It's a Alpha,traded in my stainless 21p for 3 repairs. The prop is aluminum. Serial #'S ,Not sure I can find them. Checked yesterday,no numbers. Love the top end that's why I'm entertaining a 4 blade/lower pitch etc. I'm pretty sure because of the top end gearing,a 15p might be the answer?. The boat is a 187 Scorpion Chris Craft/1986. Little waterlogged,maybe/maybe not. The long snout is what I think the problem is. You put 3or4 guys,coolers,big tackle boxes etc. sitting from middle to back,that,s a lot of rear drag. Will try iboats anyway. Thanks guys for your input.