Propping my Jon boat

I have a 1995 40 hp mercury on the back of my 1860 aluminum Jon boat(weight is about 500 lbs.). I use this boat to run the river and nothing else. Except for my seat,the fuel tank,and a couple of batteries this boat is empty. I currently have a 12 pitch prop but it's time for a new one. I want a stainless replacement and figured if I'm going to invest the money maybe I should do some research to see if I can improve my performance. Is it possible to pick a "off the shelf" replacement to improve my top end without knowing my RPM's??? my brother has the same identical boat and motor and we run nose to nose. I was hoping to have the edge after replacing the prop if possible. Any suggestions or help would be appreciated.<br />Thanks, Ed

Re: Propping my Jon boat

The worst thing you can do to a boat motor is run the wrong prop. If you are willing to invest in a stainless prop, you should also invest into a tach and run your motor at the proper rpm range. If memory serves me correct, max rpm is 5500. You want your motor to turn around 5300 for max performance and fuel mileage. Here in my shop, the number 1 cause of powerhead failure is a badly propped engine.

Re: Propping my Jon boat

Thanks for the words of wisdom OMCtech that's exactly why I posted here to avoid any stupid mistakes. Another question: Does anyone know the stainless equivalent for a mercury prop # 48 73134 A40 12P....I like to do some initial comparison shopping utilizing the internet. If anybody is an online distributor I'm open for suggestions.<br />Thanks for everybodys help!<br />Ed

Re: Propping my Jon boat

Ed, you can look at iboats "propeller" section, and they show a table that lists some numbers. Also do an internet search on "outboard propeller" and you will get some good sites to check. Go to Mercury's web site, and it will help to recommend the correct pitch.<br /><br />You really do need a tach though - it will help you for tune up checks too. Do like I do, I just plug it into the connector for testing, and leave it in the garage the rest of the time.<br /><br />My gut feel tells me you should be able to go up an inch or two in pitch, because I have a slightly heavier boat with a 50 HP on it, and it looks like I'm going to be with a 16 or 17 pitch when I get done with it.<br /><br />I ended up getting with a prop shop, and the owner is going to go with me, and try all of his props, just to see which one is best.