Mercruiser 5.7 Timing (Won't Run)

[Mironaby]

I have a 1994 Bayliner with a 5.7 Merc. Serial # OF131359 left hand rotation. I bought the boat after the previous owner put new heads and was not able to get the boat to run again. I checked the timing and everything appears to be right. I have fuel, spark, and compression. Not much compression as the number 1 pistol has only 80 PSI. I adjusted the valves but it did not improve PSI. The previous owner took the boat to three mechanics and none was able to get it going.

The way I checked the timing was by making sure the piston one was in a compression stroke and that the rotor was pointing towards the number one wire. However, I can not get it to run. I took the front cover off and noticed that when the marks are aligned, the distributor is pointing towards one but the piston is not on the compression stroke.

Do all the marks have to be in place for the engine to be in correct timing? By all the marks I mean the marks aligned in the front chain, the rotor pointing to number 1 and the piston one in compression stroke?

What am I doing wrong?

Thank you.

 

[Don S]

Re: Mercruiser 5.7 Timing (Won't Run)

Sounds to me like you are 180 out. The piston may be up on top, but it may not be on the compression stroke (Both valves on #1 closed)
So, try this. Remove all the spark plugs so you can turn the engine by hand easily. Put your compression tester into #1 spark plug hole (Port head forward cylinder just in case you are a Ford guy)
Now, turn the engine by hand untill you just feel pressure starting to come out of the hose. Continue turning till the timing marks line up. You are now at #1 TDC on the compression stroke. Remove the hose and make sure the piston is on top. A small wood dowl rod works great. Turn the engine slightly to make sure you are feeling the piston.
If it's not at the top of the stroke, either the timing chain and gears are off, or the vibration dampner has spun thus throwing the timing mark off.