Newbie fuel economy question

[crapaud]

Hi,<br /><br />About to buy a 1990 Yammy 50 2/s on a 19" Orkney (approx 700lbs I think). Current owner is a marine engineer so no probs with engine state and service record.<br />With say, 3 adults, what sort of mileage/fuel economy could I expect from a 25 litre tank(UK measure)<br /><br />Cheers

 

[jim dozier]

Re: Newbie fuel economy question

Without knowing what an Orkney (I am assuming you meant 19 feet not 19 inches ) boat is I would say that it will be underpowered at 50 hp with 3 people in it. I have a 17 runabout with 85hp and wish I had 120 hp. I use about 6 gallons when I go out for a day of about 3 hours running time (guess not measured) blasting around at full throttle. With a 50hp on your boat you better figure on full throttle most of the time.

 

[JB]

Re: Newbie fuel economy question

Moving to General Outboard

 

[Jack Shellac]

Re: Newbie fuel economy question

Welcome to the site. Is an Orkney a displacement type hull? If it's a planing hull, you're going to have problems with just a 50 HP engine. You'll be wallowing around like a French toad. If it is a displacement hull, you should be OK at hull speeds with a 50. Milage would be hard to guess beforehand.

 

[Solittle]

Re: Newbie fuel economy question

I doubt that a 50 would even get a 19'er on plane with 3 adults on board. A 115-150 hp would be about right for that load.

 

[crapaud]

Re: Newbie fuel economy question

Thanks for the input guys.

 

[CharlesW]

Re: Newbie fuel economy question

Can't help with the question, but I did have to add a comment.<br />It is obvious you are a newbie when you use the word "economy" in reference to boating.

 

[digimortal777]

Re: Newbie fuel economy question

an orkney is a displacement hull<br /><br />the 50 horse will be fine

 

[phatmanmike]

Re: Newbie fuel economy question

a 2 stroke outboar will use 10% of rated hp per hour at WOT<br /><br />so a 50hp will use 5 gallons per hour at WOT

 

[crapaud]

Re: Newbie fuel economy question

WOT?? Can someone enlighten me please?<br /><br />Digimortal, do you have an Orkney too?<br />Cheers

 

[CharlesW]

Re: Newbie fuel economy question

Wide Open Throttle

 

[crapaud]

Re: Newbie fuel economy question

aha - also known to us as "giving it some stick!"<br /><br />Thank you Charles

 

[mistermoon]

Re: Newbie fuel economy question

Trying to disabuse the notion that 50 HP is too little power to plane a 19'er. The truth is that just knowing the length of something isn't enough information. Performance (speed) is dependent on a lot of factors, and not least of these is weight. Power to weight ratio matters. For example, I used to have very light weight 18'er with a 15 HP motor. At WOT with a light load, it would run out at 22 mph. Look at Tom Lathrop's Bluejacket 24 design, which cruises at 20+ on 50 horses. http://www.messing-about.com/smallboats/bluejacket.html <br /><br />If you put a 50 on the back of a 4,000 lb deep vee 19' walk around cuddy, yeah, you'd be disappointed. But, if you put the 250 from that 4000 pounder on the back of my lightwieght 18'er, you'd be dead!