PROP QUESTION

Curtisimo81 · 03-15-2010, 10:18 PM

How you all doing tonight? I bought a boat last summer and I'm worried about it b/c it will 7k at WOT. Its a 305 mercruiser with an alpha 1 outdrive. I have only ran it to 7 once trying to see if the prop had the right pitch. Well obviously its doesn't!!! Max rpm should be around 5400, i normally cruise around 3200. My question is which way do I need to go with the prop to get the rpm to come down and how will that affect the performace of the boat. I mean it gets on plane pretty good. Its a 22ft thompson carrera, cuddy cabin. What are your opinions on this?

SUNDAY-FUNDAY · 03-15-2010, 10:20 PM

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.

Telum Pisces · 03-15-2010, 10:45 PM

Quote:

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.

Curtisimo81 · 03-15-2010, 10:54 PM

Quote:

Telum Pisces (3/15/2010)

Quote:

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 100. 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.

I would agree with the blowing of the motor except for thefact that I havent ran over 4k because, being and automotive tech and my motor is basically a car motor with some modifications, i know what kind of damage comes can come from over reving. By the way the rpm gauge is pretty much on I tested it with another one.

SUNDAY-FUNDAY · 03-15-2010, 11:02 PM

Quote:

Telum Pisces (3/15/2010)

Quote:

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 100. 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.

i was thinking the same thing. but, didn't want to say "you need 15 degrees more prop." what pitch, and how many blades, are you running now?

Brandy · 03-15-2010, 11:03 PM

what is your speed at rpm

Brandy · 03-15-2010, 11:03 PM

What is the spped at rpm?

Telum Pisces · 03-15-2010, 11:07 PM

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.

Curtisimo81 · 03-15-2010, 11:12 PM

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..

Curtisimo81 · 03-15-2010, 11:16 PM

Here is a picture of the boat. I mean at 30mph cruising I think thats pretty decent.

03-15-2010, 10:18 PM	#1
Curtisimo81 Senior Member Mingo Join Date: Nov 2007 Location: Pace,Fl Posts: 154	PROP QUESTION How you all doing tonight? I bought a boat last summer and I'm worried about it b/c it will 7k at WOT. Its a 305 mercruiser with an alpha 1 outdrive. I have only ran it to 7 once trying to see if the prop had the right pitch. Well obviously its doesn't!!! Max rpm should be around 5400, i normally cruise around 3200. My question is which way do I need to go with the prop to get the rpm to come down and how will that affect the performace of the boat. I mean it gets on plane pretty good. Its a 22ft thompson carrera, cuddy cabin. What are your opinions on this?

03-15-2010, 10:20 PM	#2
SUNDAY-FUNDAY Senior Member Trigger Join Date: Apr 2008 Location: Biloxi MS Posts: 371	RE: PROP QUESTION 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.

03-15-2010, 11:03 PM	#6
Brandy Senior Member Grouper Join Date: Sep 2007 Location: Gulf Breeze Posts: 782	RE: PROP QUESTION what is your speed at rpm

03-15-2010, 11:03 PM	#7
Brandy Senior Member Grouper Join Date: Sep 2007 Location: Gulf Breeze Posts: 782	RE: PROP QUESTION What is the spped at rpm?

03-15-2010, 11:07 PM	#8
Telum Pisces Senior Member Blue Marlin Join Date: Sep 2007 Posts: 4,608	RE: PROP QUESTION 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.

03-15-2010, 11:12 PM	#9
Curtisimo81 Senior Member Mingo Join Date: Nov 2007 Location: Pace,Fl Posts: 154	RE: PROP QUESTION 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..

03-15-2010, 11:16 PM	#10
Curtisimo81 Senior Member Mingo Join Date: Nov 2007 Location: Pace,Fl Posts: 154	RE: PROP QUESTION Here is a picture of the boat. I mean at 30mph cruising I think thats pretty decent.

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