Mark 3 gas mileage

[skoskii]

Hi,

I have a Zodiac Mark 3 with a Yamaha 50 2 stroke. I am planning on doing a larger lake crossing but do not a have good idea of the boats gas mileage.

I have only had the boat one year and have not done any kind of distance versus fuel used tracking.

Does anybody have a ball park estimate so I can calculate how much fuel I need to bring? Need to go approximately 150km with out refueling. I think this is too far...

Thanks,
igor

[Polwart]

Igor,

There is a general rule of thumb for outboards at full throttle which is 1 US Gal / hr for every 10 HP of engine. So if you have a 50 HP engine it will burn about 5 US gal every hour.

If you are looking to do 150 km, about 80 Nm. If your top speed is 40 knots (which might be optimistic but it keep the numbers simple!), you'll be out for 2 hours at full chat so need 10 US gallons (about 31L). (if you only do 20 knots at max throttle then double this)

There is another general ribnet rule of thumb (very rough) that Ribs cruise at around 1 L/nm (+/- 25%) so that would suggest 80L (21 Gal). The SIB people with small engines smirk at these numbers though and can get double the range!

So very roughly you'll need 10 Gal minimum to make that journey. If its choppy you'll need more. If there's a navigation error you'll need more etc... so on "out and back" trips people often work on 1/3rd out, 1/3rd back and 1/3rd spare (which is a 50% reserve). If you can definitely fuel at the far end then 15 Gal would be the minimum for me to consider that and I'd be checking it 1/4 and 1/3rd of the way across and recaclulating actual usage and range before deciding if I needed to turn back.

[skoskii]

That's great information!

Thanks Polwart!

[prairie tuber]

Whatr Polwart said sounds about right. You would probably be get somewhere around 4.5-5 mpg (28-32 km/L) at wide open throttle with a 50 hp 2 stroke and a Mark III sized boat while on flat water. Are you looking to cross Lake Ontario? Assuming that it is about about 60 Km across, I would take 60 liters (each way). You could probably do it with around 40 liters if the water stays relatively calm, but if the lake blows up it is essential to have plenty of fuel in reserve.

[C-NUMB]

SIB's performance is maybe litle more sensitive to weight than hard boats, so how much fuel You need pends also on your load. Last summe did some longe distance boating with the bombard (420) and 25 hp. At moderate cruising speed and good conditions averaged 0,35 L/NM(2 not so heavy persons, some gear and fuel).

Adding one person, increased consumtion to 0,5 L/NM. Rough weather/ swell would increase consumtion further. These figures as i remember now but should be accaurate enough.

You have a bigger boat so I would fuel 20 Gal, then You should be on the safe side, and dont need to worry all the time.

[Delta 15]

When I make longer range trips (15' Avon with 40HP 2 stroke) I bring one or two 5 gallon cans as a reserve but I don't mix the oil until I put it into the main tank. That way if I don't use the reserve gas I can put it in my truck and I don't have excess 2-stroke gas sitting around until the next trip.