PROP QUESTION - Page 3

spiderjohn · 03-17-2010, 12:10 AM

I believe the change in rpm is about 200 rpm per 1" pitch change (inverse relationship - 1" increase in pitch = 200 rpm less in WOT performance). Material effects it as well (stiffer will decrease rpm more). 2000 rpm difference would still require a ton of change in pitch (10") which doesn't seem possible. If you should run a 21-23" I would be surprised if the pitch is actually as low as 13" on that drive. Is the prop too small in diameter as well? I would go to a shop with the prop in hand and the model of the engine and ask them to take a look. Sounds real weird.

Curtisimo81 · 03-17-2010, 07:57 AM

Quote:

sosmarine (3/16/2010)Possible that the gear ratio of the Outdrive is wrong for the motor too. Really would like to know what pitch the prop is first.

You may be right about the gear ratio, becuase when I got the boat the guy gave me two outdrives. The one that is on it isnt the one the boat came with. The one the boat came with is in my garage, because I need to have it rebuilt. But he said the one that is on there now came off of one with a 305 but anyone can say that........

sosmarine · 03-17-2010, 08:34 AM

There may be sticker on the upper left side of the drive with serial number and ratio.

Curtisimo81 · 03-18-2010, 10:17 PM

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

Telum Pisces · 03-19-2010, 06:17 AM

Quote:

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.

sosmarine · 03-19-2010, 07:59 AM

Agree. I would start with a 21 pitch and see what your RPM is at WOT then.

Sea Monkey · 03-20-2010, 07:08 PM

The OLE Spinnie Spin.

I have a 21p. SS. prop that came off of an Apha One Drive. I sent you a private message. Get in touch with me and we will try the 21p. out and see if it is what you need. I currently run a 17p. and have a 19p. for a backup. I turn more rpm with the 17, it put me rite in the sweet spot for my boat. I have a 224cu.in. 4 cyl. Mercruiser. I get better fuel range turning more RPM's than I do turning less. The 17p. freed up my motor and it doesn't bogg down at all with the 17p. in heavy seas nor do following seas gooble me up any more. It will feel like you have a new motor once you get the boat with the rite prop on it.

03-17-2010, 12:10 AM	#21
spiderjohn Senior Member Mingo Join Date: Feb 2008 Posts: 129	RE: PROP QUESTION I believe the change in rpm is about 200 rpm per 1" pitch change (inverse relationship - 1" increase in pitch = 200 rpm less in WOT performance). Material effects it as well (stiffer will decrease rpm more). 2000 rpm difference would still require a ton of change in pitch (10") which doesn't seem possible. If you should run a 21-23" I would be surprised if the pitch is actually as low as 13" on that drive. Is the prop too small in diameter as well? I would go to a shop with the prop in hand and the model of the engine and ask them to take a look. Sounds real weird.

03-17-2010, 08:34 AM	#23
sosmarine Senior Member Sailfish Join Date: Sep 2007 Location: Navarre/Town Center Posts: 1,856	RE: PROP QUESTION There may be sticker on the upper left side of the drive with serial number and ratio.

03-18-2010, 10:17 PM	#24
Curtisimo81 Senior Member Mingo Join Date: Nov 2007 Location: Pace,Fl Posts: 156	RE: PROP QUESTION 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

03-19-2010, 07:59 AM	#26
sosmarine Senior Member Sailfish Join Date: Sep 2007 Location: Navarre/Town Center Posts: 1,856	RE: PROP QUESTION Agree. I would start with a 21 pitch and see what your RPM is at WOT then.

03-20-2010, 07:08 PM	#27
Sea Monkey Senior Member Snapper Join Date: Dec 2008 Location: EAST MILTON Posts: 483	RE: PROP QUESTION The OLE Spinnie Spin. I have a 21p. SS. prop that came off of an Apha One Drive. I sent you a private message. Get in touch with me and we will try the 21p. out and see if it is what you need. I currently run a 17p. and have a 19p. for a backup. I turn more rpm with the 17, it put me rite in the sweet spot for my boat. I have a 224cu.in. 4 cyl. Mercruiser. I get better fuel range turning more RPM's than I do turning less. The 17p. freed up my motor and it doesn't bogg down at all with the 17p. in heavy seas nor do following seas gooble me up any more. It will feel like you have a new motor once you get the boat with the rite prop on it.

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