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Old 03-15-2014, 08:34 AM   #1
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Default 2100SC3 propeller advice

I have an MPI 5.0 260 bhp in my 2100SC3 - WOT (5100 revs) gives me about 51mph using a 14 5/8 x 17p 4 blade ss prop. It comes onto the plane at around 16mph due to smart tabs which are great.

I am looking for greater economy and top end speed. Therefore need to go to 19P ss prop, but not sure whether 3 or 4 blade.

Can anyone advise and does anyone have any performance stats they can share even if first hand.

BTW - I went on the Mercruiser prop sizing website and one of the pieces of information they wanted was the Alpha drive gear ratio where they offer 3 ratios to choose from: 1.47, 1.62 0r 1.81. Does anyone know which comes as standard or how I can find out? Thanks for al your help.

Regards

Ian
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Old 03-15-2014, 11:48 AM   #2
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Ian I am not a prop expert but going from a 3 to 4 blade prop inaddition to increasing pitch may be to large of a change for all around performance. I would suggest one or the other.

Hopefully others with a similar setup will tell you what they are running.

If you can find the S/N of the outdrive you should be able to look up which gear ratio it has.
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Old 03-15-2014, 03:32 PM   #3
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Call these guys. They are the pros!

http://hillmarine.com/?gclid=CIi_55vulL0CFTBgMgods3wAOg
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Old 03-16-2014, 02:13 PM   #4
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I have a 2100 SRB, I run a 4 blade stainless 21P with a 5.7 and top out at 59MPH.... Just for reference
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Old 03-16-2014, 03:27 PM   #5
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Darren what is the HP of your 5.7?
The OP has a 5.0 rated at 260 HP.
I am thinking he would need to drop down 1 pitch.
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Old 06-04-2014, 08:54 PM   #6
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Oneradride, what is your max RPM's with that 4 blade? I am trying to to figure out my prop also for my 2100 SR with a 5.7L and I was thinking of going down to a 19p 4 blade..

Here is what I have going on..
http://www.maxumownersclub.com/forum...rch!!-Any-help
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Old 06-05-2014, 02:20 PM   #7
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Quote:
Originally Posted by Islandhopper View Post
Oneradride, what is your max RPM's with that 4 blade? I am trying to to figure out my prop also for my 2100 SR with a 5.7L and I was thinking of going down to a 19p 4 blade..

Here is what I have going on..
http://www.maxumownersclub.com/forum...rch!!-Any-help
I would not suggest going by what others are running. There are a lot of variables and it is best to determine what the actual Max RPM is of the boat being re-propped.
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Old 06-05-2014, 10:04 PM   #8
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I have a larger cam and different heads my 5.7 puts out about 310 HP. anything larger and the overlap in the cam would not work well with the wet exhaust..... 5100 RPM trimmed just right.
I've added about 300.00 lbs of additional permanent, stationary equipment (mostly stereo stuff and batteries) and still can get her to 55 MPH with no issue, the launch is NOT great unless there are a few in the front.. may be looking at trim tabs or something in the future.

My cousin races sprint cars and has a few led valve cover castings (they fill valve covers full of lead and bolt the casting onto the cars for weight... I may place a few in the bow just to see what happens sometime

EDIT - Also much over 300 HP and your just asking to grenade the alpha drive.
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