Mercury 7.5 HP and 9.8 HP reed block and crank shaft showing signs of wear

Been a slow week, waiting for parts to come in the mail.

To replace the bearings I had to split the crank case which gave me access to the reed block. You can see the reed block here:

IMG_2102The reed block splits the crank case in two and the carburetor actually flows through this reed block. in the picture above you can see the carb on the right.



Here is the reed block in the crank case, the reed block splits in two. The crank shaft doesn’t actually ride of the reed block as it is made of aluminum, but the fit is fairly close.



What are the groves ? Those are called labyrinth seals, they are used to prevent leaks between the crankshaft and the reed block. If you look closely the grooves are almost ground flat on one side of the reed block, this is from loose crank bearings. Unfortunately I wont be replacing this reed block with a new one so this reed block will be leaking slightly more them normal.


Closer inspection of the grooves shows that they have been hammered flat. The right side of the grooves must been opposite of the load force.

wornreedHere is the aluminum build up from the reed block on the crank shaft.