Prop size?

[AstroDiver]

I was talking to Carl Merritt on the factory tour. I told him that I was getting about 34 MPH @ 5700-5800 RPMs with a Suzuki 115 4 stroke. He said I should be doing 45 with that motor on my Lagic 186 with those RPMs.

My question is, how do I tell what size prop do I have? Where are "the numbers" on the prop?
If the boat would do faster would that improve my milage or make it worse? I have one of the fins attached to my motor to get it up on plane faster.

[MolarBoater]

Astro, you'll need to pull the prop off and the numbers should be imprinted on the back. The Suzuki has a beefed up lower unit so you get tons of torque and longevity but they may not be as fast as two strokes off the holeshot.
My Suk DF 140 has a 3 blade 14x20 Suzuki Stainles prop. Good for top end (@45) but probably too much pitch for pulling adult skiers at the lake all day (ok for one skier). You supposedly can get away with a little more pitch with stainless than you can with aluminum or composite.

[Putershark]

Originally Posted by MolarBoater

You supposedly can get away with a little more pitch with stainless than you can with aluminum or composite.

Due to the flex of other materials I would think (logically) it would be the other way around since the aluminum or composite (which flexes even less than aluminum) will lay back some under high torque / stress loads (launching) the SS prop will not flex as much thus you may not be able to run as much pitch. Now a SS Prop does not flex as much, thus you get better bite on the low end, and less of a chance of ventilation (pending angle of attack and # of blades of course) using Stainless than other materials.

Cavitation though is a different phoneomena altoghter and highly mistaken with ventilation. You then have many other factors that effect performance other than just simple pitch. Blade design, # of blades, etc. etc, and here is a good page that explains all of those design variables. http://www.miwheel.com/MIWheel/HowTo...pterm_main.htm

Choosing a correct prop (there is no perfect one) for you needs and load conditions is not a simple process. I do highly recommend though that before you shell out the cash for a Stainless model that you either run a Pro Pulse for testing / backup unit or get with a Mercury dealer who is on the demo prop program list.
http://sites.mercurymarine.com/porta..._schema=PORTAL

I would also think that for your combo that this page here
http://www.suzukimarine.com/boatbuil...mph190df90.php
would make for a good starting point performance wise to compare with

[AstroDiver]

Thanks MB. I'll take a look first chance I get.

I don't pull skiers and don't wish to. I tell people I'm not rigged for it or I make up any other excuse that I can come up with. I've offered to drag someone behind the boat, but they declined the offer.

I cruise, scuba dive, camp and now I'm taking up fishing on the boat.

[stingray502]

I agree that it takes a bunch of research to find something better, as far as props go. A 4 stroke will not get up aout of the hole like a 2 stroke will, so do not expect that kinda of performance. I would suggest researching and select another prop to test out, and buy an aluminum one to save your money.

Remember evrything affects how fast or how you boat might handle different from another one. An extra person, supplies, rough water, wind.

For instance I have dual batteries and a trolling motor and some other things that adds wieght so I know another 190 may run fatter than mine.

The most important thing is to stay in the proper rpm range for your motor!!