knocking sound from lower unit that came then disappeared?

[dave buckner]

i have '74 mercruiser 165hp i/o i have had for one month. boat seems to be well cared for and it has performed flawlessly until today. all at once a knocking sound appeared from the lower unit(motor sonds fine). as rpms increase, knocking increased.(propeller shows no signs of contact with ground) i was worried something was going to snap, so i nursed boat home at idle. when i got close to ramp it seemed sound was gone , i increased rpms and boat planed out, etc with no noise. problem seemed to disappear. whats going on?? does this sound like gimbal bearing? i intend to recheck lower unit oil tomorrow, but it was at proper level with no water in it when i bought boat. any input would be appreciated. THANKS, DAVE

 

[daveswaves]

Re: knocking sound from lower unit that came then disappeared?

Sounds like you found my fishing rod,can I have it back?? Seriously, you may have snagged something that is now gone. The other possibility is the shift cable adjustment allowing the drive to come in and out of gear. If that is ok it could be the universal joint's in the drive that hung up and then released. Check adjustments first before you pull drive to grease/check u joints. Others may have other ideas too.