Prop discussion

[ttriebler]

I have a 1976 115hp straight six Mercury outboard. The prop is a bronze 3 blade unit - only identification on it is a "21" stamped into it. I assume then that this prop has been modified to be a 21 pitch prop. It's got some serious cupping on it too. (ps the boat is a 14ft Pride Cheetah and is hitting 40mph).<br /><br />Are these props interchangeable with other mercury props? Are there any advantages to going to aluminium or stainless steel? I was thinking of trying a 21pitch stainless prop as I prefer top speed to towing skiers.

 

[mellowyellow]

Re: Prop discussion

aluminum and stainless steel or much more common<br />props on these motors. 115hp on 14' boat seems<br />a bit high and 40mph seems a bit low???<br />I personally have a 19 on my 115 merc and am pleased. <br />try to find a shop that will let you<br />try a few different props to see which performs<br />best for you.<br />good luck,<br />M.Y.

 

[bluebyyou]

Re: Prop discussion

Sounds like you're WAY over propped to me. What's the max RPM the motor will run WOT? Should be in the 5000-5500 range. I'd try a 19 or even a 17 pitch prop.

 

[rodbolt]

Re: Prop discussion

hello<br /> first ya gotta tell us your present RPM at wide open. the stock 115 yammi on my monark mcfast15 runs a modified 21 pitch and will bump 6200 if pushed at just over 60 mph. alas that is also about the speed my steering cable locks.so a 21 on a 14 is in the ball park. anyway post back on the RPM.