TOPIC: How Far Do You Get per Tank of Gas?

OK, so there's lots of factors there, but what's your estimated mileage and for what engine?

with 2 228 HP cruzerz I fill up @ about $900 that's 200 Gallons and cruse for 2 days around the lake. If I run WOT i can watch my guage fall but in the numbers it's no wore than my 135 Evinrude or my 80 Merc in GPH...... Most all Boats burn about 1 mpg. 2 at best less than 1 at worse.

merc 700..i'd say 1 mpg...ron

Judging from the oil slick in my 'test tank' after firing up the fat 50, probably jut far enough to get me to the next gas pump . I don't see myself doing a lot of long distance cruising this summer, gas is going to be very expensive! Luckily, I've got some nice, peaceful coves that I can slip in to just a few minutes from the launch ramp.

These old beauties are certainly not known for Efficiency... Some of the newer motors are pretty amazing, though.

I think Heather's answer is right on. No more than 2 mpg, although that's about what I get with my old weak '63 Merc1000 pushing a 300# boat with two people and 12 gallons of gas. I'm gonna buy another 6 gallon tank this year for more distance. Given what's going on with gas prices, I may be using my electric trolling motor quite a bit...

Frank

With my 17 food. Wagemaker Empire Clipper and a 1970 merc 500 I can go about 24 miles to a 6 gallon tank at 95% throttle... so about 4 miles to a gallon? .. Actually using the Google Measurement tool looks to be more like 30 Miles.. so 5 miles to the Gallon... if the measurement is correct.

Marine fuel consumption is better rated in gallons per hour. A 5hp engine on a 200lb boat is going to burn less than a 50hp engine on a 1,200lb boat. It's almost impossible to weigh one person's numbers against another, unless the boat, motor, and boat conditions are nearly the same. With any engine, the faster it turns, the more gas it will consume. If you prop a boat for towing skiers & tubes, it'll have a great holeshot, but the cruise range will suck. On the other hand, if you prop for low RPM at cruise, the fuel consumption can be reduced significantly. Most "glassic" boat will cruise the most efficiently at speeds between 16 and 25 MPH. go slower or faster than that, & it will burn more fuel per mile traveled.

I don't know, but you better have a second tank to get home on.

On the sail boat 36' going 8 knots I have a gone 280 knots on 18 gal diesel no sails. On the Robalo with twin 250 Evinrudes in fuel saving speed (1/4 off full speed) about one mile per gal loaded with people and scuba gear

On the 1948 Lone Star (12') with the 1948 Champion (4.7hp) I can run the lake all weekend on less then 2 gals...that puts it some where near 4 to 5 miles per gal or better (Never really checked).....This motor has to be off less you want to be going....no gears .... forward or off

Hopefully back to the dock......

Last summer we checked this topic out at the lake with my 68 Creastliner with a 55hp Evinrude also of 68 vintage.We used a GPS to track time and distance only. With a full 6 gal. tank, 2 people on board and 1 fat small dog we started the GPS from the time we first fired up the old motor.Ran for 2hrs.46min. Before running out of fuel. Distance was 36.2 mi. This was at different throttle settings, overhalf at full throttle. So that gave us 6 mpg. On the second day we got only 32 miles to 6 gals. time about the same. The only differance was on day 2 when to lake had more chop on it. After much discussion with other boaters it comes down to weather conditions, water conditions and various other factors. I never trust a set fuel/ distance setting. Spare fuel and paddles. Skip.

Hmm, the campsite I want to get to is 12 miles from the closest boat launch. Sounds like 24 miles on 12 gallons with an Evinrude Starflite 100 might be touch and go. Might be time to look at adding a second tank.

Good topic.
The old rule of thumb for carbureted two strokes was 1gallon per 10hp per hour at wide open throttle.
So for a 115hp outboard, 11.5gph at wot.
A 50hp would be 5gph.
A 25hp would be 2.5gph.
Rough yardstick of course, so your results may vary.
It seems to work well for prop shaft hp.
It works pretty good for wot whether 2 or 4 stroke, or direct injected. But at lower engine speeds the 4 stroke and direct injected engines will of course better the carbureted two stroke.
Google some outboard engine tests and you'll see fuel consumption at wot throttle is pretty close to that old formula.

I always recommend folks take a six gallon tank, write down the start time then use the boat as they normally run it. Write down when you run outa fuel. Now you have a great data point for how much fuel you need to carry. Running outa fuel is not good....

Running a 140hp (115 prop shaft) Merc inline six on my SKagit 20 I averaged about 6gallons every 52 minutes over the years.
Not bad.
I could dump the tank in 37 minutes if I kept her pinned, I may have even done it in less time but would have to look.

You've just got to test every engine with every boat. there is math that will tell you what it should be but 3 factors come into play. Boat weight, Engine size and prop pitch....

The best way is to take a 1 mile known distance during calm wind, weigh 1 gallon of gas in a tank, run the one mile and weigh the tank after the run. It's easy and there is no question after. no tools needed and will be specific to your set up at that time. Google earth is a great way to find points on a lake to find that 5280 feet.

My 73 Johnson 115 V4 (19P prop) on a 17' Glastron AquaLift II (tri-)hull will run an average of 3 1/2 hours on a 12 gal tank. Hard running 2 1/2 or rough water is closer to 3, easy cruising on calm water closer to 4. (I carry a spare 6 gal tank, just for peace of mind). A 24 mile round trip shouldn't total more than 2 1/2 hours, assuming you run at around 20 mph. You should have enough to make it with some to spare, but I like having a reserve "insurance" tank to make sure anyway.

Interesting question on "mileage" though, I'll try to remember to set the GPS next time and see what the distance traveled reading is.

Bill - reading what you posted while I was typing, I don't feel so bad about my "consumption" now. FWIW, gas just hit $3.70 a gallon for premium here today.

I run a 17' Thompson Sea Lancer with a '63 Merc 850. At about 2/3 throttle and about 28 MPH by the on board speedometer I get about
3 MPG. On the Mississippi the permanent channel markers have mileage markers on them ( the miles from Cairo, Illinois where the Ohio River comes in) and I usually make a round trip with equal amounts upstream and down. The boat and motor weigh about 1100 lbs plus equipment, gas, passengers, ect. She will run out at about 35-36 MPH but it makes a HUGE difference in mileage. I think we will be doing alot more slow cruising this year also.
I have 2 12 gallon tanks on board and have a 6 gallon I can throw in if we are taking a long trip. I like to always be on the safe side. I think it would be a long ride home using the Minnkota.
Bill

Nice thing about rivers is that you can always drift down them when you run out of fuel, don't work to well on lakes. Skip.

MarkS wrote:

My 73 Johnson 115 V4 (19P prop) on a 17' Glastron AquaLift II (tri-)hull will run an average of 3 1/2 hours on a 12 gal tank. Hard running 2 1/2 or rough water is closer to 3, easy cruising on calm water closer to 4. (I carry a spare 6 gal tank, just for peace of mind). A 24 mile round trip shouldn't total more than 2 1/2 hours, assuming you run at around 20 mph. You should have enough to make it with some to spare, but I like having a reserve "insurance" tank to make sure anyway.

Interesting question on "mileage" though, I'll try to remember to set the GPS next time and see what the distance traveled reading is.

Bill - reading what you posted while I was typing, I don't feel so bad about my "consumption" now. FWIW, gas just hit $3.70 a gallon for premium here today.

Mark, I run out one old metal omc tank first and a newer plastic see through tank last and set it out in the floor and keep an eye on it.I've ended up having a quart left when I get to the dock.. Years back ,I had extra people show up at the lake I didn't figure on and run out of gas. Found out the hard way,load makes a difference. lol Old timers used to say 75 johnson/evinrudes would burn 6 gal in 45 min at WOT, but you could back it off a little to retard the spark and get better mileage.

I just need to decide if I want to get a 6 gallon reserve, allowing me to keep the current location of the battery, or go straight for the 12 gallon and buy longer cables so I can move the battery forward. In the end the 12 gallon would cost me about three times as much.

You can never have too many tanks.

My Pontoon was powered by a 89 30hp Johnson. It did pretty good when I just cruised around at slow speed. When I put the 62 Homelite on the pontoon it does about the same. But no Blue smoke! Also idles smoother. One added advantage, savings of 16 ozs. of 2 cycle oil for every 6 gal fuel I use. Also another plus. The Homelite has 25 more hp.
Right now I'm running a 3 blade 9" pitch prop. I do have a 4 blade 8" pitch prop I got from Bill R. I use if I plan on cruising with a full load of cargo and people.
I also have a Larson All-American powered by a 59 Fat fifty and a 62Lone Star Fleetwood powered by a Merc 700FGS They are pretty close in fuel comsumption. Of course different motors and different loads.

I have a hard time using up one 6 gallon homelite gastank full I always bring a second but never empty it and I dont always go slow thats running a 14 pitch prop on the thunderhawk the skagit is running an 11 and still as good although not as fast as the thunderhawk.

billr wrote:

Good topic.
The old rule of thumb for carburerated two strokes was 1 gallon per 10hp per hour at wide open throttle.
So for a 115hp outboard, 11.5gph at wot.
A 50hp would be 5gph.
A 25hp would be 2.5gph.

Now here a real good way to look at unlike a car, your not looking at Miles per Gallon, rather just hour much your motor burns in Gallons-per-hour.

now I really like to make this even more complicated by suggesting in a cheap in line fuel flow meter, you will be surprised at what your peek area is for the most fuel effencent burn.