# What's the diff between 1cyl and 2 cyl motor of the same HP?



## Quickstep192 (Jan 6, 2001)

I'm shopping for a new kicker for the sailboat. I want to reduce weight both to raise the aft end of the boat and to make it easier to remove, so I'm considering a 6hp to replace the current 8hp motor. While shopping, I noticed that Yamaha makes two different 6hp motors; one that's two cylinders and one that's just one cylinder. If both are 6hp, will the two cylinder model be able to produce more thrust than the single cylinder? Ordinarily, I'd incline toward the 2 cyl, but it's considerably heavier. Any thoughts on this?


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## dabnis (Jul 29, 2007)

I have had both but not of the same HP. My guess is that the 2 cyl may be a little smoother? Don't know about the thrust. If they both have the same prop, gearing, and RPM rating they could have the same thrust? Probably Tohatsu Guru knows the difference?

Dabnis


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## eherlihy (Jan 2, 2007)

2 Cyl - smoother running, heavier, more stuff to break, easier to start.

1 Cyl - Lighter, more difficult to pull the cord when starting.

WHICH Yamaha are you looking at? The website (Yamaha Portable Specifications) says that the F2.5 to F6 are all single cylinder, and the F8 to F20 are twins. There is no overlap in HP between the single and twin cylinder models.


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## Tim R. (Mar 23, 2003)

Get an older model('87-2000?) Johnson or Evinrude 4 hp twin. It is 2 cyl and only weighs 33lbs. Integral tank and ext hookup. N and F gears. Twist throttle handle.

I have owned 2 of these and they are great little motors.


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## eherlihy (Jan 2, 2007)

treilley said:


> Get an older model('87-2000?) Johnson or Evinrude 4 hp twin. It is 2 cyl and only weighs 33lbs. Integral tank and ext hookup. N and F gears. Twist throttle handle.
> 
> I have owned 2 of these and they are great little motors.


Tim,

Is that 2 CYLINDER or 2 CYCLE?

I have a 1 cylinder 2 cycle (two-stroke) 3.3 HP that weighs 29lbs. I can't imagine anything lighter...


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## T37Chef (Oct 9, 2006)

Never ever again will I buy a one cylinder outboard! Nough said


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## tommays (Sep 9, 2008)

The single cylinder motors are foul vibration beasts


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## Omatako (Sep 14, 2003)

More cylinders generally means more torque but I wonder whether it is noticeable in such a small motor.

Otherwise everything has already been said.


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## Tim R. (Mar 23, 2003)

eherlihy said:


> Tim,
> 
> Is that 2 CYLINDER or 2 CYCLE?
> 
> I have a 1 cylinder 2 cycle (two-stroke) 3.3 HP that weighs 29lbs. I can't imagine anything lighter...


Ed, that is 2 Cylinder, 2 cycle. easy to start, runs smooth and fairly quiet(compared to a 1cyl)


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## kcbillb2 (Nov 26, 2010)

Yeah, I've got one of those. 1994 Johnson 3 horsepower, 2cyl, 2 cycle. Nice and light, runs great. Actually runs great now that I've rebuilt the carb and cleaned all the ignition connections...

Came with the boat, I pulled the cover off and discovered the previous owner sure never did any service on it. The OLD dead wasp/hornet nest in there was kind of a tip off...



treilley said:


> Get an older model('87-2000?) Johnson or Evinrude 4 hp twin. It is 2 cyl and only weighs 33lbs. Integral tank and ext hookup. N and F gears. Twist throttle handle.
> 
> I have owned 2 of these and they are great little motors.


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## svHyLyte (Nov 13, 2008)

Quickstep192 said:


> I'm shopping for a new kicker for the sailboat. I want to reduce weight both to raise the aft end of the boat and to make it easier to remove, so I'm considering a 6hp to replace the current 8hp motor. While shopping, I noticed that Yamaha makes two different 6hp motors; one that's two cylinders and one that's just one cylinder. If both are 6hp, will the two cylinder model be able to produce more thrust than the single cylinder? Ordinarily, I'd incline toward the 2 cyl, but it's considerably heavier. Any thoughts on this?


The power produced by an engine is proportional to the Mass Flow through the engine--i.e. the Mass of Air/Fuel. For a single cylinder to produce the same power as the two cylinder, it must turn at twice the rpm's if the bore and stroke are the same in both engine or some multiple of the rpm of the two cylinder's rpm if the bore is greater-which is not uncommon. As previously noted, the single cylinder will seem to have more vibration although that is sometimes off-set/mitigated by a much larger/heavier fly-wheel. Old, slow-turning, gas engines seemed to produce enormous torque but weren't known as "Rock Crushers" for no reason.


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## ilikerust (Apr 19, 2010)

No response to the point that the Yamaha website shows only one model of 6 hp motor, and it's a single cylinder? And they are all 4-strokes.


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## OtterGreen (May 10, 2011)

i had a motorcycle that was a single cylinder when i was going to school in FL. one thanksgiving i drove from Palm Beach to see some extended family in Marco Island. man oh man.. beside the terminal sunburn from the sleeveless shirt, and welts left from the bugs on alligator ally, there was no fuel gague and fuel points there are few and far between. so, every 30 minutes i would pull over, knock the tank and have a peek and sit for 10 mins just to get the feeling back in my hands. fun trip but 6 -7 hours later i had had enough.


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## tdlpps (Feb 25, 2011)

OtterGreen said:


> i had a motorcycle that was a single cylinder when i was going to school in FL. one thanksgiving i drove from Palm Beach to see some extended family in Marco Island. man oh man.. beside the terminal sunburn from the sleeveless shirt, and welts left from the bugs on alligator ally, there was no fuel gague and fuel points there are few and far between. so, every 30 minutes i would pull over, knock the tank and have a peek and sit for 10 mins just to get the feeling back in my hands. fun trip but 6 -7 hours later i had had enough.


This is similar to what one feels when undertaking a long trip primarily under power with a single cylinder outboard. I've done one multi-day trip and a single all day trip with a single cylinder Tohatsu 6 hp pushing my 26 foot boat along.

It's fine to get me out of the marina, but the vibration and noise gets old really quick. Fortunately, the Tohatsu has been reliable, sips fuel and has not had a mechanical issue. My next motor will be a two cylinder, however, even if it means moving weight around to compensate for the extra 40 pounds on the stern.


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