Prop advice

Gchaney · 05-07-2012, 11:00 PM

Ok finally got the boat in the water but with the bigger engine it over revs. First off as much info as I know. It is a mercruiser 260, in a 20 foot formula thunder bird, the current prop is a three blade 15-3/4 x 17 as I aproach wide open throtle it jist barely pegs the tach at 6000. As I understand wot rpm shoul be like 4400 to 4800. Does anyone have input on a new prop for this boat?

Thank you

drifterfisher · 05-07-2012, 11:07 PM

I've got a 15x 19 you could try...

Gchaney · 05-08-2012, 12:01 PM

That would probably be gelpfull at least kinda get a base line im pretty sure I am going to need to end up being around a 23 pitch.

Gchaney · 05-11-2012, 10:04 AM

Ok so I went up to the prop shop and picked up a cupped 21 pitch prop. We picked up about five miles an hour but we still peg the tach out over 6000. Am I going to be able to get that down to around 4800 with prop or am I going to have to change the gear ratio.

BlaineAtk · 09-07-2012, 08:39 PM

You should be able to get it down with the correct diameter and pitch. More pitch less rpm... I believe it is something like for every inch of pitch you go up, it drops rpm by 3-4 hundred. That's apprx but gives ya a starting point

eodryan · 09-08-2012, 12:55 AM

A lot of good info here: http://www.dansdiscountprops.com/propeller101.htm

sealark · 09-08-2012, 05:55 AM

Contact the boat manufacturer and ask them.

05-07-2012, 11:00 PM	#1
Gchaney Member Ruby Red Lip Join Date: Jul 2011 Posts: 43	Prop advice Ok finally got the boat in the water but with the bigger engine it over revs. First off as much info as I know. It is a mercruiser 260, in a 20 foot formula thunder bird, the current prop is a three blade 15-3/4 x 17 as I aproach wide open throtle it jist barely pegs the tach at 6000. As I understand wot rpm shoul be like 4400 to 4800. Does anyone have input on a new prop for this boat? Thank you

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05-07-2012, 11:07 PM	#2
drifterfisher Senior Member Sailfish Join Date: Oct 2009 Posts: 1,538	I've got a 15x 19 you could try...

05-08-2012, 12:01 PM	#3
Gchaney Member Ruby Red Lip Join Date: Jul 2011 Posts: 43	That would probably be gelpfull at least kinda get a base line im pretty sure I am going to need to end up being around a 23 pitch.

05-11-2012, 10:04 AM	#4
Gchaney Member Ruby Red Lip Join Date: Jul 2011 Posts: 43	Ok so I went up to the prop shop and picked up a cupped 21 pitch prop. We picked up about five miles an hour but we still peg the tach out over 6000. Am I going to be able to get that down to around 4800 with prop or am I going to have to change the gear ratio.

09-07-2012, 08:39 PM	#5
BlaineAtk Senior Member Mingo Join Date: Jun 2010 Posts: 534	You should be able to get it down with the correct diameter and pitch. More pitch less rpm... I believe it is something like for every inch of pitch you go up, it drops rpm by 3-4 hundred. That's apprx but gives ya a starting point

09-08-2012, 12:55 AM	#6
eodryan Senior Member Mingo Join Date: Mar 2009 Location: Mary Esther Posts: 139	A lot of good info here: http://www.dansdiscountprops.com/propeller101.htm

09-08-2012, 05:55 AM	#7
sealark Senior Member White Marlin Join Date: Sep 2007 Location: Pensacola, Sherman Cove Marina Posts: 2,948	Contact the boat manufacturer and ask them.

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