Question about 4 stroke small propellers and gear cases

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I've been looking at 60hp Mercury 4 strokes for an upgrade and i've noticed the lower units are skinny and the props are very small or at least they appear to be. Now i've been running a 1999 2 stroke 60hp Mercury for 8 years and it's lower unit is big and beefy with a large prop. I swear i don't think the prop on the 2012 Merc. 4 stroke was bigger than 10" across if it was that...Why so small?

 

[Texasmark]

Re: Question about 4 stroke small propellers and gear cases

Swinging big props at low rpms (2.3:1) mean lots of thrust to push large/heavy loads. Small dia props running low gear ratio's ('94 60 triple looper 2 stroke is listed as 1.64:1) are for light fast boats and are lighter. Realizing there are other differences affecting weight, like 84 cu in over 52, the 60 ELPT weighs in at 207# and the next engine in the series (75 hp) with the bigger foot weighs in at 305#. I guess Merc figures that these engines will be mated to that kind of boat.

Case in point is their mid range "Big Foot" whereby they put the large lower unit (2.3:1) on a smaller engine (40-60 hp) than what it was originally designed for (75 up triple and quads) ...used for pushing toons. Scott-Attwater/McCullough did the same thing back in the 70's with a 14 hp turning a 13" dia prop for toon applications.

That's the way I see it and am open for other comments from knowledgeable folks on here because I have often wondered/suspected the why for a long time...

Mark

 

[Faztbullet]

Re: Question about 4 stroke small propellers and gear cases

Now i've been running a 1999 2 stroke 60hp Mercury for 8 years and it's lower unit is big and beefy with a large prop.

Sounds like a "bigfoot" gearcase.The 40, 50 and 60hp are available with either standard or BigFoot gearcases. BigFoot models are for pontoons and large boats(over 16ft), while the standard gearcases are ideal for aluminum fishing boats, bay boats, and inflatable boats.