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SUNDAY-FUNDAY (3/15/2010)higher pitch will bring your rpms down, as well as giving you much more top end speed. being 2 grand over MAX i'd say you need at least 3 degrees more pitch.

Typically one degree in pitch will change the rpm's by 150-200. So he would need a lot more than 3 degrees of pitch. My guess is the RPM gauge is not working if it is showing that much over the max RPM and you have not blown the motor yet.

 

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You want to go just past your max RPM (by 100-150 rpm)with no load and a light gas tank in the boat. You said what type of motor, but what type of boat is it? And what type of pitch is the prop right now? Then we can give you a better guestimate of what you need. But if you want to be sure without buying all kinds of props to test it out, go down to either Accu Prop or the Prop Shop. They'll be able to hook it up right the first time. And if not, they will swap it out with no problem till it gets right.

 

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Curtisimo81 (3/15/2010)Its a 22ft thompson carerra, its in the pic under my name. I dont know what the pitch is at right now, but its 3blade and at 3200-3400 i cruise between 27mph and 30mph just depending on the water. I know the speed is pretty close b/c thats on my gps. I wish i knew the pitch now. But this is something I would like to get fixed pretty quick..

It should be stamped either on the barrel of the prop or on inside portion barrel maybe by the splines. It's stamped somewhere on there.

I just do not know how that boat could be turning 7K RPM's unless there is a john boat propon there????????????? And if that was the case, it would not be going faster than about 10mph. Are you sure that your max RPM's are hitting 7000?

On a side note. If that's a 22' boat, that's a lot of boat for a single axle trailer.

 

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Curtisimo81 (3/15/2010)

bonita dan (3/15/2010)7 grand is way too much for a Mercruiser engine! Prop diameter and pitch are keys to getting your boat running the most fuel efficient and best speed. Seems to me like your under-proped.

I know... I guess i just need to take the prop off and bring it to the prop shop. I can napa to pick it up for me and take it over there. What do you all think it will run to have it the pitch adjusticed on it?

This is just a guess. And it's all a guess untill you take it to an expert and let them tell you what you need.

But I just ran some info through a prop calculator using your boat and motor combo and it spits out a 14-1/4 x 21 prop if you load it down a good bit. Or a 14-1/4 x 23 for top end speed. These are both 3 blad stainless props. If you want a little more hole shot and low end pulling power, drop the pitch by one degree in order to go to a 4 blade prop.

 

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Curtisimo81 (3/18/2010)I looked on my outdrive no numbers :boo but my prop did havethree different number, the first is 4b 93272 a4 15p and CM3673 and C1960 Have no clue as to what they mean. If someone could help me decifer these that would be great. Thank you agian for all the great info you all have given me about this situation Im in with this boat

That is a 15 pitch prop.(15p) I would estimate you to need either a 21 or 23 pitch prop.