Fuel Consumption vs. Cruising speed/rpm

Willhound

Getting closer to sea trial/delivery of our "new to us" 2000 FV270 with Mercruiser 5.7L EFI with stock BIII drive. Curious of real world examples of what to expect for fuel consumption vs. a reasonable cruising speed. To me, reasonable means on plane with just enough throttle and tab in to keep it there. For example, with two people aboard, half a tank of fuel and water tank topped up, what RPM/Speed/GPH should I be looking at. Searched several different ways on this forum, and few others, and although there are a few charts and that animated fuel consumption website, I don't see how they relate to a particular hull, weight etc.
Is there a chart or something someplace that I missed? Any anecdotal examples?

diggin2day1

My VesselView says that I'm getting 12.6gph while cruising at 28mph at 3500rpm. FV270 with 350 horizon and Bravo 3... 22p props. 

Willhound

So after 3 full seasons I'm reviving this thread to somewhat answer my own question.
I never could find a fuel graph for a 2000 Era FV270 with 5.7L EFI Gen+ but for the last 3 years I've tracked my fuel consumption and hours. My engine isn't VV compatible or I'd have it and I don't have a fuel flow meter. These numbers are an average of all hours run, so everything from idling at the dock to full burn. But most of the time I'm on plane at between 3400RPM/24mph and 3600RPM/27mph where the engine seems happiest and I can easily stay on plane with 2 to 3 adults, full fuel and water and gear. My "seat of the pants" makes me think that this is likely the sweet spot for max GPHvsMPH although I'd be happy to be proven wrong. I have been toying with the idea of running at another 200 RPM or so higher the next couple of tanks to see if it makes a difference better or worse.
My average over the 3 years has been 23.54 LPH or 6.22GPH. Wherever you see Gallons in the attached I've converted to USG, not Imperial. USD figures were converted using an average exchange rate over the last 3 years of $1.30CDN to $1USD. Average fuel cost per hour of $32.55 CDN or $24.54 USD. The first row entry is from the day we picked up the boat and filled it on the way to the lake. That fuel is not included in the averages.
I fill to full every fill up. For better or worse I don't believe in running around half empty and filling up around here is often a hassle so when I fill, I fill.
For all you numbers junkies out there like me.

diggin2day1

Here's a big thread on this exact subject... 
http://rinkerboats.vanillaforums.com/discussion/4295/2005-270fv-cruising-speed-rpms-etc

Handymans342

Dont get me started LOL

Stodge

Take a peek here:  http://www.boat-fuel-economy.com/mercury-mercruiser-350-magnum-5.7-fuel-consumption-us-gallons

LaRea

From the perspective of fuel consumption, there's not much incentive to keep a slow cruise speed.  You can probably cruise just about any speed you want and the MPG won't vary more than 15% from optimum.  

For example, boattest.com tested a 270 with the 6.2 and found that she could cruise anywhere from 23 to 34 MPH without losing more than 15% compared to the "best MPG" speed of 27 MPH.

Most Rinker express cruisers are like that.  Once you are on plane, the fuel consumption stays pretty flat until you get near wide-open throttle.  

Willhound

Oh boy...okay, I'm a "new guy" here, and really not trying to open a can of worms. I realize that the debate can go on all day regarding different set ups, weight distribution etc. D2D1, as I mentioned,  I did several searches on this forum and elsewhere. That thread was one of the first to come up. It gives one real world example, for a different engine (Volvo DP) and then quickly sidetracks into a discussion about whiskey and a bikini shot of somebody on a beach. (nice shot though!). Stodge, I appreciate the link. Been all over that. And I'm sure it's pretty good, but doesn't refer to specific models, just the engine, presumably on an engine stand somewhere. LaRea, that does give a good example, and the Boat test article you mention is exactly the kind of thing I was searching for, but for my engine set up. That's what's confusing me. Every boat magazine test article I've ever seen usually has a chart showing RPM/Speed/GPH. The FV270 has been such a popular model over the years I'm baffled as to why I can't find anything in any of the archives. Was that engine such a dog that nobody bothered to test it? I realize all the manufacturers likely supply the media with the "upgraded" models so they show the product in the best possible light.
But does no one own, or have owned that series FV270 with the 5.7 EFI 260 hp that can say, "I found that at around xxxRPM and XXXspeed I was averaging around xxxGPH? Although I'll be new to cruising, every boat I've ever owned had that certain speed/RPM where the ride was comfortable and the GPH was about the best it was going to get, for that speed. Obviously the best GPH any boat will ever get is either sitting at the marina, or at idle, that's not what I'm talking about. But in the real wold that information I'm trying to find must exist, just can't seem to find it. I'll keep looking.

J3ff

I'm not sure if it's accurate, but the vessel view app on my phone stays on 1 mpg  up on plane... hopefully that isn't right?  

Stodge

@J3ff I get that in the 342. I see 1.1 to 1.2 in ideal conditions.   A 270 should be seeing more like 1.5 to 2.0 MPG I would think.  My old 280 with twin 4.3L used to get 1.5 on a good day.

Willhound

Ahhh...diggin2day1, that is exactly what I was hoping for. Thanks a bunch. If I may ask, and as per LaRea's example, do you find fuel consumption any much better or worse at a slightly slower speed, say around 20 or 24 mph?  Will it hold on plane at 20 or what is the minimum reasonable speed on step on an average day?

Handymans342

If you need to worry about fuel consumption then you don't need to own a boat

Stodge

@Willhound if it's like my previous or current Rinker it's tough to stay on plane at 20MPH.  I can do with with the tabs in.  25-28 is my typical cruise speed.  In my old 280 is was 26-30.

diggin2day1

I agree with Stodge... I can probably get it down to about 24mph, but it's a constant struggle to stay on plane(and honestly not worth it). I am usually burning between 12.5 to 14gph, but if I start to push the throttle it easily rises to 22+gph.  That's also the beauty of the VesselView, I can actually watch my GPH change as I adjust my trim and trim tabs... helps me find the "sweet spot" on long trips. 

Willhound

Handymans342 said:

If you need to worry about fuel consumption then you don't need to own a boat

Thank you for your concern for my financial well being......but that's not the point. I'm the kind of guy that needs to know details. And yes I do need to worry about fuel consumption as some of the areas we will be operating in the fuel stops are sometimes  a distance.

Willhound

Thanks Stodge and Diggin.  Good insight. Super stoked for the new boat and just really like to get a feel for what to expect and it'll give me an idea of what I should be looking for during the sea trial. 

Handymans342

Willhound said:

Handymans342 said:

If you need to worry about fuel consumption then you don't need to own a boat

Thank you for your concern for my financial well being......but that's not the point. I'm the kind of guy that needs to know details. And yes I do need to worry about fuel consumption as some of the areas we will be operating in the fuel stops are sometimes  a distance.

Good point!

russellh

This is useful.......
i own a 270 with a 5.7 GXI
http://www.boat-fuel-economy.com/volvo-penta-3.0-gl-135-fuel-consumption-us-gallons

planesailing

I have the 5.7 efi with bravo 3 in my 242fv. I find my best cruising settings are 3500 rpm which gets me to about 28-30 mph and returns about 1.4mpg. WOT is around 4200 rpm which gets me to about 35+mph but then delivers about 1 mpg. I have the 24p props. Hope this helps.

Willhound

All good stuff, thanks folks. Gives me a good "real world" feel for what to expect. If I can manage 12.5 - 13 GPH at around 25-28MPH, a full tank should give me a safe range of around 6 hours or 150 miles or so, keeping a little over an hour's worth of fuel as a safety margin, which is plenty for where I need to go. Or 3 hours out and 3 hours back in Georgian Bay.
Cheers!

diggin2day1

I just checked my records and I went 105 miles to Block Island in August and used 56 gallons of fuel. Approximately 85% of the trip was cruising on plane in a calm ocean. 

randy56

Seems the slowest I can go is 26 mph and still stay on plane, with the 4x3 21p props. 

Handymans342

Willhound said:

All good stuff, thanks folks. Gives me a good "real world" feel for what to expect. If I can manage 12.5 - 13 GPH at around 25-28MPH, a full tank should give me a safe range of around 6 hours or 150 miles or so, keeping a little over an hour's worth of fuel as a safety margin, which is plenty for where I need to go. Or 3 hours out and 3 hours back in Georgian Bay.
Cheers!


So if my math is correct thats $52 an hour at $4 a gallon. 

randy56

$52 per hour, boating is such a wise investment. LOL

Willhound

randy56 said:

$52 per hour, boating is such a wise investment. LOL

I wish. That would be cheap. One American gallon = 3.78 Litres. Good Ethanol free marine gas here sells for $1.40/L CDN on the water. Marina's will not allow Jerry cans. Convert to USD at 1.35 CDN for 1 USD = $7.14 USD/Gallon x 13 GPH = $92.87/HR!
Partly why we kinda worry about fuel consumption here...

Handymans342

How much is diesel up there?

Willhound

Diesel would be roughly equivalent since my example used premium gas and on the street diesel and premium are priced about the same. Harder to find on the water though. A few of the bigger marinas have it, I can think of two off the top of my head, on Lake Simcoe where my home marina is.

Handymans342

Alswagg said:

I just bought 30 gal of diesel. $2.08 gallon for pre tax marine aka off road.  

Yeah but thats not at a marina

J3ff

Maybe I missed it, but do we have any concrete numbers for gallons per hour at certain rpm's for the regular gas mercruiser 350 or 383?  The boat test one is a diesel engine right? 

Willhound

  

Alswagg said:

I just bought 30 gal of diesel. $2.08 gallon for pre tax marine aka off road.  

Yeah but thats not at a marina

And in USD.  The Admiral and I head to sunny Florida next week for our annual visit and although my American friends may not agree, I always laugh at how inexpensive gas is, even taking into account a 35 cent premium on the dollar for exchange. Between ethanol subsidies on the US side, and the gas taxes we get hosed for on the CDN side, we pay substantially more for fuel on this side of the border, dollar to dollar. Whether in Litres or Gallons, about 60% of the cost goes to the government, 35-37% to the producer/distributor and about 3-5% to the local dealer.

Willhound

J3ff said:

Maybe I missed it, but do we have any concrete numbers for gallons per hour at certain rpm's for the regular gas mercruiser 350 or 383?  The boat test one is a diesel engine right? 

That's a very concise way of asking the original question I asked in my first long winded post. 

Handymans342

Willhound, where in FL are you headed? Also remember that all those tax dollars goes to subsidies like your health system.