Twin Drive Question ?

[Rev]

I smoked one of my outdrives (198? Cris Craft Scorpion w/Merc 260s and Alpha outdrives) on the 4th of July weekend. When I took it apart this weekend (my first time with outdrives, lots of experience w/ motors) the upper gears are chunked and I had water in the fluid (milky). This boat has been extensivly modified (before I bought it) and I have had alot of fun (I am on my sixth set of engines) trying to see how much horsepower I can get from chevy 350's on 87 octane gas. I have been expecting the outdrives to go as I am putting a little over 300 (maybe 325 or so) horsepower into the alphas that I read are only rated for 300 max. I saw another topic where you said your outdrives can take more than 300 horsepower... but I bet you are starting to wonder what my question is?

I havn't gone out to count the teeth on the upper gear set, but I have seen that some of the old gear ratios are not the same as the new gear ratios. I would think that I cannot have mismatched ratios (even if the difference is small) right? Does that mean I will probably have to by two new drives? I also wonder from reading some of the posts... If you buy a complete drive does it come in two halve that I have to assemble? Is it easier to assemple the upper, then put the lower on next?

I also see alot of folks that don't think its a good idea to just change and upper, as the grenaded parts from the upper probably got all through the lower...

Finally, my shift cables are a little streched (you have to go slightly into forward to release reverse), this has been this way on all 3 mercrusers I have owned. I have never fixed it because I have gotten used to the additional motion and I always understood that the outdrive had to come off to replace the shift cable (I have always been a motorhead, not a tranmissionhead). Is now the time to replace the shift cables?

Sorry I got a little longwinded

REV

[Rev]

I am confused on the gear ration

I counted the teeth on the gears (They are torn up but I rechecked many times) and I have 22 teeth on the drive shaft side and 20 teeth on the outdrive side..... that is 1.1 to 1....

Help

rev

[Technical Support]

The alpha series drives were put behind 330 h.p. 7.4L engines, but they didn't hold up well depending on how the boat was used. They will usually hold up okay if you are nice to it out of the hole.

The drives do ship in halves, and I recommend putting the upper and lower together, then installing it on the boat.

Your unit would be a 1.5 to 1 ratio. Any replacement you buy would be a 1.47 to 1

The way the ratio is determined is by adding up the lower and upper gearsets to give you the total ratio from input shaft to output shaft.
The reason the ratios are slightly different now versus a few years ago is because the lower gears changed from 17-28 teeth to 14-21 teeth.

If you just change the upper you would not need to worry about a different ratio as it would still have the 20-22 tooth count. It would be a good idea to take the lower apart to clean and inspect it.

The drives do need to come off to change the cables. Its not a hard job, but if you haven't done it before you definately want to get the proper service manual.

Tech Support

[Rev]

I gave it a lot of thought this weekend and I am going to go with two new complete outdrives..... I have been waiting for these drives to blow up for the last few engine sets. So what all do I need to replace both outdrives? What should I check on the gymbals to make sure they are OK? Any other things I should check and make sure they are good before I reassemble? Can you recommend a good book that has instructions (and pictures) that will help me with putting on the new drives, and replacing shift cables, water puumps etc (I love service manuals, I own one for all my cars!)
Thanks

rob

[Rev]

Ya still there? or are ya working on my question?

[Technical Support]

As far as what all you need, give our sales department a call and they will walk you through it all.

You should check the gimbal bearing and well as the swivel pin area on the transom assembly. If the boat wanders alot at slow speed it is a good indication that it is sloppy.

For the manual, you should just buy the appropriate manual from a merc dealer. You can also look online, I believe somebody has a pdf version online somewhere.

Tech Support