Worn props and decreasing diameter

[sknkna]

I am currently running a 2001 115hp Johnson on my 19ft center console Sea Fox the recommended WOT is 5250-5750. I have a 14X19p factory prop and WOT is coming in at 6100 and my top speed is 36-37mph. When it was new (3 seasons ago) I could get it going 40 to 41mph and WOT was about 5800. Now the prop is slightly worn and looks like just the paint has been sanded off the blade tips but is other wise it’s in good shape.<br /><br />My questions are:<br /><br />1. Is the slightly worn prop the most likely problem with my performance? Someone told me that an engine’s WOT may change after it is thoroughly broken in.<br />2. I am thinking about going to a SS or possibly a higher performance Aluminum like a Turning Point Hustler. I cant decide between 13-1/4 Dia. 19 Pitch and a 13-1/4 Dia. 21 Pitch. What would be your advice?<br />3. I understand the effect of changing Pitch but what will be the impact of decreasing the diameter<br /><br />Any help would be appreciated<br />Thanks

 

[OBJ]

Re: Worn props and decreasing diameter

Hey SK.....welcome to the forum...<br /><br />Three seasons ago is a long time for a two stroke. When was the last time you had a tune up including a decarb? The WOT will sag a little with time and running. You will want to stay in the recommended WOT rpm range else you risk a blown head. 6100 seems a might high to me.<br /><br />Do a decarb, put some fresh spark plugs in it. If you think the prop needs a tune up (rebuilt or re-cupped) then do so.<br /><br />SS props will give you better performance and a little more rpm. They will also clean yer' wallet out.<br /><br />Go for a complete tune up first with yer favorite mech. Get compression readings also and follow up on them every year. Don't forget about getting the engine decarbed. <br /><br />Keep us posted as to your progress. Thanks.

 

[Mod2]

Re: Worn props and decreasing diameter

Moving to Johnson/Evinrude Troubles forum.

 

[Dhadley]

Re: Worn props and decreasing diameter

Yes your correct. Wearing down the prop, both in diameter and therefore blade area will result in decreased bite (less speed) and higher rpm's (less efficient).<br /><br />Your original set up sounded pretty good as far as rpm's go but was about 25% slip. Thats not good.<br /><br />We have had great success with Stilettos on that boat if you dont have a jackplate and Turbos if you do. I think you can do a little better on speed if we cut down the slip %.<br /><br />While 6100 will not harm your motor at all its over 30% slip now. That hurts the ol wallet.<br /><br />Good luck!