Need help diagnosing internal knocking on on my 2000 150 hp johnson

carneyw

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Oct 18, 2014
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[FONT=Verdana, Helvetica, sans-serif]Our 150 Johnson has developed an internal knocking noise. It can be heard faintly at idle. It can be heard well if you put your ear on top of the flywheel cover and you can feel it when touching the fly wheel cover. If you rev it up a bit in neutral it is much more noticeable and sounds horrible. When under power it goes away when under load, when accelerating from a stop but comes back once on plane. I would definitely guess it is something in the lower end. I had an outboard guy (recommended by my marina) look at it and he tells me its ok and running it like it is will be fine and won't cause any more damage. I am not very confident in his diagnosis and would like a second opinion for peace of mind.[/FONT]
 
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Bosunsmate

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Apr 7, 2012
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Do a compression test
How much play in the flywheel? in what directions, front and back, side t side, up and down.
Move each piston to top dead centre and then put a screwdriver with some cloth on it through the sparkplug holes and see how much movement you get from the pistons, is it even between cylinders?
That checks bearings
 

carneyw

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Oct 18, 2014
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Compression test showed ranged from 100-110. Mechanic found was some water in the cylinders and replaced all the head orings. He said all pistons and cylinder walls looked good and clean.
 

carneyw

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Oct 18, 2014
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Boobie, It's a 2 stroke. What would the gear case lube have to do with a knocking noise in the power head?
 

boobie

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If you have a problem in the lower unit, sound can travel up the drive shaft and you think you have a power head prob but don't. A friend of mine once tore a power head completely apart because of a knock and didn't find anything. Turned out to be the upper drive shaft bearing in the lower unit. Sound travels!!
 

Bosunsmate

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If the engines being unused for a day or so look at the plug any rust means you still have water getting in which can cause bad sounds
 

Bosunsmate

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Also water in the powerhead causes problems quickly, rusting of bearings and then a knock so check those piston movements at tdc if you can
 

Faztbullet

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First dont listen the that mechanic as its already hurt!!! Check the gearcase oil for metal as Boobie stated a bad gearcase can make you think its in the motor. Also if water has been found in cylinders especially #1 or #5 it has devloped a glue line leak and leaks water into them. Glue line leaks are repairable but $$$ to fix and usually what happens is the water washes skirt of piston of lube and it scuffs and causes knock do to excessive clearance and sometime I have seen the skirt break which usually is ejected out exhaust port. If it was at my shop i would check lower first and then check plugs for moisture 2nd.
 
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