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I have a 1976 13' sport, converted to super sport interior. I put a new mercury 40 hp 4 stroke on her, the dealer put on a prop with id as follows hu 10-1/2" x13" also stamped c1-h1-1013 with name turning point. I have not put a tach on her yet as I do not want to cut into the wood, she's beautiful, but I know I need one to see what the engine is putting out. I did put on an se300 hydrofoil to help keep the bow down at low speeds. I have had her on the water three times so far and gas mileage is awful. Any ideas on it. Thanks!

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Just as a guess - is the motor mounted all the way down? If so, your foil is probably acting like a sea anchor. Try removing the foil and raising the motor. Raising the motor will help keep the bow down and you may find you don't need the foil at all.

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Thanks for the tip. I'm going tomorrow to the boat guru in our area, he will put a tach on her and go from there.

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Regardless of the prop and tach, make sure the engine is mounted at least 2 holes up.

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We put a temp tach on her yesterday, she was able to get to 6000 rpm barely. We put on a smaller prop and test ran her. She shot out of the hole like lightning and was to 6000 rpm easily. No we will take her out to see about the gas mileage problem. Also the motor is mounted on the second hole from the bottom.

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Outboard propellers are not uniform and selecting the correct one is complex.

Your part # showed up as a Hustler prop. http://www.amazon.com/Turning-Point-P...B0013JZ9M6

Simply put, its a cheap aluminum prop.

Boston Whaler sells their 130 Sport with a 40 Hp Mercury engine and a 10.1” x 14” Spitfire prop. I would try that prop first.

When moving sizes, you CAN'T change brands. Size is not universal across brands. If a Spitfire 14" pitch is too much (RPM's too low), try a Spitfire 12"

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We moved down in prop to a twelve pitch. Runs faster but fuel consumption is still bad. 1 hour on the water = 1/4 tank of gas. I have a 14 gallon tank with 13 gallons in it. Something has to be wrong somewhere. HELP!

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That doesn't tell us the whole story.
Some motors have 5 mounting holes and some have 4 mounting holes.

How many mounting holes does your motor have?
4 or 5 ?

And the standard is telling us how many holes up is the motor mounted.
What hole is the bolt in from the top? The bottom doesn't do anyone any good as you can see.
http://www.whalercentral.com/articles...cle_id=106

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From the top down I'm in the third hole. Mine has 4 holes.

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Excellent.

Now we all know you are 2 holes up and that should be right.

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From a quick look at Mercury's performance reports for your motor, I see fuel burn rates as high as 3.8 gallons per hour. Of course that's going fast - cruise speeds were around 2 GPH. Still not that different than what you're seeing.

It's not clear to me you have a problem other than that cheap aluminum prop. You're doing a nice job resurrecting a classic, and I'm sure it cost a few bucks - do yourself a favor and spend just a whisker more and get a good stainless prop. No sense handicapping that new motor with yesterday's technology.

Tim

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Translated that is

.25 x 13 gallons = 3.25 gallons.

If we want to truly verify there is an issue, we need specifics.

What speed and rpm's were you going in the hour? What was the load/passengers in the boat.

It is feasible you are dialed in correctly. It could also be true your prop is inappropriate for the hull and motor and totally inefficient.

The only way to know is to test the boat, change a variable and retest. It needs to be methodical to provide accurate results.

I would forget about gas mileage till you verify you have the correct prop on the engine. You want the engine to run ~5500 rpm's at WOT with you, gear and full load of fuel.

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Wot I'm running at 6000 rpm. I removed the hydrofoil and it stopped bouncing at wot. But gas mileage went down. With the hydrofoil gas mileage was much better. I will be going to get a ss prop on my first day off.