I have a friend with twin counter rotating Alphas on a fishing boat with 3.0 liter mercs. We dropped both lower units to change the impellers. The stbd drive works fine but the port drive rattled when placed in fwd and reverse and would not go into gear until some throttle was applied. The drive did not rattle before the lower was pulled.

Today we took off the problem lower unit and made sure the drive was in fwd with the shifter in fwd and reinstalled but we still have the same rattling problem in fwd and reverse until you give the motor some throttle. Drive goes into neutral OK.

I did pull the upper case off the gimbal on the problems (port) drive to check the ujoints and grease the drive shaft so that is one thing done differently between the drives. Any ideas are appreciated.

Anyone?

What was the resolution? I have a very similar issue right now. Port too!!

I pulled both lowers to replace the impellers, then realized I couldn't find any really good instructions, so I brought both to a shop to replace the impellers. They told me it would be easier for me to get them back on the boat if I gave them the uppers too and they'd put them all together. I did that. Put both on today.

I tried to verify everything was ok by putting each in neutral and verifying each prop spins - both directions. They did. Put them both in forward and both props were locked when I tried to turn clockwise (both RR). Put both in reverse, the starboard locked, but the port prop could still be turned in both directions!! There is a slight clicking noise which appears to be coming from the lower unit. I won't start it and put in gear because I think it will just damage it. I was hoping to take the boat out tomorrow for the "sea trial" after a bit of work, but the marina I had the impellers replaced at is closed on Sundays!

alpha's..number one culprit is shift cables..adjustment

Thanks phragle - I'll check in the morning. I did lift both outdrives with both in reverse and looked behind at the shift levers. The were both pointing in the same direction and seated properly...

You nailed it. THAT WAS IT! 10 minute fix. Disaster to cruising in 10 minutes.

Thanks!