Lower unit knocks

Joined
Oct 11, 2019
Messages
5
Hello, I'm new here and am glad to be a part of this wonderful forum. Now my issue. I have a 2013 90hp 4 stroke mercury. I replaced the waterpimp impeller. On reassembly when fighting things up I heard a snap. When I restarted it, it ran and pumped fine, but when it put it in gear it made a knocking noise. It goes in and out of gear ok, but seems to jamb slightly while engauging. It has a knock when in gear, forward and reverse(not as bad reverse). When the engine is in neutral the prop turns freely, with no grind or any resistance. Any thoughts would be appreciated. Thanks
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,043
You pulled it together with the bolts ?----Did you turn flywheel to engage driveshaft splines before tightening the bolts ?
 

The Force power

Commander
Joined
Feb 3, 2019
Messages
2,241
I thought so. The housing was about 1/4 out when I tightened the bolts. Was that too far out??

As Raceone asked; Did you turn the flywheel while bolting it up? how much pressure did it take to bolt it up? how loud was the "snap"?
I would drop the LU and check the shift-shaft & bench test it's mechanism
 
Joined
Oct 11, 2019
Messages
5
The snap sounded like breaking a pencil. I was thinking about the reassably and forgot a detail. I had the control in drive when takin apart. During the impeller install, the lower moved into neutral. I didnt put the controller back into neutral when I bolted up. So I'm thinking when I failed to do that the shift shaft snapped something in the lower unit. Thoughts?
 

The Force power

Commander
Joined
Feb 3, 2019
Messages
2,241
Regardless (I think) you'll have to drop the the LU & sync. the set up. (I'm not familiar with your motor, but only with the older Mercs.)

But the important thing is not to have too much tension on the bolts when bolting up & turn the fly-wheel when it's close to "on" this way the Drive-shaft slips into place.

If everything is lined-up properly it should/ could slide on all the way till the LU meets the mid-section, yes gravity works against us that why we use the bolts to do the last inch or two.
 
Joined
Oct 11, 2019
Messages
5
Yup, I'm going to drop the unit again. Thanks for the help! I'll follow up after I see what happened, so others hopefully wont do the same thing!
 
Top