still looking for advice on what size and pitch prop i need

[mrgixser]

please give me some advice on what size and pitch prop would be best suited for my pro craft. all of the info about my boat is in this post. please help i need a new prop and not sure what to get.<br /><br />the name of my other post <br /><br />1979 115hp Evinrude, whats the max R.P.M?

 

[Silvertip]

Re: still looking for advice on what size and pitch prop i need

You aren't going to get any suggestions because we can't see your boat and you don't seem to understand the basic parts of the engine and the boat. There were several answers in your other post about how you achieve 5800 RPM. It has nothing to do with the throttle adjustment. Several things affect this. Either the engine is not performing up to par in which case a full tune-up is necessary to ensure that. If it still fails to reach 5800 RPM at wide open throttle you need to check engine mounting height. The boat hull may simply not be performing with the current prop. The cavitation (or proper term anti-ventilation plate) is the flat plate just above the prop. That must be even with or slightly above the bottom of the boat. If that's ok, then you need to know what the existing prop diameter and pitch are. Since your engine will not reach 5800 RPM a prop with less pitch is required. This will improve hole shot and raise engine RPM. If your engine was overreving (higher than 5800) you would install a prop with more pitch. Before spending money on props, make sure everything else is in order. Do the simple stuff first.

 

[mrgixser]

Re: still looking for advice on what size and pitch prop i need

i think i,m getting the picture now. the anti ventilation plate is a couple of inches above the bottom of the boat, going by what you said this seems to be about right. also the motor is freshly tuned and runs perfect. so i need to go with a prop with less of a pitch (correct)? i can take the prop to the dealer with me and find out what pitch it is. all that i need to know now is how much less of a pitch do i need to make a difference,without over doing it? i need to pick up atleast an extra 7,000 rpm,s<br /><br />thanx for being patient with a beginner, and all of the advice is much appreciated!

 

[ezeke]

Re: still looking for advice on what size and pitch prop i need

The propeller number that you previously gave is for an OMC 21 pitch 3 blade aluminum standard (right hand) prop. Click the "propellers" link at the top of this page. You can then enter your number for confirmation. Enter your motor description and get a list of options. <br /><br />You meant 1,000 RPM, right?<br /><br />There are also some links at the bottom of that page that will help you with information.<br /><br />It is important to test your current RPM at differing trim levels. If you still have the 1/2 steel stop rod (thrust rod) in place at the bottom of the bracket, try moving it in 1 hole from the current position and then taking a reading, then repeat out 1 hole.

 

[mrgixser]

Re: still looking for advice on what size and pitch prop i need

oops! my fault i meant 700 rpm,s

 

[JB]

Re: still looking for advice on what size and pitch prop i need

You need to ask this question in the Prop Forum, Dan.<br /><br />I will move it for you.