Advantages of 3 cylinder over 2 cylinder??

[paulgp6022]

Are there any advantages of a 3 cylinder over a 2 cylinder? I have a 40hp 3 cylinder mercury on my boat. I noticed that they also make a 40hp 2 cylinder. What are the advantages if any? I would guess that the 3 cylinder will last longer than the 2 cylinder because it doesn't have to work as hard.

 

[Fouled Plug]

Re: Advantages of 3 cylinder over 2 cylinder??

The 3 should idle more smoothly, with the work distributed over the additional cylinder.

 

[Steve135]

Re: Advantages of 3 cylinder over 2 cylinder??

Hi the 2 cyl will burn 1/3 less gas than the 3 cyl but the 3 cyl will provived more brake horse power than the 2 cyl. I have both a 2 cyl 70 and 3 cyl 70 I change from the 2 to the 3 and gained about 6 MPH on the same boat same prop!<br />steve

 

[22WRF]

Re: Advantages of 3 cylinder over 2 cylinder??

I don't want to be picky but outboard doesn't have "Brake HP".<br />Outboards Horsepower is rated at the prop or the powerhead on the older ones.<br /><br />Yes a 3 cyl is smoother operating than a 2 cyl.

 

[JB]

Re: Advantages of 3 cylinder over 2 cylinder??

I disagree, Stinky.<br /><br />The triple would be more fuel efficient and smoother idling. Also heavier and more expensive.<br /><br />What 2 cylinder "70" do you have?? What model?? What make and model 70 triple are you comparing it to??

 

[jim dozier]

Re: Advantages of 3 cylinder over 2 cylinder??

I agree with JB, while there are differences between engines with different number of cylinders, displacement (the sum total of cylinder displacement) has the largest impact on power output. A really well designed and built single cylinder engine (up to a certain size)could put out as much hp as an average designed multicylinder of the same displacement. One reason manufacturers go to more cylinders is smoothness, there are certain numbers of cylinders and layouts (V angles) that provide smoother firing orders. Another reason is flow problems with really large piston bores. I suspect that in some cases it would be economical to offer a detuned version of a larger horsepower model as a lower hp version.

 

[Steve135]

Re: Advantages of 3 cylinder over 2 cylinder??

Hey JB the two motors were a 1985 Tohatsu 70hp 2 cylinder and a 1984 Evinrude 70hp 3 cylinder. Both had till trim control and I used the same size and pitched prop. It was like night and day the Evinrude was by far a better motor. As far as the brake hp comment LCM-8 you are correct I was mis-spoken and mixed aircraft and boating together. OOPS! steve