Re: prop diameter difference
houdini, #1, be very cautious not to exceed 2000RPM no-load...the engine can actually run away and turning the key off won't stop it.<br />I'm surprised the flywheel didn't depart the area, and most times on a run-away, the engine craters before you can disconnect the fuel supply.<br />The V4 crossflows run best at 5800RPM... less work, less fuel used at any RPM. Now, let's take into account I know you're thinking that the manual says other-wise, and why is this guy telling me different...well, we found out the engines started lasting MUCH longer, decarbs weren't revealing massive carbon build-up(coking is not the same, but the higher RPM helps prevent it due to the quality of todays gas not handling higher combustion temps)cylinders look better, and of course better fuel economy.<br />In all honesty, I would prop for 5800 with a normal load and consider 5500 as the minimum WOT.<br />I've ran my V6 crossflow to 6700RPM and it's rated at 4750-5750. I prop for 5800 minimum when I set up for everyday use.<br />Now, if your engine checks out, we can raise your RPM some by raisng the engine on the transom...lifting a bolt-hole or 2 can make quite a difference on most boats, some respond better than others...then, when we find the heigth it runs best with the prop you have, we can then go a step farther and change out props to a higher quality wheel designed to be run higher and maybe be able to go another hole up.<br />Keep us posted on what your shop tells you.<br /><br />OK, brownies, we're not apples to apples on the H5 vs. the 3-bld. The yammy prop has alot more blade area "per blade", and likely has more cup that the H5. remember rule #1...the lower the blade count, the higher the efficiency.<br />The 25 yammy was built for speed and the H5 was built for hole-shot.<br />Your rules DO apply if we stay with the same blade design.