]

Re: Gallons Per Hour

for Example
24 SRV Weekender ,twin IL 6`s, edelbrock 4bbl`s
2500rpm cruise @ 7 1/4 Gal/hr/total
4650, trimmed flat out @ 38Gal/hr /total
It all depends on the boat, load,hull type, pob`s, fuel load, and most of all a GENTLE RIGHT HAND

 

[skeat]

Re: Gallons Per Hour

I have an 18' Four Winns Horizon 4.3 OMC, my friend has a 18' Chapperal with the 3.0 Merc. At best figure 5mpg so at 25 mph thats 5 gph. Those numbers go out the window at WOT where at 45 mph it could be closer to 15+ gph. Compared to my friends boat I cruise at lower rpms at to maintain the same speed, I get on plane quicker (which means popping up water skiiers and wakeboarders easier) and seem to use less gas. I was out the other day just playing around from noon till 6pm and didn't use 10 gallons. (who runs 25 mph all day, I'd be in a different state!) by the time you take a couple of runs towing different things behind the boat, eat lunch, go for a swim etc the day is over and $37 ain't so bad for a day of fun.

 

[Uraijit]

Re: Gallons Per Hour

In my 20' Sea Ray, with carbed 350, I used about 5 gallons in 2.5 hours of tubing/wakeboarding, first time out that it actually ran right . The longer it takes you to get on plane, the more gas you'll use, and this thing gets right up on plane (I just wish it would STAY on plane at sub 20mph speeds).

I'm interested to see how much gas we used in 8 hours of virtually non-stop fun this past Saturday... Haven't filled it back up just yet...

 

[ruf1967]

Re: Gallons Per Hour

Your looking at a range of 3.5 to just over 5 mpg with those power packages mentioned cruising at 3000rpm. Of course ultimately it will depend on the boat's weight and sea/wind/current conditions as well.

 

[HT32BSX115]

Re: Gallons Per Hour

I have an 18' Four Winns Horizon 4.3 OMC, my friend has a 18' Chapperal with the 3.0 Merc. At best figure 5mpg so at 25 mph thats 5 gph. Those numbers go out the window at WOT where at 45 mph it could be closer to 15+ gph. Compared to my friends boat I cruise at lower rpms at to maintain the same speed, I get on plane quicker (which means popping up water skiiers and wakeboarders easier) and seem to use less gas. I was out the other day just playing around from noon till 6pm and didn't use 10 gallons. (who runs 25 mph all day, I'd be in a different state!) by the time you take a couple of runs towing different things behind the boat, eat lunch, go for a swim etc the day is over and $37 ain't so bad for a day of fun.

This is essentially true for just about any engine providing the same power.

I have a Lowrance fuel flow meter on my Liberator. It's a carb'ed 454 and Bravo III.

At 30 mph I burn 10gph. At 45mph it's 15gph.......about 3 mpg at either speed.

Wakeboarding at 20mph is about 7.5gpm

 

[45Auto]

Re: Gallons Per Hour

Do what QC says. Go to BOATTEST.COM (it's free, just give them an email address), look at the TEST RESULTS and do your own research. Yamaha and Mercury also have lots of actual test data for different boats on their sites.

Some people will give you good numbers, some will give you the numbers they want to believe (or tell their wife!). Some people will give you the fuel used in the total hours they were out on the boat, including the time sitting with the engine off listening to the radio and having a few cold ones!

My personal experience, for what's it's worth (agrees with the Boattest and manufacturer sites, which is why I believe them!): 120 HP O/B carbed 2 stroke on an 18' got 2.0 MPG, would do 40 MPH. 120 HP 2.5L I/O in a 16' gets 6 MPG, will do 34 MPH. 425 Hp 8.1L I/O in a 22' gets 3.7 MPG, will do 65 MPH.

Condensed, generalized version of what you'll find:

3.0L go 5-6 MPG, 4.3L are 4.5-5.5 MPG, 5.0L are 4-5 MPG, 5.7L are 3.5-4.5 MPG, big blocks are 3-4 MPG. These figures are at best cruise speed, typically between 25-30 MPH. If you want it in gallons/hour then the 3.0L will drink about 5 GPH, a fuel-injected big block about 8 GPH, with everything else pretty much distributed equally between them.

The boat sizes tend to get bigger as the engine size goes up. 4 stroke outboards are the same as equivalent HP inboards. 2 stroke outboards use twice as much fuel as the equivalent inboard or 4 stroke.

Last thread like this I offered 10:1 odds (I put up $10,000 if he would put up $1000) if a particular poster could run 12 miles (on plane), tow a tube for 2 hours over 15 MPH, then return 12 miles on 6 gallons of gas as he claimed. Couldn't get him to back it up.

I'm willing to make the same 10:1 offer to anyone who is willing to prove that they can pull a tube with a 5.7L (350 CI) at more than 15 MPH for 2.5 hours on 5 gallons of gas. My guess is that the 2.5 hours included a lot of time with the boat not running.

 

[Uraijit]

Re: Gallons Per Hour

I'm willing to make the same 10:1 offer to anyone who is willing to prove that they can pull a tube with a 5.7L (350 CI) at more than 15 MPH for 2.5 hours on 5 gallons of gas. My guess is that the 2.5 hours included a lot of time with the boat not running.

You're right, I'm speaking in terms of PRACTICAL use of boating.

If you're going to be the guy who reckons he's gonna stay on the tube for 2.5 hours straight, you've got a deal! Might want to start training now though, I think about 10 min. is the record for lasting on a tube when I'm behind the helm.

But you also have to figure all of the idling I have to do to go around and pick 'em back up. The boat rarely turns off for more than 2 min. at a time to pick up a skier/boarder/tuber. While the boat it not running on plane full-time, it's pretty much running most of that time.

As I said, that was the first time I had the boat out, and I was simply commenting that I was pleased with how it did on gas--better than I expected. No need to get your panties in a bunch.

 

[45Auto]

Re: Gallons Per Hour

LOL - wouldn't take a bet to stay on a tube behind a 350 for any longer than it takes the boat to come on plane!

I just find it amusing when someone asks about boat performance and gets a reply like "I used about 5 gallons in 2.5 hours of tubing/wakeboarding".

Lots of inexperienced people who don't know any better think that they're going to be able to actually PULL a tube or wakeboard for 2.5 hours after reading a statement like that, based on the questions I get.

No problem with the panties, I'm going commando today if you really want to know!!