Gas Milage

Just started noticing lately how much gas my outboard has been using lately. Not sure if I have a motor issue, or if I just happen to be paying more attention. I have a 1997 100 hp 2+4 Mariner 2 stroke, on a 16.7 Ranger Fisherman. Last time out I went on Lake Michigan for a 4 hour trip from put in to take out, with the majority of the time trolling, on a nice calm evening. I used 9 gallons of gas, and only had 2 gallons left, which gave me some concern when I found out. On the trip before this one I was on the wolf river, and also used more gas than I thought I should have. Anyone have any input, if this is excessive or would be considered normal. If it sounds excessive, any thoughts on what could be causing it.

My Lund says it has a 36 gallon tank and I am sure it is to accomodate my 125 Merc 2+2.  Sure glad the I am not pulling kids on tubes and kneeboards all day long like we used to.  One of these days I will be able to get one of the nice quiet and fuel effecient motors.

I have a 88 yahma 115 v4 she loves the fuel at full throttle... I have had her 22 years and would not change a thing.. I got a 02 t8 and it was the best thing I ever bought... Oil injection 2 stroke and 4 stroke kicker ... I have more hours then I can count on both of them... Great lakes and inland waters now...   I told my son if my boat ever sink's I will go down with her... love my Yamaha motors.. especially the 4 stroke kicker..

By brother has a 2001 115 Merc 2+2 on a Lund 1700 Angler SS and there is a reason his boat has a 27 gallon in-floor fuel tank...cuz you need it! It's no wonder the 2+2 motors were so popular on bass boats. They don't idle particularly smooth and have great hole shot and top end...but those attributes came with a price...fuel costs! He fishes walleye a lot and wishes his boat had a 4 stroke.

I have a 2003 90hp Johnson (carbed, not EFI) on my Princecraft 169. Just got back from Northern Wisconsin vacation this past week. I have a 13 gallon tank in my boat and on 4 fishing outings and taking a family boat ride, I burned 5 gallons of gas all week. That is a 60-degree 4 cylinder that runs on all 4 cylinders whether idling or WOT. It's no 4 stroke, but it's one of the most fuel efficient midrange 2 strokes I've seen. I run synthetic blend XD50 oil and it barely smokes. Used to have a 70hp 3 cylinder Evinrude that wasn't too bad on gas, but smoked a lot more. Basically, those 2+2 Mercs were designed for power / running at higher RPMs and not fuel economy / trolling at lower RPMs. As stated by others in this thread, the only 2 stroke I'd even consider doing any amount of trolling with is an Evinrude ETec, but even then there are better choices, like just about ANY 4 stroke...

I generally don't run a WOT. I usually get the boat on plane, then back off the throttle  by one third. Judging by the posts on here, it sounds like outboards just get crummy gas milage. On the same 9 gallons I used trolling mentioned in my original post, I could drive three hours and go 200 miles at expressway speeds, with my Honda Pilot.

I had a 95 Mariner 115 years ago and that thing sucked the gas, especially at WOT. When I made long runs places like the Mississippi, I could watch the needle on the gas guage go down and my boat had around a 30 gallon tank. 

Back when I had my 84 70 horse Evinrude , I could make two or three trips on Big Cedar from Gornings drive launch to the south and and back and burn through 6 gallons easy at full throttle to half throttle . If that helps 

Unless the two stroke is an E-Tec - then it gets as good or better mpg than a 4-stroke!

Thats a very good thought about the fuel line Brent. I'll have to look at mine closely, or maybe if I run it in the driveway with muff on, I could identify a leak, if there is one. Otherwise I will look next time I am anchored. Maybe of interest to some people, I was told at a dealership that a 4 stroke does get about 1/3 better milage.

Silly question for you, when you shut your motor off and anchor somewhere, by any chance do you notice a little bit of fuel in the water?

I had a similar issue with a mercury XR6 that I had.  The fuel line had a small crack in it, and when the boat was running, fuel would leak out a bit into the bottom of the motor cowling.  When I shut the motor off and anchored, I noticed a little bit of fuel in the water, so I pulled the motor cover off and started it, and found the cracked fuel line. 

It’s very easy to miss if you don’t anchor and just drift or troll. While under power some fuel can leak out, and if you’re not anchored somewhere, you wouldn’t even notice it dripping out of the bottom of the motor cowling. 

you are probably just paying more attention to it, I have a 2005 50HP Merc 2 cycle on a 17.5 mod V boat, it jumps up and goes but really likes the gas too. Getting older so now I just jump it on plane trim it out and putz along about 20-22 mph. I do open it up occasionally because you just should at times (so "they" say). Was really noticeable in Canada where I used to burn through 35-40 gal. in a week

To be honest Tim, I'm usually on local inland lakes that don't need much motoring around, to get to a fishing spot, so I haven't paid much attention to it to compare it to other years. It's not the price that caught my attention, but how fast the tanks emptied. 

I had a couple of the Mercury 125 2+2 motors.  It was a bit of a gas hog in its day.  How much gas do you think you are burning compared to say last month or last year?  Or is it just more noticeable because gas is way up this year?

I have a 1991 16 1/2’ Smokercraft deep-vee with a 40 hp Mariner. I have two six gallon tanks I carry and can burn through most of that fuel if I spend the day on Winnebago reef hopping and/or trolling. Mariner motors from that era were known to be gas hogs. I at one time also had a 1982 15 hp Mariner on a 14’ Jon boat that also was a gas guzzler. Currently have a 2020 Mercury four stroke on a similar size Jon boat and it seams to run forever on a five gallon full tank.