Attn Gear Box Guru's

[ToonGuy]

OK I got a hot minute to look at the Mercs last night, here is what I found. The port motor's prop rotates 1 time for approx. 1-7/8 rotations of the crank shaft. The Starboard motor is exactly 1 prop rotation for 2 full crank shaft rotations. My questions now are:

How much of a difference in RPMs do you think that would make? I'm approx. 600 RPMs difference between the two all the way across the board.

How would I find out exactly how many ratios were available for these things?

[curtiscapk]

Ty,

this place is fairly knowledgeable. I have never called them but they have a lot of info on their site. They list different ratio's and lengths for every year.


http://www.maxrules.com/fixmercgearcase.html

[ToonGuy]

That place is a great site, unfortunately I could only find ratios up to model year 1988...

[curtiscapk]

Dang I just saw this


Mercury ceased publishing this information after the 1996 model year.
There is no way to find the model year of motors with significantly higher
serial numbers than listed in these guides.
There is NO serial-to-year cross-reference chart for 1997 and later motors.
Mercury has never used model years for anything other than "sales tools" in dealerships.
We WILL need your serial number to look up correct parts.

but the sell lowers for 2006 and up... maybe a phone call wouldn't hurt?

[ToonGuy]

After further review: I'm an idiot. They are the same. And after some more research, and I could be totally wrong on this too, it appears all 3.0L Mercs used a 1.75:1 ratio lower. The 3.0s did not have the options the 2.5s had. Back to the drawing board....

[Bamby]

May be relevant if it actually applies to your motor. In this drawing it appears there are 2 gear sets available a 1.75 and 1.62. So maybe there is a chance that you do have motors with two different gear ratios.