[Kitto]

Well, we got the new (to us) boat out today for a quick turn on the lake. Wow, Mariahs are awesome. She is definately not the top of the line Mariah, but she's an original, bought and paid for and in great shape!! I'm definately going to be looking for a different prop. She topped out at about 4300 rpm at WOT and didn't get much over 40 mph. It came from California so I think elavation has something to do with it as she was slow getting out of the water as well for an 18 pitch prop. I have a 4 blade prop with the same pitch but I didn't get a chance to swap out today. Is there much difference in 1 degree pitch or should I be looking to go 20 or higher? Have a great weekend all and can't wait for summer!

[Z 202]

Sounds like you are a little over propped. You'd like to be in the 4600 to 4800rpm range at WOT. The 4 blade 18 might be OK, especially for when you're pulling as skier or a tube, as it gives better hole shot and quicker planing.

I run a 14"x19p stainless 3 blade with my 5.7L. It gives me good overall performance.

[Kitto]

So should I be going down in prop pitch or up? Since I'm at the lower end of the rpm range do I need to go down in pitch. Dang it, I'm all confused now. I was thinking I should be going up, but now that doesn't make sense to me. I think I'm a bit under powered with the 5.0 so I might have to go down in pitch. Seeking advise! Thanks, Kitto

[Z 202]

Do you know what gear ratio your Alpha has? If it came from a higher altitude it may be a 1.65:1 or even a 1.81:1 model. There is likely a stainless steel tag on one of the bolts securing the drive to the bellhousing. It should list the gear ratio of the drive. I believe you can also get this info by looking up your drive serial # on the mercruiser website.

If you know specifics (weight, WOT rpm, top speed and the drive ratio) you could try mercury's prop selector to see what it recommends.

Mercury Prop selector.