Probably normal but this boat sucks down gas quick

[Robertpel9]

I am loving having a boat. When i picked up my like new 1995 Chris Craft Concept 18 with the VP 4.3GS in early May it only had 89 hours on it. I now have 133 already.

Why does it use so much gas though. It seems that everytime i take it out i use 1/4 tank and that is only about 40 minutes of actual driving. I run it at 3000 RPM trimmed out nicely and it runs smooth as a top. I keep the underside clean as a whistle. I would think it would get better gas mileage. Is it even worse with the 5.0 and 5.7's

Does this kind of consumption seem abnormal? At near 5 bucks a gallon at the lakeside pumps i want to make sure i am not missing something here

 

[marine4003]

Re: Probably normal but this boat sucks down gas quick

Welcome to the wonderful world of boating....yup,thats about it for GPH I/O Marine engines are very inefficient machines,half the energy generated by these motors gets sloughed off as heat,want good fuel economy ?? get a 4 stroke outboard..otherwise..join the money-pit-owners

 

[DRIFTER_016]

Re: Probably normal but this boat sucks down gas quick

Or if you really want good mileage get one of them Blow Boats, you know the ones that hang their laundry out to dry when they're out on the lake.

 

[tashasdaddy]

Re: Probably normal but this boat sucks down gas quick

actually that is good consumption, outboards average 1 gallon per hour for every 10 hp. you have around 190 hp. which would come out to 19+- gallons per hour. inboard/outboard have a better fuel rating, but higher maintenance cost.

 

[salmonee]

Re: Probably normal but this boat sucks down gas quick

I'm in the market for an 18-19' boat and may have to look for one with an outboard. I was just a yamaha's website and their 90hp 4 stroke outboard gets like 6mi/gal cruising a 17.5 boat at 3000rpm ~20+mph. My problem is that not many runabout comes with an outboard. Glastron is the only one that comes to mind with an outboard.

 

[tashasdaddy]

Re: Probably normal but this boat sucks down gas quick

salmonee, don't know where you are getting your info. but there are many outboard runabouts available.

 

[Phantom_II]

Re: Probably normal but this boat sucks down gas quick

actually that is good consumption, outboards average 1 gallon per hour for every 10 hp. you have around 190 hp. which would come out to 19+- gallons per hour. inboard/outboard have a better fuel rating, but higher maintenance cost.

Those figures just don't seem right. I have a 17.5 foot boat with the same engine (except the paperwork claims it's 230 HP) and I can spend 4-5 hours pulling people around on tubes using less than 20 gallons of gas.
Maybe at WOT I might see those numbers but for the most part I run between 3000 and 3500 rpm while towing.

 

[204 Escape]

Re: Probably normal but this boat sucks down gas quick

Maybe the "GS" after the 4.3 stands for Gas Sucker !!!! LOL

(Sorry, I couldn't pass that up)

 

[Robertpel9]

Re: Probably normal but this boat sucks down gas quick

It i shard to measure i guess as i am saying i use about 1/4 tank wvwey weekend when i go out which is about 40 minutes. What i don't know is if it is like a car where the gauge going down is not linear.

My best reference point is that i had 1/8 of a tank 2 weeks ago this past friday. I put 75 bucks of gas in at 4.80 a gallon. it took me to a little over 1/2. I drove about an hour or so that weekend then the next week i drove 20 minutes back to the restaurant / marina where i go for friday happy hour and put another 75 bucks in, that took it to just over 3/4. I have driven maybe 2.5-2 hours since then and i am down to 1/4 now. Not very scientific but lets just say when i am crusing around i can look down in 20 minutes and see the fuel gauge has moved noticibly

 

[xxxflhrci]

Re: Probably normal but this boat sucks down gas quick

actually that is good consumption, outboards average 1 gallon per hour for every 10 hp. you have around 190 hp. which would come out to 19+- gallons per hour. inboard/outboard have a better fuel rating, but higher maintenance cost.

Yep, we have had a couple of outboards, one 85 hp and one 95 hp. Both of them used more gas than my 140 I/O. Personally, I don't find I/O maintenance to be a big deal.

 

[erlindbl]

Re: Probably normal but this boat sucks down gas quick

salmonee... I agree, as far as new boats go it is very difficult to find runabouts with an outboard. Glastron and Tahoe make them, but I saw a Tahoe thread on here that would make me nervous. I bought a Glastron GT 180 with a 150 E-tec. It's amazing for pulling power and top end but the DI two strokes are about the same as the I/Os on gas. A full day of waterskiing and wake boarding will cost me 12 to 15 gallons. For cruising I went 54 miles up lake Mojave at 30 MPH using 9 gallons (6 mi per gallon) and came back down at 40 MPH using 12 gallons (4.5 mi per gallon).

At $5.00 a gallon it isn't cheap but I wouldn't do it any other way. The boat is awesome.....

 

[dingbat]

Re: Probably normal but this boat sucks down gas quick

I bought a Glastron GT 180 with a 150 E-tec. It's amazing for pulling power and top end but the DI two strokes are about the same as the I/Os on gas.

Welcome to 21st century outboard technology.

HP to HP a DFI 2 stroke or 4 stroke outboard should get the same if not better fuel economy that an I/O.

 

[cmcpherson]

Re: Probably normal but this boat sucks down gas quick

It i shard to measure i guess as i am saying i use about 1/4 tank wvwey weekend when i go out which is about 40 minutes. What i don't know is if it is like a car where the gauge going down is not linear.

My best reference point is that i had 1/8 of a tank 2 weeks ago this past friday. I put 75 bucks of gas in at 4.80 a gallon. it took me to a little over 1/2. I drove about an hour or so that weekend then the next week i drove 20 minutes back to the restaurant / marina where i go for friday happy hour and put another 75 bucks in, that took it to just over 3/4. I have driven maybe 2.5-2 hours since then and i am down to 1/4 now. Not very scientific but lets just say when i am crusing around i can look down in 20 minutes and see the fuel gauge has moved noticibly

You have got to fill the tank to be able to make any reasonable assesment.

 

[QC]

Re: Probably normal but this boat sucks down gas quick

Agree ^^^^.

The 19 GPH that TD suggests above is at WOT aka rated horsepower. Boat size, weight, bottom type and speed make the biggest differences, not engine technology. Boats are inneficient, not most engines . . . It's also not OBs, or I/Os, but technology. Two cycle carbed OBs are horrible on fuel, Jet drives with big V8s are bad. Newer jets with modern engines are better, modern EFI and DFI OBs are good. I/Os are heavier, hence sometimes OBs do slightly better.

 

[45Auto]

Re: Probably normal but this boat sucks down gas quick

I love these gas mileage threads! There?s lots of real data out there on the boat magazine and manufacturer websites. Lots of posts here also from people with fuel flow meters and GPS speedometers who can give you real numbers. Unfortunately lots of people WITHOUT instruments like to fool themselves on how good they think their gas mileage is!

Your gas mileage sounds about normal. Boats SUCK when it comes to gas mileage. A 17 or 18 foot fiberglass runabout with a decent 4-stroke engine (inboard OR outboard, makes no difference) is going to get right around 5 MPG (which means its burning 5 gallons per hour) at best cruise speed in a lightly loaded condition. A 2-stroke (E-TEC included) will burn about twice as much fuel.

Since you are not at optimum cruise speed all the time your engine is running (accelerating and running at other than optimum cruise really sucks down the gas) you are probably easily using 12 ? 15 gallons ($60 - $75 at $5 a gallon) in a couple of hours IF the boat is running that whole time.

These tests of 18? boats show about what you can expect:

V6 Inboard from Boattest.Com:

Fuel Injected 4-stroke Outboard from Yamaha website:

As you can see, at best cruise speed you?ll get just over 5 MPG if you?re lucky (remember, these are lightly loaded boats ? no extra people, coolers, etc).

This means you?re burning about 5 gallons per hour minimum while the boat is running on plane. When you?re accelerating or running at faster or slower speeds you?re getting WORSE mileage, so your average will be about 3.5 to 4 MPG.

We had this discussion in an earlier thread, this data from Four Winns gives the performance of the same boat (17? Horizon) with 5 different motors:

http://assets3.fourwinnsmarketing.co...X (p2-5).pdf

Here it is in a graph so it?s easier to talk about:

As you can see, the 135 HP 4 cylinder I/O (3.0), 190 HP V6 I/O (4.3), and 90 HP outboard all burn about 5 GPH at 25 MPH. This magically works out to about 5 MPG!!!!

If you want to double your fuel consumption go with one of the higher HP E-TECS.

Those figures just don't seem right. I have a 17.5 foot boat with the same engine (except the paperwork claims it's 230 HP) and I can spend 4-5 hours pulling people around on tubes using less than 20 gallons of gas.

It costs my boat about 10% in gas mileage to pull a tube. So an 18? towing at 25 MPH will probably burn at least 6 GPH. If your tubing is like most people, then at least an hour of that 4 hours of tubing is probably with the motor stopped, talking, changing tubers, etc. Probably more like 3 hours of actual tube towing time. So 4 hours of tubing (really 3 hours running at about 6 GPH, 1 hour loading tubes, etc) would burn 18 gallons of gas. In other words, you?re getting the same fuel consumption as RobertPel9.

If you?re really interested in fuel consumption, get one of these:

http://www.iboats.com/LowranceNET_L...4833551--**********.489590275--view_id.359411

and a GPS.

Then you can compare your fuel consumption with verified data and you won?t have to guess at how much fuel you?re using!

 

[Fu-Inator]

Re: Probably normal but this boat sucks down gas quick

Good info 45Auto! I guess I'm a little more simple in my gas planning. We pretty much have a routine now; hit lake around 10am, tube for 2 hours, eat lunch on beach 1-2 hours, tube for 2 more hours, go home. Usually use half a tank, 10-12 gallons. Wash and repeat the next weekend.

 

[Robertpel9]

Re: Probably normal but this boat sucks down gas quick

How do you know if you have the right air / fuel mix. I do not have a lot of experience with Carb'ed engines. My engine runs smooth as silk and fires right up after sitting for a week etc so i know if cannot be too bad off. At the same time when i am going really slow especially in reverse i can smeel heavy gas aroma.


Anyway are those smells normal and how do you know if you have the engine tuned for maximum fuel efficiency

 

[QC]

Re: Probably normal but this boat sucks down gas quick

Thanks 45 dude, I was going to look for those threads and crosslink. You're da man, imagine that, data . . .

Like you, I love these fuel economy threads. Throw in some horsepower and torque discussion and then us engine dudes are in stupidity heaven These almost all boil down to horsepower to weight, and then add in some bottom efficiency stuff. Modern engine manufacturers could not stay in business if they weren't comparable in fuel use. That being said, there are definitely combos that are better.

What I love most about that Horizon data is that it illustrates some things that are discussed here (and misunderstood) quite often: OB speed vs. I/Os (the 90 vs. the 3.0 is interesting). Fuel economy vs. horsepower. OB vs. I/O period. And also how much horsepower is required to achieve higher speeds. Lot's of nuggets there for miners willing to dig a little!

Edit: BTW, "stupidity heaven" was referring to those of us who waste an unimaginable amount of time compiling data and trying to get our heads around it. Not referring to those of you who ask these great questions . . .

 

[45Auto]

Re: Probably normal but this boat sucks down gas quick

From QC:

those of us who waste an unimaginable amount of time compiling data and trying to get our heads around it.

Kind of scary QC!!! You're getting to know me too well!!!!