Out drive ID

[Jboating]

Would like to know if there’s a way to tell what gearing I have in this out drive besides counting teeth. I’m guessing it’s an alpha1 but it’s not marked and the only numbers stamped on the side I believe reads cc303142. The first letter might be an O (Oscar) although it’s difficult to read. If there’s any websites where somone can drop a link that would be great! P.S. I know there are forums out their but I’m on the road and difficult to navigate on my phone. Thanks!

 

[jrs_diesel]

Drive ratios were usually determined by what engine was attached to it. Generally, lower power engines had lower gears.

What engine do you have?

 

[Jboating]

Well I’m running a 260 Merc. Problem is I bought the boat from a friend who put the wrong outdrive in because of who knows?!? I was told it was the wrong gearing for the motor and runs the RPMs to high at WOT and would blow my motor up. He has since forgot what drive I have on now and what is the correct one I need. Some more info if this helps- ‘85 Sunrunner 21.5’ with the 260 Merc.

 

[achris]

According to the serial number, 0C303142, that was a 1.84:1 when it left the factory (1988). What has happened to it between then and now is anybody's guess.

The only way to find the ratio if you don't want to open it up is to remove the plugs from the engine, and having a friend count the propeller revolutions, put it in forward gear, and turn the engine until the prop has turned 10 times. Divided the number of times the engine turned to get 10 prop turns and you have the ratio.

As for the 'correct' ratio to run with a 260... There is no 'correct' ratio. Generally, 260s were supplied with a 1.5:1 drive, but if you were to drop that engine in a bigger/heavier boat or use it at high altitude, you would consider a change to a higher reduction...

Chris..........

 

[Jboating]

So let’s hypothetically say that’s the gears in this drive is factory. Is that to high or to low of a gearing for a 260? Is there a recommended outdrive for a 260 Merc for the size boat (if the size of the boat matters).

 

[Bt Doctur]

for a 260 Hp motor `1.50 is correct using a normal type of boat 23-26 foot boat, etc

 

[achris]

In an average 21'6 boat, I would think 1.84 would be too much reduction. You'd have to look at a VERY high pitch prop, right at the top end of the ones normally manufactured. Something in the order of 25"... They are around, but if that prop is still too small.... Changing the ratio to 1.5 would bring the prop down to a more common size, 19" or 21"....

And yes, size does matter. It's about the weight the engine has to push through the water. More weight, less pitch on the prop to allow the engine to reach the recommended WOT rpm. For the 260, you need to be between 4200-4600rpm at wide open... Less than that is overloading the engine, at all revs.... More isn't so bad, but don't run above 4600 for any sustained time.

Chris......

 

[Jboating]

The prop is a solas me0811 15.8x21

 

[achris]

The prop is a solas me0811 15.8x21

WAY too small on that drive on that boat. If you let it, I suspect the engine would pull over 6,000rpm... BTW, Solas don't have a great wrap for efficiency.

 

[Rick Stephens]

Here's a chart for that era Mercruisers that also gives tooth count on the upper gears. You can see and count those if you remove the top cap from the drive. This also gives you general drive ratio ranges for motors during the listed years.

 

[Jboating]

I didn’t buy the prop, this is the set up it had and I’m trying to make it right! When she’s on plane I was clocked at only like 30mph and was running between 3800-4000rpm. I never dared to pin the throttle. I’m wanting to correct this because she should be a faster boat then that lol!

 

[achris]

I'd look at trying to find a 25" 'Black Max' prop and see how that goes. (That's about the biggest you'll find in 'standard' props)... If that's still too big, you are going to need to change the ratio, either get a new gear set fitted in the top box (too expensive to buy the tools and do it yourself), or buy a new 1.5 top box (they're surprisingly cheap!) Or find a good second hand one....

Chris......

 

[Jboating]

I’d like to get a reman/new out drive. I’m not looking to change prop pitch to fix an already wrong problem. The guy who put this drive in never WOT or wanted to go fast to begin with, this was his quick fix to finish out a season on a budget. I’m not saying money’s an issue, but I have money to make it right..

 

[Jboating]

Sorry I have no clue why that attachment showed up lol! Can’t figure out how to delete it?!

 

[Rick Stephens]

I would think you will have no problem selling a working, but wrong ratio drive. CL or eBay, no problemo. Help pay for the right drive.

 

[Jboating]

Anyone in Michigan that knows a reputable company for a reman outdrive? I’ve heard of “All American Outdrive”.

 

[achris]

Sorry I have no clue why that attachment showed up lol! Can’t figure out how to delete it?!

Fixed.

Anyone in Michigan that knows a reputable company for a reman outdrive? I’ve heard of “All American Outdrive”.

Why not try one from us, iboats....

http://www.boatmotors.com/motorparts/index.cgi?pid=7535&flag=2

Chris.............

 

[Jboating]

Like to shop local.

 

[Rick Stephens]

Like to shop local.

Should go to a local forum then. Not one that sells excellent products and provides a nice forum for its customers.