I am considering purchasing a 1991 Rinker Captiva 206 with a 350 mag and Alpha gen 2. After inspecting the boat aside from some small easily repairable gel coat nicks the only problem I found was a bent prop shaft...the owner admitted to hitting "a submerged log" while taking off and swears it was a very low speed hit on initial take off...no cracks in the gel anywhere on the transom. Is this an easy repair? should anything else be checked? I heard no noise from the drive and I litterally had my ear pressed against it.

Bent shaft or twisted splines?????

A bent shaft will cause a pretty good vibration while underway and will take out the bearings eventually. Slightly twisted splines alone won't cause any huge issues, but causes the shaft to weaken slightly and another hit might cause it to twist more and break.

I understand this Griff, I have never changed a prop shaft before and was wondering if this is a huge undertaking requiring a bunch of special Mercruiser tools? I really like the boat but don't want to pay $7500 plus end up taking the lower unit to a marina for repair and end up with an additional $1200 repair. I am a VERY competant auto mechanic with every concevible AUTO tool...but this is not an automobile.

You need a few special tools and need to know how to set it up.
You can buy a complete SEI Alpha lower for $745.
http://www.sterndrive.cc/mm5/merchan...owerSterndrive

I agree with Griff. It does take special tools to work on drives. A prop shaft is probably a $300-400 part but the labor could be that much as well. Worst case is an entire SEI lower replacement as he suggested. Lots of people have used them w/o issue.

Contact "Mr Gadgets" here on OSO. He is a good guy and can
give you an estimate for repair. He is 2 1/2 hours away from
you but is a drive expert. If you can see the "runout" of a bent
shaft it needs to be fixed. Subtract the cost of repair from the
purchase price and have fun. Leaving the lower unit "as-is"
will only delay the needed repair and increase the damage
and the cost to repair. You may get 12 minutes of use out of
the drive or five years. It is a matter of "when not if" it fails.
Attempting the repair without an experienced mechanic
standing next to you would be silly.

Please tell me you are not getting rid of the Cobalt for a
Rinker?

Cobalt is already gone...sold it for a down payment on our house. The wife wanted a pontoon so im getting rid of it for the Rinker. As an auto mechanic I am well aware of the damaging effects of harmonic vibrations which is why I'm asking. I have been building Rear differentials and manual trans for 20 years and don't feel uncomfortable setting turning torque, preload and lash I cant beleive that setting up an outdrive is that much more difficult than a differential or trans...different yes but if the proper steps are followed I feel I am more than competant with the correct tools. I will get ahold of Mr. Gadgets and get an estimate but for some reason Marine mechanics seem to feel that their labor is worth twice that of an auto mechanic!!!

A buddy that builds trannies and rearends now builds our drives.....your correct in that it's "the same" if you know the specs. A group of us bought all the tools and manuals so he does our drives for us now. The upper uses more "special" tools but we spent nearly $2K getting everything to do uppers and lowers....I think the manual is over $100.00????

They can be straightened if not to bad. I had a bent prop shaft for a couple years and didn't have any vibration issues. Figured it out when I kept going through hubs (plastic tips on the bottom of the hub). I ended up replacing it before I sold the boat, got a good used one for $150 and had a local marina swap it out for about $135. Took him about 45 minutes. I did bring him just the lower half of the drive so there was no R&R charges for the boat / drive halves.

+2. Bolt on and boat.