More Power from '07 Merc. 9.9 4-Stroke

7

70Stang

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Jul 4, 2007
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I recently purchased a 2007 Alumacraft Crappie Deluxe boat and a 2007 Mercury 9.9 HP 4-stroke. The boat is 16'. I was told by the dealer that the 9.9's today had more power than the old 9.9's. After running it for a week (4 gallons of gas) fishing trip, I definitely need more power. I realize that I should have gone with at least a 15 HP motor.

Question: I know the only difference between the old 9.9's and the old 15's was the carb. Is this still true? Can I just swap carbs and have a 15 HP motor? If not, what can I do?
 
N

noelm

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Mar 8, 2005
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Re: More Power from '07 Merc. 9.9 4-Stroke

you probably could just swap the carbs and end up with a poor performing, gas guzzling motor, better off to do a trade or sell and repurchase.
 
R

Rancherlee

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Re: More Power from '07 Merc. 9.9 4-Stroke

your boat is rated for a 30hp, a 15hp isn't going to do much better than a 9.9 does. The boat alone weighs ~500#, I'd be looking to trade up to the new mercury 25hp EFI 4 stroke.
 
7

70Stang

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Re: More Power from '07 Merc. 9.9 4-Stroke

noelm said:
you probably could just swap the carbs and end up with a poor performing, gas guzzling motor, better off to do a trade or sell and repurchase.
Click to expand...

I did some research this morning and found out that the 9.9 & 15 HP outboards share the same block and even weigh the same. The only difference is the carburetion and exhaust.

For those interested, here are the part numbers for the conversion. And, if performed by a factory authorized dealer, they do not affect warranty.

15 HP Carburator - Part #1392-9726T18
15 HP Exhaust Kit - Part #41344-T6
You will also need the carburator and exhaust gasket kits.
 
tashasdaddy

tashasdaddy

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Re: More Power from '07 Merc. 9.9 4-Stroke

but is the gained hp worth the cost, compared to the difference in performance, on a boat rated for 30 hp.
 
Silvertip

Silvertip

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Sep 22, 2003
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Re: More Power from '07 Merc. 9.9 4-Stroke

This is a futile effort at making a small engine try and move mountains. A boat rated for 30 HP should not have an engine smaller than 75% of that rating to provide just adequate performance. That's 22.5 HP or the closest engine bigger than that would be a 25. And since its a four stroke, I'd max it at a 30 HP four stroke.
 
CATransplant

CATransplant

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Re: More Power from '07 Merc. 9.9 4-Stroke

tashasdaddy said:
but is the gained hp worth the cost, compared to the difference in performance, on a boat rated for 30 hp.
Click to expand...

Not only that, but the cost of buying those parts and having them installed is going to be way more than the difference in price between a 9.9 and a 15, since parts are always way overpriced.

As has been suggested, I think this guy should cut his losses and see what the dealer will give him in trade for this 9.9 on a 25.
 
TOHATSU GURU

TOHATSU GURU

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Re: More Power from '07 Merc. 9.9 4-Stroke

The 2007 Mercury 4-stroke 9.9 is maxed out at 9.9 and cannot be converted to a 15 as it is a completely different frame size.
 
JB

JB

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Re: More Power from '07 Merc. 9.9 4-Stroke

Take it back to the dealer that conned you in the first place and get full credit on a Honda 25. If they cannot supply a Honda settle for the Merc EFI 4stroke 25.

The sales dude who sold you the 9.9, which has no more power than any other 9.9 made after the mid-80s, knowingly lied to you about the engine and knowingly sold you a grossly underpowered boat.
 
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