another prop ?
 

Had a prop strike and was thinking of changing to a 4 blade prop.
I now have a 14 x 19p 3 blade, what would the equal be in a 4 blade also what brands ? This is for a 91 18' 4.3L . I dont know what my rpm were at WOT as the needle fell off my tach. But I could get here up to 50 with max trim on smooth water. Thanks for any sugestions

A 4 blade - 20"pitch should give you similar performance but you've done well to get to 50mph with a 19"pitch so it may be your best choice.

Any Brand you have had good luck with.

If you are staying with a 3 blade - 19"P aluminum then Michigan Wheel or Quicksilver. If you are going to a 3 or 4 blade - 19"P SS prop then Qucksilver Silverado or Thunderbolt, Stiletto Bay Pro or Michigan Wheel Apollo.
If you are going to increase your pitch you might want to consider buying & installing a set of Smart Tabs to get you on plane faster.

Thanks for the info

How do you size a prop to your boat? I just measured my new SS prop and its 15in Diameter. My high idle is a little under 4000. Merc spec is 4400-4800. The prop tool is showing me not to go over a 13.75 3 blade 21p. Im guessing that thats is where my 500 rpms are... Guess im out to find another prop. What are some of you guys running as far as diameter?

Unless you are at a 23 or 24 dropping down to a 21 will not do much in the way of increasing rpm. You may want to go down to a 19. Lower the pitch the higher the RPM. I have ran the same pitch with a 14" diameter and a 14.5" diameter and did not notice any difference in RPM, pitch seems to be the most important thing. Diameter does play a small role but not much IMO.

in my mariah owners manual, the previous owner wrote that it was sold with a 21p prop. When I bought it, it came to me with a 21p aluminum that measures 14.25. It was a little out of round so I found the mirage plus for a really good deal so I bought it thinking the Diameter was the same. The mirage is .75" larger than the aluminum. Im with you on less pitch more rpm, but in this case there is more surface area and a Hell of alot more than what the prop tool is recommending. Wouldnt that cause more drag?

I'm running a 14.25" diameter 21P and I get about 4400 RPM's. I was thinking the same as you - if I drop to 13.75" or 14", I should be able to get a couple hundred RPM's higher.

I don't have any experience running 2 props of the same pitch, different diameters. But I'd have to agree... you're trying to push a LOT more water with a bigger diameter.

I think it's the same idea as some cars reaching their top speed in 5th gear (out of 6). The wind resistance (or water, in our case) overcomes the gearing.

Let me know what you do, and what the outcome is. I'm still considering a change to a lower diameter just to squeeze out that additional 2 or 3 MPH.

well I picked up another prop today! Why doesnt everyone just wait intil I find what I want then I can sell the rest!! HAHAHA I am a tight ass though and usually dont buy anything UNLESS I can get a deal on it. The prop I bought today is a 19p alluminum for $50. If it runs good Ill get me a SS 19, I really just think that its going to Slow my ROW. Yea the rpms will be there but will probably top me out at 40mph. Im going to look for a 14x21p

Indy- Is your prop a 4 blade?