# Mercruiser HP increase question...



## Beave (Aug 26, 2002)

Quick question for everyone. Our salmon fishing boat is a Mercruiser with a 1983 120HP Chevy Nova engine. They also offered a 140HP version of the same engine, the only difference being the carbuerator.

We tend to use this as an all-around boat, and while it's perfect for salmon fishing, it lacks a little "Oomph" in the get up and go department when you're trying to pull a skier. That extra 20 ponies would sure be nice on the top end, and at trolling speeds I can't see it affecting fuel economy.

My devious mind wants to see if there's a kit out there to go to 140 or if I can get a 140HP carb for it. 

Has anyone done something like this in the past? My concern is that this may not be a good move for a 20 year old engine. It purrs like a kitten right now, but when you start messing with an old engine like that you can start causing other problems. Any suggestions?


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## Burksee (Jan 15, 2003)

Just my 2 cents.............

My suggestion is would be to leave it alone if you cant get a skier up with 120HP then looking into a different boat would be the best solution.

Your correct in assuming that messing with something thats 20 years old is going to cause you to keep messing with it every time you turn around unless you want to look into doing a complete overhaul of the engine. Also, Unless your changing from a 2-barrel to a 4-barrel I find it hard to believe that the only difference for making the extra 20HP is the carb. There's usually more involved, like the camshaft, intake & exhaust. If you could get 20 more horse by only changing the carb they wouldnt offer the smaller version and a lot more people would be doing it. As for trolling and economy, usually any type of performance modifications have repercussions. I'd think twice before doing anything yourself, it might be worth it to consult a mechanic at your local marina.


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## TONGA (Jul 22, 2002)

Don't wast your time or your money!!!!!!!!!!!!!!!!!!
even if the carb is the only dif..that extra 20Hp will not mean $#!+ at low RPM when you are trying to get a skier up,,it's all about the torque not the HP,,,Horse power is a bi-product of torque+RPM,,,in other words it might be worth 1 or 2 MPH at the top end but thats about it,,,but probably only one!
I bet if you look at the specs for those 2 engines the torque is almost the same,,in fact I would not be shocked if the 120 hit it's peak torque nuber at a lower RPM than the 140,,,I only say that because smaller carbs are more responsive than a larger carbs,,you know it's all about air velocity,,,the bigger carb will start to shine when you get into the hi-RPM range,,,youknow the smaller carb will start to loose it's breath and the big carb will just start to breathe
so the bottom line is if you want more torque the best way to do that is more cubic inches!!!
My rule of tumb on this is, if this is your fishing rig and your pleasure boat and you use it all the time? also it's a sweet running rig...LEAVE IT BE!!!!
IF YOU WANT TO START TWEEKING BUY A TOY!! you know something that will not reck your summer if you break it!!!


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## Beave (Aug 26, 2002)

Yeah, it's a 2 vs. 4 barrel. I'll leave it alone.


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## Burksee (Jan 15, 2003)

Tondga,

AMEN!


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## SalmonSlayer (Jan 18, 2000)

could you change props to get more torque from the motor to the water? Maybe a different pitch prop will provide a better hole-shot while pulling a skier. Just my wild, hair-brained-ideas.


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## TONGA (Jul 22, 2002)

now that is a reasonable idea!


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## Burksee (Jan 15, 2003)

SS,

Excellent idea! Effective and much easier modification, also much more economical too!


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## SalmonSlayer (Jan 18, 2000)

just make sure you get one that's compatible for your boat/motor. I dunno if you can damage a motor with a different prop or not...just check with someone who would know...not me.


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## Beave (Aug 26, 2002)

Good idea. I'm not sure what the prop was sized for. Possibly low end trolling since it was originally purchased soley as a salmon fishing boat.


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