The original prop...
for the Hunter 33, Yanmar 2QM15 engine, was a 14x12 in bronze, not brass. With that propeller, and a normally loaded boat, clean bottom, etc, you should, in fact be able to achieve your rated RPM of 3000. Or, at least, I did so, for years. But, there is not much margin, and when the engine becomes more loaded (bigger alternator, strong headwind, or exceptionally heavy payload), that little 2QM15 just won't quite spin at 3000. I recently resorted to taking an inch out of the pitch of my prop, which is now a 14x11. The prop shop said that each inch would affect the RPM by about 200. My engine now achieves a maximum RPM of 2800-2950, depending on the already mentioned factors, so I kind of wish I had taken out two inches of pitch, giving me a 14x10. By the way, I DO have a bigger alternator, and Casual Water is probably about an inch or two down on her lines, the result of sixteen years of living aboard. What I found very interesting is that she seemed not to loose an iota of speed, for the corresponding RPM, with the lower pitched prop. I was expecting to have to run slightly higher RPM's, but such has not been the case. Everything is a bit smoother, too. So, I guess I would thoroughly endorse the idea of anyone who is intending to actively cruise the 33 with the 2QM15 to seriously consider de-pitching the prop at least one, if not two inches. It is worth noting that this engine was sized in a period when auxiliary engines were exactly that....auxiliaries. The standards of that era suggested much smaller engines than are now typically installed. Using the current formulas for sizing engines, you will arrive at a considerably larger engine than you have. But, no worries, the 33 moves quite nicely with the 2QM15, but it has almost no margin in reserve. So consider a bit less pitch, and you will get to the rated speed, which is better for the engine. Good luck.
