how do i find out my gear ratio?
 

2002 bravo one how do i find out what gears are in it? trying to calculate prop slip.

thanks

On the decal on the port side.

And if your dacal is missing, find your serial number and call merc.

Chewy,
More than likely it is a 1.5 or 1.36. What numbers do you have to work with. You can get a good idea by what speed and rpm you are running.
RPM x Pitch/1584=100% efficiency for 1.5 gears.
RPM x Pitch/1436.16=100% efficiency for 1.36 gears.
Start by multipling the answer by .90 to give you 10%slip. That should get you close to real numbers. At least close enough to figure out your gear ratio.
If that doesnt work, you can pull the top cap and count teeth, although that is easier said than done. Best way is to pull the input shaft and count..
Do the math if you cant get a serial number to check.. see where that takes you.
Hope that helps.
Dick

Pull the drive, give the input shaft one revolution, and see how far round the drive shaft turns.

Wouldn't it be alot easier to pull the top cap and count the teeth? Again, if he can find the serial no. and just call merc, that would be the easiest.

I was told if you rotate the input shaft 15 times the prop shaft would turn 10 times making it 1.50.1 That's what I did. JOHN SR

Put a piece of tape on one of the prop blades.

Put a chalk mark on your motor's balancer pulley.
Match up a socket and extension to the crank bolt.
Hand your wife a ratchet and tell her to ratchet over the motor exactly ten revolutions.

Sit in a lawn chair behind the boat (assuming it's on a trailer) with a beer in your hand. Count the number of complete rotations, and estimate the partial turn and add them together.

At ten motor revolutions, the prop will turn 6 2/3 revolutions for a 1.50:1 ratio.
At ten motor revolutions, the prop will turn 7 1/3 revolutions for a 1.36:1 ratio.
...and so on.

MC

How many beers did it take get the 10 revs out of the wife? :)

Oh, I don't use the wife method. Too dangerous.

I put my camcorder on the lawn chair and record the propshaft while I spin the motor over with the starter and shout the number of motor revolutions.

Be sure to use water muffs to keep from killing your impeller, and pull the kill switch to keep the motor from trying to start. Use a handheld switch and jump it to the starter solenoid.

Start the camcorder, hop in the boat where you can see the balancer. Start cranking - shout 1, 2, 3, 4, 5 so on. Do it for about 20 revolutions and you're gold.

Watch the video, figure out where you are at exactly TEN propshaft revolutions. 1.5:1 will be 15 motor revs. 1.36:1 will be 13.6 motor revs...

MC