If you have read my other treads, you know I had downsized to a ?99 60HP 2-stroke Bigfoot from a I-6 115 and have been trying to get the correct prop for it. The Marina originally put a 14/13 on it, which produced a WOT RPM at 5800. (and you could tell ? the motor was louder)
I then put my old SS prop, which I was told was a 15P. That gave me 4800 RPM, but the speed appeared faster, and the motor was quieter. (No I do not have a GPS unit and the speedo on the boat reads between 15 and 18MPH). I figured that the SS prop was not a 15p, as it dropped the RPM by 1000 (and that?s with just one person)
Well I went and got a 13.75 /15P Al. prop from the marina, and put it on, The prop was a new one from Mercury). But when I went out, it only indicated 4800 RPM WOT and acted the same as my SS prop.
So I went from a 13P to a 15P, which you guys say should have dropped the RPM by 2*200 or around 400rpm, which would have placed the WOT RPM in the range of the motor. (Which I was told is 5000-5500).
I was told you should not allow the motor to lug, so I went back to the 14/13P and WOT RPM again indicated 5800, so I just won?t run WOT. (It does appear to run slower, but that may be a perception, as I have no way of accurately measuring speed ? I put a hand held GPS on my Christmas wish list.)
I guess this 200RPM per 1? pitch change does not apply for pontoons, as nothing else changing on the pontoon and both props were new.
In either case, I took the wife out for a drive, and she liked it its quieter and it goes fast enough for her.
Now to go fix my broken trailer so I can get the pontoon out of the water!
I then put my old SS prop, which I was told was a 15P. That gave me 4800 RPM, but the speed appeared faster, and the motor was quieter. (No I do not have a GPS unit and the speedo on the boat reads between 15 and 18MPH). I figured that the SS prop was not a 15p, as it dropped the RPM by 1000 (and that?s with just one person)
Well I went and got a 13.75 /15P Al. prop from the marina, and put it on, The prop was a new one from Mercury). But when I went out, it only indicated 4800 RPM WOT and acted the same as my SS prop.
So I went from a 13P to a 15P, which you guys say should have dropped the RPM by 2*200 or around 400rpm, which would have placed the WOT RPM in the range of the motor. (Which I was told is 5000-5500).
I was told you should not allow the motor to lug, so I went back to the 14/13P and WOT RPM again indicated 5800, so I just won?t run WOT. (It does appear to run slower, but that may be a perception, as I have no way of accurately measuring speed ? I put a hand held GPS on my Christmas wish list.)
I guess this 200RPM per 1? pitch change does not apply for pontoons, as nothing else changing on the pontoon and both props were new.
In either case, I took the wife out for a drive, and she liked it its quieter and it goes fast enough for her.
Now to go fix my broken trailer so I can get the pontoon out of the water!