propped cups killing WOT rpms. what to do?

I have a 21 trophy with twin Force 85's.<br />21ft, 2350lbs, 2x85 outboard<br /><br />many years ago I plowed into a sandbar and absolutely destroyed one of the impellers. limping home on one engine the prop cavitated badly. All I could do was idle. I got home many hours later. If I had been in the gulf and there had been a storm then I could have been pushed towards mexico faster than I could make headway home. NOT acceptable.<br /><br />The engine had the big wing looking things. The propeller shop told me that they could cup my props and it would solve the problem. Well, it solved the limping too slowly problem but cut my top speed. WOT rpms immediately fell to 4500rpm and top speed dropped to under 35mph.<br /><br />Is there a way to have my cake and eat it too? <br />not drifting to mexico is more important than speed, but it sure would be nice to have the speed too. Is there some prop or other that can get back my top end without cavitating in single engine mode?

Re: propped cups killing WOT rpms. what to do?

Many available....what prop did they work on, and what RPM did you have before the props where damaged?

Re: propped cups killing WOT rpms. what to do?

thanks for reply.<br /><br />I drive like an old lady. I'm the guy who keeps safe following distance even in a traffic jam. I never went over 5000rpm because the book said 5500 was the max and I don't like to push machines to their limit. It had throttle left. I just never used it. So let's say they would go 5250 before.<br /><br />My props have three blades and are made from aluminum ... that is the full extent of my knowledge.<br /><br />mercury lists four props for use with engine<br />14x13, 13x17, 13x19, and 13x15 cupped. I have no idea what those numbers mean.<br /><br />how can I figure out which one I had?

Re: propped cups killing WOT rpms. what to do?

Somewhere on your old prop there are numbers...may be on either end where you may not be able to see them with it installed...<br />the numbers you list above are diameter and Pitch.13" diameter X 13, 15, 17 etc. pitch.<br />What year Model are your engines???