Bravo gear ratio

[metraman]

Can someone tell me to check the gear ratio in my Bravo if turning to engine one complete revolution will do it?

Thanks

[boldts]

Metra,

If you turn the engine 1 full revolution, you can also follow a blade of the prop and get a good estimate of your gear ratio. If you have the 1.5:1 gear, the prop should turn 1 1/2 turns. If you have a 1.65:1 the prop will turn a bit further.

I don't know all the possible gear ratios, but I'm sure they can be found on-line at a site like the Mercury website.

[rayjay]

Metra,

If you turn the engine 1 full revolution, you can also follow a blade of the prop and get a good estimate of your gear ratio. If you have the 1.5:1 gear, the prop should turn 1 1/2 turns. If you have a 1.65:1 the prop will turn a bit further. ...

Not quite correct as outdrive is reduction gearing. For each turn of the engine prop turns .6667 of a revolution with 1.5:1 and .6060 of a revolution with 1.65:1. Engine has to turn 1.5 or 1.65 revolutions respectively for prop to turn once.

rayjay

[metraman]

So if I start at TDC and go 1 1/2 turns my prop will go one turn if its 1:50 gearing.

Thanks

[scott snider]

look at the port side of the upper gear case on the out drive. there should be a drive number on the merc. lable or if the lable is gone the number should be stamped on the case. go to mercruiser.com go to parts express enter the number, you will than be able to find the part number.the ratio should be the last 3 digits of the number. #######150 the ratio for this part number should be 1.50 good luck

[MOP]

So if I start at TDC and go 1 1/2 turns my prop will go one turn if its 1:50 gearing.

Thanks

You have it right it is gear reduction not over drive, the slower a propeller turns the more officiant it is.

Phil

[Donzigo]

Keep in mind that if the Bravo is an old one, they came out first with 1:32 to 1 and many have been replaced. They were gearede too low for the drive and they failed. So, the drive ration on the side might not be correct.

[boldts]

Sorry Metra. Had the right idea, just the wrong end. Thanks guys! I appreciate the correction and will wait for the more experienced to reply next time.

[Formula Jr]

Alphas had 1.32
Bravo 1s 1.36 and 1.50.
:propeller

[Rootsy]

ok here is an easy and MATHEMATICAL way..

get on the net.. find yourself a photo of a degree wheel and print it out... cut it out, paste it to cardboard and cut a hole in the center... the bigger the diameter of the wheel the better also...

now tape a pointer onto the drive extneding over the wheel...

set the motor on TDC and then zero the wheel and pointer on the propshaft.

put the drive in gear

spin the motor 1 revolution (360 degrees) BY HAND TDC to TDC. then note the angular movement of the degree wheel on the propshaft.

divide the number of degrees of rotation of the propshaft by 360 and take the inverse and then you'll have your gear ratio...

the propshaft spins slower than the engine... therefore it is a gear REDUCTION system.

[ToonaFish]

Graph please?

[Donzigo]

Very good explanation..................in certain parts of the world, they leave the stick on the cardboard in place, and turn the entire boat around, just to be sure. If your boat ends up upsidedown, you have a 1:50 reduction gear...... :D

[MOP]

Damn Jamie you were really awake to get that out so precisely! :yes:

[rayjay]

..................in certain parts of the world, they leave the stick on the cardboard in place, and turn the entire boat around, just to be sure. If your boat ends up upsidedown, you have a 1:50 reduction gear...... :D

Now I am rolling on the floor..... :jestera: rayjay

[metraman]

Thanks for all the Info ought to be able to figure it out.