4 blade props

"hey guys, can someone help me

"hey guys, can someone help me chose the correct prop for my boat? I have a 1998 bayliner with a mercruiser 5.7 L Alpha 1 sterndrive. I want to put a 4 blade mercury on it. I am currently running a 3 blade 14.5 x 19 pitch. The rpm's are running at 4200. the owner's manual give optimum rpm's between 4200-4800. should I use a 14.5 x 18 pitch mercury 4 blade prop?
thanks, guys"

Is there something suave about

Is there something suave about a guy with a 4-blade prop?

I think you're already over-propped.
Go with less pitch and/or smaller diameter in a 3-blade.

"Rick,
What size boat is it,

"Rick,
What size boat is it, how much does it weigh and which prop are you currently running? Alum., stainless, Mirage, aftermarket, etc.

Finally, what are you trying to acheive with the new prop? Economy, top end, low end torque?

All of these factors will help determine what prop will best serve your needs.

Different props are specifically designed for different results. It's not just a matter of diameter and pitch."

"[b]"The rpm's are run

""The rpm's are running at 4200. the owner's manual give optimum rpm's between 4200-4800. should I use a 14.5 x 18 pitch mercury 4 blade prop?"

Ayuh,........ I'd start there........"

"Rick, to answer your question

"Rick, to answer your questions. I have a 1998 bayliner 20' length, wt. 2435 lbs. with a mercruiser 5.7L V8 Alpha 1 sterndrive. Currently has a mercury 3 blade alum. prop. 14.5 x 19 pitch. I am interested in a good all round prop for skiing, cruisering. I've done some research on the internet and have been told a 4 blade prop decreases gas usage, decreases plane time, increases speed, and lessens engine work (i.e. decreasing rpm's).
I've never owned a power boat until 3 weeks ago and am trying to learn. I look forward to some constructive input from someone who is willing to teach me a little about my boat. I thank you for your information/sugggestions and ask that other wise cracking comments be left to other postings where it may for better appreciated."

"Rick, Four blade props work

"Rick, Four blade props work well on outboards where you are jacking the engine up on the transom to reduce drag and gain speed. The extra blade gives you extra grip and reduces cavitation. They also work well on inboard boats where the diameter of the prop is limited due to shaft to hull clearance. The extra blade means extra grip, but it also means extra drag.

On an I/O where your drive is buried in the water, cavitation is usually not an issue and therefore a four blade will not benefit you.

A good three blade stainless prop will serve you well. Mercruiser's Quicksilver 19" should work good. The Mirage prop is a more refined, higher performance prop. It will give you little more speed but the longer blade configuration will cost you a little on the holeshot and you will loose a few WOT rpms as well. If you decide to get the Mirage, you may want to drop down to a 17".

The advantage of stainless over aluminum is that blade flex is greatly reduced meaning the prop keeps it's shape better under a load. Stainless will also hold a better cup than aluminum. The cup is the "hook" in the trailing edge of the prop which helps keep the water from washing off of the end of the prop and makes for a better grip.

If you have a relation ship with your local dealer, see if he has a prop you can try. He may well have a couple used new ones you can try and see what you are most satisfied with.

Welcome to the board and welcome to boating.

Rick"

"Thanks for the lesson, Rick.

"Thanks for the lesson, Rick. That helps alot."

My 2 cents: Reduce the pitch o

My 2 cents: Reduce the pitch of your present prop one inch (via a prop shop) and you'll be perfect!

Jeff

"i was told that 3 blade props

"i was told that 3 blade props are faster then 4 blades you really have to think about what you want to do ski or race (top speed) 3 blade bow lift 4 blade stearn lift they all so have more control in the water stainless makes a big difference i would look on ebay and fine a stainless prop 18 or 19 from the rpms you can't go any higher then 19 your rpms won't get to 42 any more if you do 17 would be great if your going to ski but your rpms are going to be alot higher then 42 rpms 19 will lower rpms better fuel milage try to fine a 16 or 17 4 blade that would give you the pull out of the water and the rmps should be about the same it all so makes a big difference how many people are on the boat full tank of gas or empty try used aluminum first much cheaper ask at the marines some times if you say you want to buy a new prop they will let you try some used props first or ebay i have a larson 23' with a 454 i have been trying to figure this out to i run a 25 4 blade but i can go 5 mph faster with a 26 3 blade and i still keep trying new props good luck "