Alpha one gear ratio

How to calcullate the drive gear ratio while it is on the boat, without taking the upper unit apart? The serial number is not readable. Can it be done by turning the engine over manualy, and counting the revolutions?

Re: Alpha one gear ratio

What year dou you have?? On my alpha one its a 1:84right

Re: Alpha one gear ratio

You can do it that way also, Use the timing mark on the damper for a reference.

Re: Alpha one gear ratio

Yes, but how to calculate it? What is the ratio of the lower unit?

Re: Alpha one gear ratio

1.32
1.50
1.65
1.84
1.98
It`s overall gear reduction , all lower are the same. The change is in the upper unit gears

Re: Alpha one gear ratio

you may find this helpfull...

http://www.4shared.com/file/113521134/81eff60b/sterndrive_ratio.html

Re: Alpha one gear ratio

Bt Doctur said:

1.32
1.50
1.65
1.84
1.98
It`s overall gear reduction , all lower are the same. The change is in the upper unit gears

Click to expand...

So those numbers represent overall ratio from u-joints to prop shaft, but not just upper unit?

Re: Alpha one gear ratio

The gears are the same in the lower in every alpha... It's the gears in the upper that determine the ratio.

Re: Alpha one gear ratio

No, gears are not the same in the lower, so there is a ratio, it is the same for all lower units, but there is.

Re: Alpha one gear ratio

Aviator5 said:

No, gears are not the same in the lower, so there is a ratio, it is the same for all lower units, but there is.

Click to expand...

You are over thinking it.....
Remove the coil wire, put it in gear, mark the prop, turn the engine in the normal rotation 1 full turn by using the appropriate socket on the bolt at the center of the crank pulley....
Keep turning 1/4 rotation at a time until the mark on the prop is back to original position........
The percentage of that second revoloution is your ratio....
IE, half a turn .5, 5/8 turn, .62 and so on...
The over all ratio is what is relavent, not the upper or lower.....

Re: Alpha one gear ratio

OK, I have it figured out. Here is the story behind this issue. I own this boat (Wellcraft Monte Carlo with twin 4.3s) for the second summer now, I purchase it knowing that it will be a bit of restoration, although it was usable last summer. But I've noticed that port engine won't reach WOT, 3500 max. I blamed it on a tuneup, but left it as is for the rest of the season. I have a complete tunup done over the winter, compression checked, outdrives rebuilt, carburators rebuilt. Everything was perfect, timing checked and set properly. Took it for the ride in the beginnig of the season, hoping that WOT problem is solved - no, still 3500 rpm. Fuel lines and anti siphon valves were replased, no luck. I swapped carburators, fuel pumps, ignition coils, ignition modules, still the same - starboard fine, port 3500. Props were the same, I've checked them before I put it in the water. Finally it strucked me - how about outdrives, The previous owner said that it was serviced in local marina, but after I did all the repairs on my own and discovered a very poor workmanship I would't recommend that marina to anybody. So last sunday I rised outdrives, marked the propellers and turned the engines one turn erach manually, and sure thing - the port was far ahead of starboard. Who would've thought that outdrives where different

Re: Alpha one gear ratio

Damn man, unmatched drives? That's crazy!