Increased power from a 140 hp Mercruiser

theoldwizard1

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Feb 25, 2014
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Is there any cost effective way to increase the power of one of these engines by 20-30 hp ?

New cylinder head, etc ?
 

Rick Stephens

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Install a v6. About it. The motor is an industrial motor. It won't last if you bump it. Not that it hasn't been done - saw a turbo on one once. Impractical though as you end up lugging the motor until the turbo ramps up. Cheaper and much more effective to darn near double the horses with a V6.
 

thumpar

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Jun 21, 2007
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You can't really do anything to a 140 to make make more power. Anything you do would be expensive and not get you much. Rick is on the right track but keep in mind you would probably need a drive with a different ratio.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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The 3.0 is like the yugo's of the motor world. Its a basic industrial motor, that works ok, and is in entry level models.

Not much available for cheap to do anything with. Custom cam, custom pistons and a bunch of custom head work to get another 30hp. For the cost you could upgrade to a 4.3 or 5.0 for less $
 

Silvertip

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Getting more power from a gas engine involves modification of the three "C's" (cam, compression and carburetion). When you mofify any of those factors you manipulate the torque and power curves up or down the rpm band. More power means going up the rpm band. Messing with camshafts on a marine engine means you run the risk of pulling water back through the exhaust into the engine. Messing with carburetion is generally ineffective unless you also mess with the cam. So the long and short of this is you got what you got. If more power for marine use was practical, GM and Mercruiser would have done it long ago.
 

Starcraft5834

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The 3.0 is like the yugo's of the motor world. Its a basic industrial motor, that works ok, and is in entry level models.

Not much available for cheap to do anything with. Custom cam, custom pistons and a bunch of custom head work to get another 30hp. For the cost you could upgrade to a 4.3 or 5.0 for less $



I like my "YUGO" :fish2:. I try to take it easy on the old girl :)
 

Bondo

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Is there any cost effective way to increase the power of one of these engines by 20-30 hp ?

Ayuh,...... Sell the boat, 'n buy one with a bigger motor,.......
 

fishrdan

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Jan 25, 2008
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Is there any cost effective way to increase the power of one of these engines by 20-30 hp ?

New cylinder head, etc ?

Cost effective? Nope...

Modern 3.0L engines are 20-30ish HP more powerful than old 140HP engines since the newer engines are rated at the prop and older engines rated at the crank. Adjust for drivetrain loss of 15-20% and that 140HP is more like 110-120HP - at the prop. The newer engines have a different compression ratio, better designed head and manifold, bigger carb, better ignition,,, and I speculate the cam is better too.

That said, it wouldn't be worth the time, money and aggravation "upgrading" to a modern 3.0L engine.
 

theoldwizard1

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Feb 25, 2014
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I guess i was wondering, with modern technology, if anyone has tried to make an aluminum overhead cam. Of course the more I think about it, that would require new intake and exhaust manifolds, fuel system, exhaust system, etc, etc. any "decent" modern engine should make about 60 hp/liter, or about 180 hp from 3.0L.

Then there is the Yamaha F200 outboard. 4 cylinder, 2.8L, DOHC and 200 HP or 71.4 hp/liter !!
 

thumpar

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Jun 21, 2007
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If you want high performance stuff you need to get into a small block or big block. The I4 is put in budget boats so there really isn't a market for the expensive stuff for them.
 

achris

More fish than mountain goat
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May 19, 2004
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... etc, etc. any "decent" modern engine should make about 60 hp/liter, or about 180 hp from 3.0L.

Not from a MARINE engine. There is no gearbox, so the engine needs to produce bags of usable torque from low down, that means sacrificing power at the top end. I could build a 350 V8 to make over 700hp at 6,500rpm, but anything less than 4,500 would be off the torque curve and unusable. And since most boats work in the 2,500 to 4,800 rpm range, not a lot of good.

Now, your 3 litre. Merc did manage to get about 160hp when they put injection on it, but the bottom end didn't last long. Hence they pulled it back to 135hp....

As already stated, want more power, get a bigger engine.

Chris......
 
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