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Gear ratio on merc 2.0

Stevenlockamy

Stevenlockamy

Active member
I am trying to find out what gear ratio I have on my mercury 2.0 black max? I'm pretty sure it's a 1.87? If it is will going to a 2.1 ratio help top speed? With my motor setup now prop shaft even with hull,8in jack plate and 24p small ear chopper that i cupped and worked myself I'm running 70mph (GPS) any feed back would help guys I'm lost on this gear ratio thing!
 
Stevenlockamy said:
I am trying to find out what gear ratio I have on my mercury 2.0 black max? I'm pretty sure it's a 1.87? If it is will going to a 2.1 ratio help top speed? With my motor setup now prop shaft even with hull,8in jack plate and 24p small ear chopper that i cupped and worked myself I'm running 70mph (GPS) any feed back would help guys I'm lost on this gear ratio thing!
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Most of the 150's I have encountered were 2:1 ratio. The 2.4L mercs were 1.87:1.

What rpm are you turning?

If you do have a 1.87 and change to a 2:1 lower, you would need to go up in pitch or turn higher rpm to run the same speed.
 
Stevenlockamy said:
Was turning 6,400 at 63mph after I worked the prop I got it down to 6,000 rpm at 70
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The numbers before you worked the prop lead me to believe you have a 2:1.

6400 rpm with 2:1 ratio, 63 mph, and 24P prop nets you 13% slip. If you had a 1.87 lower, you would be at 19% slip which does not sound right to me.
 
although your numbers after the prop work leads to 1.87. It is so hard to tell without a definite prop pitch.

Have you plugged your serial numbers into the merc parts site? I think the number on the mid will tell you the gear ratio.
 
I have tried but no luck the problem is motor is a mix of mariner and merc I know they are same but my gear case is off my blown 2.0 motor and the tag is not on bracket so I'm kinda lost! So would the 1:87 ratio be better? (A943061) is on my new mid section tag now I have tried looking number up but no luck?!
 
This guy has some great merc info all in one page. http://www.biggerhammer.net/mercury/ check it.

IF the lower came off of a 150 carb engine, I would bet 20 bucks it is a 2:1.

The numbers you posted after the prop work look like you stretched that prop out to act as almost a 27P.

I would hustle up a 26P chopper and run it stock. See where it is at and then work that one just a bit. It would be cheaper than a new used lower.
 
I have a 26p big ear chopper all stock and the boat ran 70 at 5,600 5,800 rpm but with slight over trim with my worked 24p I run 70 slightly over neutral trim.. And with 1 person in boat rpm drop to around 5,400 rpm with the 26p so I let it go to wired on this sight. I think my 24p now is going to be my best prop! Just trying to get more speed without changing props( I love my 24p)
 
Stevenlockamy said:
I have a 26p big ear chopper all stock and the boat ran 70 at 5,600 5,800 rpm but with slight over trim with my worked 24p I run 70 slightly over neutral trim.. And with 1 person in boat rpm drop to around 5,400 rpm with the 26p so I let it go to wired on this sight. I think my 24p now is going to be my best prop! Just trying to get more speed without changing props( I love my 24p)
Click to expand...

Man your numbers are all over. However, The numbers from the 26 chopper look like a 1.87 as do the numbers from the worked prop.

70 is real good from a 150.

I like this calculator. http://www.rbbi.com/folders/prop/propcalc.htm
 
Man thanks a lot for the prop calculator sight! It looks like 1:87 with my 24p? I guess I'm doing good for what I have!? And the motor is definitely a frankenmerc someone has upped the compression to 145psi and 2.5 tuner and other stuff! That's how I bought it so really don't want to tear into a motor I have no idea what the person before me did!
 
Just turn the motor over ten times by hand and count how many revolutions the prop makes. If its 5 you have a 2:1 lower. If its close to 5 1/2 you have a 1.87 lower.

My 1.87 lower will turn a slightly worked 26 chopper 82.8 MPH bouncing off the rev limiter at 6750 ( before I melted a piston with an LEAN A17 box ) . That would be equivalent to your 5600/70 MPH if scaled up. The 26's are pretty efficient. The 22's...not so much. Mine twists my 22 big ear chopper 7000 RPM at 60 MPH. Its my last ditch spare.
 
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