Mercury F77Z-6268-AB Chain - Timing

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The remainder of the installation is the reverse of the removal steps.

Carefully compress the timing chain tensioner and place a pin (a drill bit or paper clip will work) into the hole to hold it in the compressed position.

Remove the bolt in the center of the jackshaft sprocket, then remove the sprocket with the jackshaft chain.

Carefully rotate the crankshaft by hand through at least two full revolutions. If any resistance is felt, STOP! There is something wrong, most likely valves contacting the pistons. Find the problem before proceeding. Check work and see if any updated repair information is available.

Install the timing chain stationary guides and tighten the bolts to the specified torque.

Remove the two tensioner mounting bolts and then the tensioner itself.

Slowly turn the crankshaft counterclockwise until the slightest movement is seen on the dial indicator. Check to see how far the damper TDC timing mark has moved away from the pointer.

The tensioner is installed to the correct depth when a snap is heard. The tensioner shoe can then be installed, and the plastic clip can be removed with pliers.

Pry the camshaft forward with a large screwdriver or prybar between the camshaft sprocket and the block, then note the dial indicator reading and compare with the endplay.

1. Remove the timing chain cover. 2. Remove the rocker arm shafts. 3. Push the camshaft to the rear as far as it will go. 4. Install a dial indicator with its pointer on the camshaft sprocket bolt and set the indicator to zero. 5. Pry the camshaft forward with a large screwdriver or prybar between the camshaft sprocket and the block. Note the dial indicator reading and compare it with the endplay. Replace the camshaft thrust plate if endplay is excessive.

Mark a reference point on the block approximately halfway along the chain and measure from that point to the right side of the chain.

Remove the bolts retaining the jack shaft chain tensioner and the jack shaft chain guide.

Install the camshaft bolt and washer and tighten the bolts to the specified torque.

Make sure the number one piston is at the top of its stroke (TDC). The crankshaft keyway should point straight up.

Inspect the crankshaft gear for damage or wear, such as grooved or worn teeth that can cause poor meshing of the gear and the chain, leading to chain failure.

Use a gasket scraper to remove all traces of old gasket material and sealant from the cover and engine block. Wipe the cover and block sealing surfaces with a cloth saturated with lacquer thinner or acetone.

Install a dial indicator with its pointer on the camshaft sprocket bolt and set the indicator to zero.