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Old 02-25-2019, 11:15 AM   #1
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Default prop size 1993 2300SCR?

I know nothing about props but i do know that the prop on my 1993 2300SCR Alpha one, gen 2 4.3LX 180HP is worn out and im also looking for a prop that makes the boat 'sway' less at low speeds.

Most of the paint is gone and it has dents and the blades are even warped in some areas.

But... when i went to a site to buy a new one they asked me what size prop i have so they can advise me on a replacement.

how can find out?


I think the current prop is the one that came with the boat when it was manufactured.

any idea?
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Old 02-25-2019, 11:50 AM   #2
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First a prop change is not going to improve slow speed wander worth noting.

All single screw boats have this and the Alpha has a trim tab anode just above the prop that you can adjust the angle on to help counter the props torque.

Also check for excessive play of the outdrive; see if you can move it side to side without the wheel turning. If so the swivel shaft is probably worn.

Your prop doesn't look to bad and a prop shop can recondition it and also measure it to let you know its diameter and pitch.

Some props are marked on the outside of the hub and other on the back of the hub that is currently covered buy the thrust washer and nut.
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Old 02-25-2019, 01:14 PM   #3
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I can't see any damage to the prop blade in the image, aside from some missing paint.

You would only replace the prop for a limited number of conditions:

1) Prop is damaged and is stainless steel
2) Prop is steel and damaged beyond repair
3) Boat is overpropped and you need to reduce pitch or number of blades.
4) Boat is underpropped and you need to increase pitch or number of blades.

As stated (above) 'bow wander' is partly a result of physics and is worsened by oversteering. The frustration is a result of expectations (a boat will never handle like an automobile).
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Old 02-25-2019, 01:25 PM   #4
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Quote:
Originally Posted by mmwjr View Post
All single screw boats have this and the Alpha has a trim tab anode just above the prop that you can adjust the angle on to help counter the props torque.
this is interesting...

mine is flat and i did a search and see that there are also fin-shaped tail annodes that, if adjusted correctly, seem to be made explicitly for tackeling the 'wander' problem

this guy really explains how it works pretty good:


i think ill get one of those and see if the wander gets reduced a bit.


thanks (mjjwjr and shrew) about the info about the prop.
i think ill leave it in that case. perhaps just give it a bit of anti corrosive spraypaint.
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Old 02-25-2019, 10:00 PM   #5
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Crus, to reduce low speed wander, try trimming the drive out a little more. This will reduce the effect of prop thrust, which is a good thing, and may get the prop/sterndrive into calmer water.
When correcting for wander, fight your instincts and put in about half of the correction you think you need. Small corrections are the way to go.
For your prop, have you looked down inside the prop from directly astern? Sometime the prop size is in there. I imagine you have already looked all over the prop, but usually the size is stamped somewhere.
A four bladed prop will help with low speed control and is excellent for water sports.
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Old 02-28-2019, 10:06 AM   #6
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i found these numbers on the prop... but i think its not related to size and pitch... or is it?


also, i wanted to install the anode in the propshaft but it doesnt fit although i got the alpha one, gen 2 set. the other anodes did fit.

is this perhaps a non standard shaft?
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Old 02-28-2019, 11:08 AM   #7
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The "15P" means 15 pitch.
You can determine your prop diameter by measuring from center of prop to tip of a blade. It might be easier to measure while prop is mounted and use center of prop shaft as starting point.
What is your RPM at WOT?
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Old 02-28-2019, 11:23 AM   #8
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Google that part number and you should find the manufacture and specs. As mentioned the 15P is the pitch.

You need to remove the thrust washer (round disk) from the prop shaft then the anode will go on. It just pulls off but may take some force as it looks like its been a long time since the shaft had new grease applied.
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Old 02-28-2019, 01:36 PM   #9
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78116A15 15P

It's a Mercury Black Max 15.25" x 15 Pitch 3 blade prop.

A15 = Alpha 15 inch
15P = 15 inches of Pitch.

Pitch would indicate the number of inches of forward movement made if the prop made a full revolution through a solid medium.
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Old 02-28-2019, 02:27 PM   #10
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Take it to a prop shop and have it tuned up.. Not expensive.
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