2006 f90 outboard tick/knock, help!

Brock.Ward

Petty Officer 2nd Class
Joined
Jul 1, 2010
Messages
148
Hey Everyone, got a 2006 Yamaha F90, just yesterday starting make a weird knock/tick noise in the lower unit.; When i was driving it it almost sounds like somethign is knocking or tapping against the metal slightly in the lower unit. I stopped using it and took it out of the water and am going to look at it today. I am not 100% familiar with these engines as I have always worked on older boats...Are there any lower end issues that are known for this motor? I have read a few posts on the web saying the lower units tend to have issues but am hoping someone can give me some insight on common problems. What to look for if I drop it and check impeller etc. I usually only have replaced an impeller on outboards and replaced the pistons, never really got into the lower unit seals, bearings etc. Any input is helpful, I will be running it after work today with muffs and using my stethescope to find exactly where it is coming from. Any help or feedback is appreciated! Thank you! BTW it runs fine, starts fine, it did die randomly about a week ago but we came to the conclusion that the battery was shot, once replaced ran fine then the very low and quiet knocking/tapping started which sounds like its coming from the lower unit.
 

mjf55

Chief Petty Officer
Joined
Jun 17, 2014
Messages
462
Brock, I think I would change the lower unit oil. When you pull the lower plug look for metal filings or metal pieces on the magnet ( part of the lower plug ). If you heard knocking, they might be there.
Also check the color of the oil. Make sure it is not looking like a milk shake as that would indicate oil intrusion.

When reinstalling the drain/vent plug, use new gaskget / washers. Do not re use the old ones.
 
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