75 mercury fuel consumption

[bowhunternw]

I have a 2001 75 that is new to me an seems to use fuel at an alarming rate. It also seems very cold blooded and likes to die at idle. I read something about possible sticking carb floats. Is there a way to test them or any ideas out there?

[trolloni]

had a classic 50 the salesman told me itll run smoother than a 2 cylinder cause it has 4 cylinders ,he didnt tell me it would wolf down two 6 gal tanks a day,it went real quik right to the used motor aisle !

[20lbSloughShark]

It might just be that the motor does not idle that low. I found this out on my 40 hp Johnson. I would say at full throttle mine burns about 1 gallon of gas per hour maybe a bit more. Back off to about 3/4 throttle and you will burn just over half that amount. If yours has 3 cylinders it is probably similar to mine. I have got comments that mine is "the best running big twin i've seen", but I think its junk. I idle at 1000 rpms, and that's rough. I don't care what people say about how johnson and evinrude are the same thing, I think the ones that start on the first pull are painted blue.

If I could have any motor in the whole world, it would be an evinrude e-tec.

[bowhunternw]

It just seems to me like it is running rich, and can burn a tank of fuel real easy in a day, without running it that much or very hard. Maybe it is just the nature of that engine but just seems like something is wrong with it to me. Thought maybe someone out there had a similar experience

[clKiekhafer]

A good rule of thumb on has consumption is take the hp (in your case 40) and divide it by 10 this would then be the approximately number of gas per hour you would use at WOT. So in your case that would be 4 gph. I found this to be very true with my last two boat. I had a 150hp Evinrude that was thirsty and it was in that 15gph range. I ;than traded that boat/motor and got a 150hp Yamaha 4-stroke and I at WOT that also uses about 15gph, but it use much less at half throttle then the 2-stroke.

[wmw]

it may need to have the carbs cleaned but if your using 6 gallon cans it will use gas at what seems like a alarming rate. always have 2 gas cans

[Crow Hunter]

I have a Mariner 75 and it is rather thirsty also. as for being cold blooded and dying at idle- I had the same problem, and I found the cause. It has the type of fuel filter that you can take apart to replace or clean the screen; it was not tightened properly, so it was losing pressure there. Once I tightened it up everything got much better. Something to check if you have this type of filter.

[marine_man]

What boat is this motor on? In general, Merc 75hp motors from that era were cold blooded, but pretty much bullet proof.

marine_man

[bowhunternw]

What boat is this motor on? In general, Merc 75hp motors from that era were cold blooded, but pretty much bullet proof.

marine_man

It is on a 16' mr. pike same year. I would say that it is getting around 2 miles to the gallon. And it is a real bear to get it warmed up enough to actually idle when first getting to the lake. Once warm it still has some trouble idling. I will hopefully have some time here to work on it a little. Gonna try to check the fuel filter, also read something about the thermostat stuck open and hoping to get some more ideas.

[20lbSloughShark]

2 mpg is very good for an outboard

[delcecchi]

That boat and motor should be getting at least 4 mpg. At 3/4 throttle it will go like 30 mph and be using like 4-5 gph. That would be like 6 mpg.

No Prius for sure.

[Kyhl]

2mpg is good on a 75hp?

I guess if it is mounted on a house boat.

My last 90hp carbed 2-stroke ran 3mpg at WOT on a 16" fiberglass boat.

My current 115 4-stroke gets at least 3mpg at WOT on an 18" tin boat, and 5+mpg at 3/4 throttle.

To the OP, have you checked the rpm at warmed up idle? It will be hard to start and extra cold blooded if the idle speed is too low.

[clKiekhafer]

With Yamaha 150hp 4-stroke at WOT about 3.5mpg (~48mph)and at 60% 5.5mpg (~28-30mph). My "old" 150hp 2-stroke would get ~2.5mpg (48mph).

[Sonicrunch]

Make sure your thermostat is operating correctly. A motor that stays cold will gulp fuel and not idle.

[20lbSloughShark]

2mpg is good on a 75hp?

I guess if it is mounted on a house boat.

Maybe you can expect more from a 2001, my 1984 40 hp Johnson gets about 2-3 mpg. Cedar lake is about 1.5 miles (actually 2 from shore to shore) long from north to south. At full throttle crossing the lake and back is about 1 gallon of gas for me. Back off to 3/4 throttle and I can double the distance on 1 gallon.

[Kyhl]

The 90hp I refered to was an '82 Johnson.

3mph at WOT.

It was a great motor. Simple, carbs and spark. Nothing facny. The power packs were notorious for going bad and I always carried a spare but the motor itself was a tank.