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Author Topic:   Merc 115 four stroke fuel consumption
13DAUNTLESS posted 11-11-2003 01:02 PM ET (US)   Profile for 13DAUNTLESS   Send Email to 13DAUNTLESS  
How much fuel are the 115 4s Mercs burning?
Bigshot posted 11-11-2003 01:42 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Depends on how fast you are going. To give a comparison, my buds 115 suzuki burns about 4-5gph at cruise(4k+/-). My 70 burns 2-3.
13DAUNTLESS posted 11-11-2003 03:12 PM ET (US)     Profile for 13DAUNTLESS  Send Email to 13DAUNTLESS     
Being more specific I was wondering what the 115 4s burns at cruise as well as WOT and if anyone has the specs at all RPM ranges that too would be great.
jimh posted 11-11-2003 10:20 PM ET (US)     Profile for jimh  Send Email to jimh     
As I have previously mentioned, it is really unfortunate that the Mercury Marine website does not have more information available about field tests of their engines with various boat. You can get a sense of the fuel consumption for the 115-HP 4-stroke engine from the Yamaha website. They have many field test reports

Try this hyperlink to get started:

There are many reports with the 115-HP on various types of boats. These ought to give you some useful information.

Marlin posted 11-12-2003 03:28 PM ET (US)     Profile for Marlin  Send Email to Marlin     
While I can't give specific fuel consumption rates at different RPMs, I can give you my overall impression of the 115-4S consumption on my 160 Dauntless. I've had the boat one season now, and have put about 70 hours on it. That time is over a mix of speeds, but I typically cruise at between 3300 and 3800 RPM. Usage is mostly "pleasure cruising", with some tubing. The engine has been run at WOT for no more than a few minutes. Overall, my average fuel consumption is about 2.2 gal/hr. Wow.
Bigshot posted 11-12-2003 04:01 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
That is average and you can't use that too well. If you set out for a long offshore run thinking you will avg 2.2 you will run out of fuel real quick.

My 70 4s avgs between 1-1.5gph per tank, she burns about 2-3 at cruise and probably 6+ at WOT. My 225 burns about 12-13gph at cruise/ 23 @ WOT but avgs about 7-8 per tank.

Marlin posted 11-13-2003 05:57 PM ET (US)     Profile for Marlin  Send Email to Marlin     
Bigshot, I agree completely. But that overall average is all I have, and I figured it was better information than nothing.
13DAUNTLESS posted 11-13-2003 06:14 PM ET (US)     Profile for 13DAUNTLESS  Send Email to 13DAUNTLESS     
Thank you all for your info. I have found from talking with Merc and Yamaha that It should burn between 4&5 gal/hr at 4000 to 4500 rpm depending on the weight of the boat.
Thanks again,
Tom2697 posted 11-14-2003 10:15 AM ET (US)     Profile for Tom2697  Send Email to Tom2697     
A VERY rough estimation is to divide your horsepower rating by 10 for WOT and then take the percentage of rpm that you are running from WOT for this number.

For example, Bigshot's 70hp will burn about 7gph at WOT and @ 3000rpm (about 55% of WOT), he will burn about 3.85gph. His numbers are much better but this will throw in some safety for you. Then, also use the 1/3 rule for planning a trip. Use 1/3 of your gas to get there and 1/3 to get back, but save 1/3 for safety and DO NOT plan to use it.

Bigshot posted 11-14-2003 01:25 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Tom that is a great way to tell fuel consumption on conventional 2 smokes. The curve is way different with DFI and 4 strokes.

Like my 1st post said...about 4-5gph at cruise on my buds 115 Suzukis. 2 sroke 115's would burn about 6-7gph and unfortuantely so did my 88spl.

Tom2697 posted 11-14-2003 01:30 PM ET (US)     Profile for Tom2697  Send Email to Tom2697     
Aren't 4-strokes great?!?!?

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