4 blade prop??

[THEFERMANATOR]

Originally Posted by Destroyer

Once you get your engine height dialed in here are some things to consider:

4 blade props will give you a better hole shot and the least vibration, but at the cost of top end. (The more blades in the water, the more drag/friction on your engine.) A 2 blade prop gives the best high end, but at the cost of more vibration and poorer low end, which is why most people run 3 blade props. They're a good compromise between the 2 blade and the 4 blade props.

Right now you're running a 19P stainless prop. The equivlant prop in Alum would be a 21 pitch. As a general rule of thumb you drop 2 inches of pitch when you switch from Alum to SS...so if you're going from SS to Alum you add 2" to your thinking. So if you're thinking about dropping to a 4 blade 17P, the same prop in Alum would be a 19P. To my way of thinking, that's too much prop for a 150 engine. I think that the first prop I'd try would be a 17P Alum for a baseline, and then work from there once i saw what my RPMs were.

Careful with changing pitches when going from stainless to aluminum. New aluminum props are now being built slightly different to account for this. I've done a few swaps recently, and actually found teh WOT RPM's went down some with an aluminum of equal pitch because it wasn't as fast on the top end due to the extra blade thickness. Get the engine height correct first, but also keep in mind engine height may need to be changed according to which prop you run as some like to surface whereas others need to be buried. And find a prop shop that will work with you. I know my local prop shop will swap out props for a small fee if it isn't the right one so long as it is still in new condition(no scratches or chips in it, or cavitation burns).