40 HP Merc Fuel Duration

[banchigu]

Hello all what can I expect a 6 gallon gas tank to last on a 40 HP Mercury two stroke engine at 1/2 throttle...

 

[Silvertip]

Re: 40 HP Merc Fuel Duration

Too many variables. We don't knowing the type of boat or year of the engine. A 40 HP engine will burn roughly 4 gallons/hour at wide open throttle.

 

[banchigu]

Re: 40 HP Merc Fuel Duration

Okay good start 17 foot bass tracker, 1985 40 HP Mariner. Also are these good engines, this one has not been used much in 20 years... However, it has been well kept and serviced, so what should I expect from it?

 

[Silvertip]

Re: 40 HP Merc Fuel Duration

I'm certainly not an expert on that particular motor and less familiar with the boat. If the boat is comfortably on-plane at 1/2 throttle I would guess somewhere in the 3.0 gallons/hour range. 4 to 4.5 gallons/hour at wide open throttle, maybe more. Whether or not this is a good engine depends on the care its had. If it has not been used in the last 20 years some serious maintenance needs to be done. Thermostat, water pump, lower unit lub change, and carb rebuilding to name just a few things. Apparently fuel consumption is an issue with you so carb rebuilding is essential for best performance and its insurance for best engine longevity. Clogged jets means lean mixture. Lean mixture leads to engine melt-down. No water (as in bad water pump) means no cooling leading to overheating and engine melt-down. Water/corrosion in lower unit leads to failure of the lower unit (as in $$$$$). Stuck thermostat leads to overheating and engine melt-down. See what I mean?????

 

[banchigu]

Re: 40 HP Merc Fuel Duration

Thanks upinsmoke... it has been kept well and all that you have mentioned has been serviced at one time or another, however, i am going to do some of those things myslef. i just rebuilt the carbs the jets were pretty clogged. i guess now i am going to tear into the thermostat, then the impeller and lower gear case... any further advice would be appriciated on any of the above mentioned projects.

 

[Silvertip]

Re: 40 HP Merc Fuel Duration

There is no need to "tear" into the lower gear case. Simply drain what fluids (lub and possibly water)are in there. Check for metal shavings. If no water or shavings are visible, refill with lower unit lub and you'll be good to go. If gunky looking mixture comes out, its seal replacement time. Now you can "tear" into it. Boat safely.