Merc v6 Fuel Consumption

MackAttack · Jun 2, 2004

Re: Merc v6 Fuel Consumption

Interesting thread, but can anyone help me out with my decision? I am looking at 2 boats, same boat (30' Scarab Sport) with the following engine package: ... a) twin 1994 225 carb motors ... b) twin 1997 250 EFI motors

KCLOST · Jun 2, 2004

Re: Merc v6 Fuel Consumption

Mack, I'm a carb guy, so it's hard for me to be impartial... But if I had the choice, those twin 250's would be the way I go... Just because of the power...

LubeDude · Jun 2, 2004

Re: Merc v6 Fuel Consumption

I cant discredit the formula now, as it seems to be the right one. When I originally posted, I seemed to remember another post that for a merc 150 the fuel consumption was in the neighborhood of 4.5 at WOT and about 2.5 at cruising. Evedently I was mistaken. If by that formula, I should be using 15 Gal. per hour at WOT. That would be hard to figure for me as I do not run WOT that much espesially with the price of fuel now. I do not even run close to 7.5 at cruising speed though. I know that I ran at least three hours that day, on a little more than 10 gallons. Thats 3.3 gallons per hour, even if my calculations are wrong, Im still using less than 4. Coming up, I am going to run up the Siusilaw river from Florence to Mapleton and back just for a nice boat ride, about a 22 mile round trip. Ill top off before leaving and do the same when I return, we will see how much fuel I use. Ill probably run at about 20-25 MPH. This is not to discredit the formula, (as Im sure it is right), Just to see what My boat does.

MackAttack · Jun 2, 2004

Re: Merc v6 Fuel Consumption

Called Mercury ... They have specs @ WOT: ... 1) 225 carb @ 5500rpm = 27.85gph ... 2) 250 EFI @ 5750rpm = 28.79gph Buying the 225 carbs (simply rejet for 250hp).

robalofish · Jun 2, 2004

Re: Merc v6 Fuel Consumption

Just to add something to the mix... I have a 1994 200 Carbed. engine WOT @ 5600RPM = 26-27 Gal/Hr Cruise @ 4200-4500 RPM 13-14 GPH So sez my FLOSCAN. Very Accurate.

BW23 · Jun 2, 2004

Re: Merc v6 Fuel Consumption

97 225 EFI on a 23' Whaler, 4000 rpm , 15.8 gph 5400 rpm , 28.3 gph Fuel flow measured with a Std Hzn FF41 fuel flow meter

dajohnson53 · Jun 2, 2004

Re: Merc v6 Fuel Consumption

Originally posted by LubeDude: ...Coming up, I am going to run up the Siusilaw river from Florence to Mapleton and back just for a nice boat ride, about a 22 mile round trip. Ill top off before leaving and do the same when I return, we will see how much fuel I use. Ill probably run at about 20-25 MPH. This is not to discredit the formula, (as Im sure it is right), Just to see what My boat does.

Hey, if you have a GPS, track the mileage and let us know what your mpg is.

dajohnson53 · Jun 2, 2004

Re: Merc v6 Fuel Consumption

Originally posted by MackAttack: Called Mercury ... They have specs @ WOT: ... 1) 225 carb @ 5500rpm = 27.85gph ... 2) 250 EFI @ 5750rpm = 28.79gph Buying the 225 carbs (simply rejet for 250hp).

Why the carbs based on this? Are you thinking the gas mileage is actually better? It looks awfully like a wash to me - I'd have to know what the speed is at the two WOT's and then compare GPH at a consistent speed. My guess would be that if both run at 5500, for instance, the 250's might give a little more speed for the same GPH, and/or very close to identical performance in GPH at a given speed or RPM. Also, I'd rather know what the GPH is at a "typical" cruising speed for that boat or for what you expect to do. For instance, how does the GPH for that speed. And the 250s would give a little more power reserve, it would seem, and maybe better acceleration. I'm also thinking the EFI might give better starting and idling performance. Anyway, I'm not trying to bust your chops, but I can't see why the stats you posted would sway you towards the 225 Carbs when the GPH stat really seems to be a wash and there might be other factors you're thinking about.

achris · Jun 2, 2004

Re: Merc v6 Fuel Consumption

Lube, How close was my 70mph estimate? Chris...........

Dunaruna · Jun 2, 2004

Re: Merc v6 Fuel Consumption

There's not enough differing opinions here, so heres another: EFI (same size engines) will produce a more even and higher torque curve through the rpm range simply because it is far more efficient than carbys (in a well maintained fuel system). HP ratings will also be higher. I don't think the comparative fuel figures at WOT are relevent. EFI will achieve WOT quicker, your driving style will determine MPG. BUT, more things to go wrong, difficult to repair on the water and more expensive parts. With all things concidered - EFI for me, no question. My 2cents worth. By the way, 23ft glass, 302w/280vp - 13.5 mpg at cruise (2800rpm). Navman gps/fuel sensor. Fitted large fin to antivent plate - 12 mpg. No other changes (yet). Aldo

BF · Jun 2, 2004

Re: Merc v6 Fuel Consumption

MackAttack, seems to be more to this decision than only fuel consumption... I wouldn't think the difference in fuel burnt per hour by the 2 rigs would be terribly different. Maybe a bit... but what about other things? How many hours on the motors?? The 3 year newer ones have considerably less? How much price difference? Would you be paying a LOT more for newer/EFI engines? Either come with warranty or after sales support of some kind? Do you have the maintenance records for either rig? You get the picture... a couple gallons per hour seems like a fairly minor point to me. But then I'm not an "offshore" kinda guy either, so maybe I'm off base. Hope this helps. Brent

LubeDude · Jun 2, 2004

Re: Merc v6 Fuel Consumption

Originally posted by achris60: Lube, How close was my 70mph estimate? Chris...........

It will run 65+ MPH with a 27P 14.25" four blade Turbo prop. Im running a 25P High Five now as I like the bite better, but it runs 63+ MPH. I just bought a GPS on Ebay today, so I should have it by the time I go on the river trip. Wife came down with a cold today, so it will be a while.

MackAttack · Jun 2, 2004

Re: Merc v6 Fuel Consumption

Thanks for input. My issue is that it is 70 miles to the Gulf Stream here, and ususlly choppy. So top speed isn't of primary importance. I need reliability (and "fixability" + decent fuel consumption. In a perfect world, EFI is better and prob has better mpg at the lower RPMs (WOT is pretty poor comparison from Merc)., but its a long ride home if a module blows, etc. The carbs are more straight forward. If money were no object I would go with the Optimax (best power/weight + great gas mileage), but still more complex. The Verado is new and cool, but unproven as yet, so it would NOT be my 1st choice if cost wasn't a concern. It took Merc 3-4 years to get the Optimax ironed out for example ... Thanks again for the input!

achris · Jun 2, 2004

Re: Merc v6 Fuel Consumption

Just to throw another angle on the reliability issue. Merc have been running EFI for over 10 years now and have the bugs pretty well iron out. I have seen very few with problems in the fuel system. The most common fix for them is, beleive it or not, cleaning the battery terminals. Like all electronics, it gets a bit jumpy with dirty power. Doesn't kill them, or even stop them running, just gives the wierdest symptoms. Chris..........

MackAttack · Jun 4, 2004

Re: Merc v6 Fuel Consumption

Thanks again for the update. Looks like the EFIs will win by default - the 225 carb boat doesn't have title onthe motors, and South Carolina requires title. Digging deeper revaled thatthe owner has notitle in the state he lives in for the boat and no titles at ALL for the motor. Punt. The 250 EFIs will be fine - probably better gas mileage at slower speeds, and easier to start! (Hope this guys has titles).

Merc v6 Fuel Consumption

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