Mecury EFI Fuel Economy

[srq_fl]

I recently aquired 25 ft walk-around cudy with Mercury 250 EFI (1995 with less than 150 hrs). The engine is burning about 22 gallons per hour @ 30MPH at 4200 rpm. A freind of mine with a similar boat with 1999 Optimax 225 only burns 5 gallons per hour under the same conditions.<br /><br />Is the fuel economy on the EFY that much more than the Optimax (400% more) or is there something wrong with my 250 EFI?<br /><br />Any feedback or possible fixes would be appreciated.

 

[Kenny Bush]

Re: Mecury EFI Fuel Economy

Something is wrong. You need to clean that 250 up and check her out. The economy depends on your drive speed. The Opti's (DFI)tend to do better at low, constant cruising speeds, but the EFI's will be a little more reliable under hard use. The opti's will give you better economy, until one of those many sensors picks up something. The Opti's seem to fail with more damage. I think the DFI is more cosmic in regards to oiling, which may lead to more damage when it fails.

 

[mjbrueck]

Re: Mecury EFI Fuel Economy

If I were you, I'd offer to always take his boat and you'll pay for the gas based on his 5 gph (he can pay to top off the tank after that). I'd guess with a 4000+- pound boat and the Optimax, he's getting more like 2-2.5 mpg (12 -15 gph). Either his fuel flow sensor is on the fritz or he's exaggerating.<br /><br />Your boat sounds about right. We had a 20' WAC with a 150 2-cycle and averaged around 2 mpg at cruise.

 

[Kiekhaeferscurse]

Re: Mecury EFI Fuel Economy

Sure to cause some argueing here with this one but over the years it seems to me the answer is:<br />WOT 10 hp=1 gph<br />WOT 100 hp= 10 gph<br />WOT 1000 hp= 100 gph<br />4 stroke 2 stroke, diezel, rotary etc etc<br />Yes the new 4strokes opti's etc all use less fuel on startup, idle & some even at midrange, but when it comes right down to it to make power ya gotta burn the fuel.

 

[srq_fl]

Re: Mecury EFI Fuel Economy

Thanks for all responses. Still I don't know why the 1999 Optimax 225 is burning 2/3 less gas that the EFI 250 on similar boats and same water conditions. Both boat have engines mounted on transom brakets. (we go out 90 mile offshore fishing, EFI uses ~66 gals and Optimax uses ~22 gals fuel). <br /><br />Would reducing the size of the prop help. EFI runs WOT @5100 rmp at 42MPH.<br /><br />EFI engine smokes a lot when first start, the Optimax does not. Are there anything on the EFI to tune to make it run leaner/reacher in order to improve efficency?

 

[KCLOST]

Re: Mecury EFI Fuel Economy

Prop size depends on slip, and WOT rpms that you can reach.... 5100 rpms,,,, is that within the WOT range specked for the motor... Just remember that higher rpms = more fuel being burned and if that's caused by a lower pitch prop normally you'll get less speed at the same rpm...<br /><br />250hp/10 = 25 gph at WOT<br /><br />I think your buddy is full of it, there ain't a 225 motor out there that will run 5 gph at near WOT.

 

[Opti-missed]

Re: Mecury EFI Fuel Economy

theres no way hes burning 5gph with a 99 opti 225. mine burn 13 gph each and plenty of oil. 22 gph on a single screw? ouch.

 

[Opti-missed]

Re: Mecury EFI Fuel Economy

lets see thats 180 miles rnd trip at 30 mph @4200 rpm as stated in your post. thats 6 hrs round trip. 66 gallons divided by 6 hrs. thats 11 gph my friend and 2.7 mpg. cant beat that with a canoe. like i said, theres no way your buddy is burning 5 gph at the stated rpm and speed.

 

[gss036]

Re: Mecury EFI Fuel Economy

I have heard that the 250 likes gas, so I go along w/opti-missed, 11 gph/ 2.7 mpg is pretty good. That's about all I can squeeze out of my 200 on a good day on my SeaCraft 23WA. I have a friend that has a new 225 Opti-maz on his 23-24 Whaler and he told me he was getting about 8 gph @ 4200-4400, which sounds about right.<br />If your friends boat is that good, go with him pay for his gas. :-}

 

[srq_fl]

Re: Mecury EFI Fuel Economy

Opti-missed:- the 90 mile trip metion earlier is round trip burning 66 gal= 1.36 MPG at average speed of 30 MPH= 22 GPH at 4200 rpm.<br /><br />Yesterday, I tried a smaller diameter prop, same pitch (13 3/4 by P17). This increased WOT rpm to 5800 rpm which with the same top end speed as the original bigger diameter prop. I do not know yet how the smaller prop affects the MPG or the GPH.<br /><br />I also would like to know if there is anything on the engine that can be tuned to optimize fuel efficency. <br /><br />Thanks for all feedbacks and comments.

 

[Opti-missed]

Re: Mecury EFI Fuel Economy

srq_fl,<br />not sure what to tell u. im not an expert on tuning 2 strokes or propping them. the numbers just seemed really screwy. maybe call a high performance prop shop and talk to somebody who really knows props. have u spoken to someone at merc. ask for an applications engineer and tell'em what youve got. it may be normal for that motor hence all the crazy claims about the efficiency of the optimax. good luck!

 

[gss036]

Re: Mecury EFI Fuel Economy

I would think that the 13 3/4 X17 is a bit small,think about a 14 1/2 X 17 cupped prop. That would get your RPMS back down a litte bit and give you better control when trimmed out to max as it will hold the water better. There is definatley something going on use 22 GPH at 4200. I would have expected about 15 GPH and 22 at WOT.

 

[Kiekhaeferscurse]

Re: Mecury EFI Fuel Economy

Bottom of your boat clean?

 

[BW23]

Re: Mecury EFI Fuel Economy

My 97 225 EFI burns 15 gph at 4000 rpm on a 23'Whaler. WOT bout 23-24.