Rpm on a merc 115hp

[Samonz]

This is my first post on here so I hope you all forgive me if its in the wrong section.<br /> I recently bought a 16ft fletcher with a blueband merc 115, There is a serial number 6201032 if anyone knows the year.<br />It has six cylinders,three carbs and eats fuel like we all drink water.<br />After reading posts on here I now know, its just the way it is.<br /> However after reading posts about rpm and the max being about 5000/5500 I am a tad concerned that my engine rev counter goes of the dial at WOT. It stops at 7000 but the needle goes past it.<br />The speedo indicates 55mph and would probably go past that if the lake was big enough!!<br />Any comments?

 

[andy6374]

Re: Rpm on a merc 115hp

WHOAAAA! your RPM's are way to high. You are/could be damaging your engine. You need a bigger prop. The operating range should be 5000-5500 RPM.<br /><br />-andy

 

[Samonz]

Re: Rpm on a merc 115hp

Hi Andy,<br />How do i find out what prop size is on it?

 

[andy6374]

Re: Rpm on a merc 115hp

I imagine you should be running something like 13-3/4 x 15 x 3 or 13-3/4 x 17 x 3. At any rate you definitely need a bigger prop. <br /><br />-andy

 

[andy6374]

Re: Rpm on a merc 115hp

size is measured by: diameter x pitch x # of blades. <br /><br />Diameter: just what you would think it is. Twice the distance from the center of your prop nut to the tip of one of the blades.<br /><br />Pitch: theoretical measure of how far the propeller should move through the water in one revolution if there was no slippage at all.<br /><br />-andy