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1985 Mercury 90 HP (Inline 6 CYL) Knocking Hard Help Please (Video included)

D

Dboy95

New member
Hey guys I’m back from a while ago after replacing my stator and has been running beautifully since. Unfortunately today it started to knock. It’s knocking hard at idle and in gear too. It still runs but I headed for home as soon as I could. Sounds like it is coming from the mid/lower part of the motor.

https://vimeo.com/452883717
 
Make sure flywheel nut is tight.----Check gear oil.-----Remove bypass covers and have a look at pistons and rings.----Hopefully it was not running with an autoblend oiling system.---You did install a new water pump impeller recently I hope.
 
racerone said:
Make sure flywheel nut is tight.----Check gear oil.-----Remove bypass covers and have a look at pistons and rings.----Hopefully it was not running with an autoblend oiling system.---You did install a new water pump impeller recently I hope.
Click to expand...
Hey Race, it will be a couple weeks before I’m back at the lake but I want to compile a list of possible issues as soon as possible and I’ll start here. Firstly where do I find the gear oil? Will have to look at pistons and rings when I’m there next. I mix my own fuel 50:1 so I don’t think it’s an auto blend system. And as far the water pump impeller goes I have not checked it either.

It is pretty distinct knock so if someone could point me in a definite direction that would be amazing. If not any input is appreciated. Maybe someone has had this issue and fixed it in the past let me know or point me to any other threads that could help. Thank you all in advance.
 
It could be Flywheel at very least, is there a reason it would come loose? Maybe loose from when stator went in. Is there a torque spec for these bolts?
 
Most folks would just remove the nut to remove the flywheel.----Sounds like you removed the 8 screws.-----But check the flexplate on the flywheel for cracks.
 
I will open her up in a couple weeks boys then get back to you!

I have to add that this is an a amazing motor and I appreciate you guy, cheers!
 
There MUST be a flat washer under that crankshaft nut---and it has to be the right one. If not, you'll hear that knocking.

Jeff
 
If you don't see anything obvious up top go to a parts house and buy an inexpensive mechanics stethoscope and you may be able to figure out what area the noise is coming from which will help the diagnosis. If you have to do that I would have the engine in the water so as to quieten the exhaust noise as much as possible so you can listen.
 
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