Classic AquaSport

General Aquasport Forums => Aquasport Discussion => Topic started by: Anonymous on August 31, 2005, 11:46:30 AM

Title: Gas and draft
Post by: Anonymous on August 31, 2005, 11:46:30 AM: Two questions about my AS. I have a 1974 17' CC. what does she draw?

Secondly, i have a 50 hp merc on there. not a speed demon by any means, but fast enough to get me where i need to be. my question is this, how can i estimate the fuel consumption? i'd like to take this boat over from hyannis to nantucket, and want to see how much gas i need.

Thanks!
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Post by: Radioshop on August 31, 2005, 02:24:06 PM: This is a tough one without the benefit of a floscan or such device. I would try topping the boat off, running at a comfortable cruise for an hour or, two hours, but not fractional increments. Vary the wind/current conditions. Refil the boat and then divide gallons by hours operated, and you should get a picture. This should at least get you into the ballpark to where you can make a comfortable estimate. You could also get a 5 gallon portable gas tank, see how long it takes to kill that, multiply by 8 and, you'd have an idea too.
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Post by: Keith Knecht on September 01, 2005, 11:27:24 AM: Hey Newtown,

Just kind of a rule of thumb thing is a the horsepower divided by ten equals the GPH at not quite full throttle or 5 GPH. Crusing speed would be around 2 1/2 to 3 MPG. That's a real rough gestimate. It is affected by a lot of things and that boat with a 50 is a little underpowered. It might go slightly higher near WOT or if it's loaded down. Hope that helps but don't call me if you run out of gass. It's a long way from Tampa.

Keith
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Post by: Keith Knecht on September 01, 2005, 11:37:05 AM: Dang,

Forgot to answer the second part. The hull should draw about 7 1/2" with the motor out of the water. I'd expect that you could tilt up the motor and run in 10-12". My 25 would run in about 14" with the motors tilted up. Correct me if I'm wrong. There's a few 170 owners on this site that should be able to give you a lot more accurate answers than me. The smallest AS I've owned is a 19' 6".

Keith
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Post by: RickK on September 02, 2005, 05:48:50 AM: I have a 110 'rude and get around 5-6 gph at cruising speed (for me, around 4000rpm = 30mph. Max 5200rpm=38mph). Each motor will vary and of course the elements can dictate your fuel consumption too.
As far as draft goes; drifting with motor up I can get into very skinny water - the 7 1/2" that Keith mentions sounds about right - never measured but was amazed as I drifted. Under power, the lower unit max tilt that still allows water into it is the answer (unless you have the special pickup on the nose).
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Post by: Keith Knecht on September 02, 2005, 10:04:28 AM: That rule of thumb works about right for Rickk. Take his 110 Hp drop the 0 and you've got 11 GPH at WOT and about half that at crusing speed or the 5-6 GPH that he mentions. With the 50 it's 5 GPH at WOT and 2 1/2 to 3 GPH at crusing. That should come pretty close on your boat unless the 50 HP is too much under power for the hull.

Keith
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Post by: John Jones on September 03, 2005, 08:15:27 PM: That rule of thumb works for me too. I have a 22-2 w/ 225 Oceanrunner. I can hit 22/23 gph on the Navman fuel meter at WOT.