I have a 1976 merc 150, I would like to know what size prop I can use, currently I have a 19p I beleive it is 13.25. I would like to pull skiers, do I need a higher pitch-23? or do I go lower, and how high or low can I go?
Hello,<br /><br />You should first of all make sure you have a working tachometer to determine your current Wide Open Throttle RPMs with the current 19 prop. The motor should be propped so that it will make 5500 RPMs with a normal load. If you can't make between the suggested 5300-5800 range then you need to drop a pitch size to 17 and check the RPMs. Every 2" drop in pitch is said to increase top end RPM by 300-400 RPMs (I think). For pulling skiers, you will likely need a smaller pitch prop (17 or 15). It all depends on being able to get into that RPM range without making the motor lug at lower RPMs- which will cause pinging and detonation with destructive consequences. Every pitch you go up will decrease RPMs. The lower pitch gives more hole shot but sacrifices top end. Lowering pitch prop is similar to gearing the transmission down in a car to climb hills. I would do a search for prop sizes and specifics about that motor in the Merc forum related to inline RPM range and detonation. <br />Also the FAQ section may have some info as well.<br />Hope this helps.
