This leads me to ask another dumb question. I bought a timing light, hooked the inductor onto the #1 spark plug wire. When I looked at the timing pointer with the timing light on the crank pulley the only mark I could see was on the outer lip of the pulley. Is that where the mark should be? I've never adjusted timing so I'm not 100% sure what I'm looking at.
I did the service bulletin that change the gas ...
Technical Bulletin
1/06
Revised Initial Ignition Timing For
MerCruiser 3.7L Engines
The AERA Technical Committee offers the following information regarding revised initial
ignition timing for MerCruiser 3.7L engines. This revision is to help prevent engine dam-
age due to the unknown quality of gasoline being used today.
Since the decline of gasoline quality over the past number of years, it has been recommend-
ed by Mercury Marine to set the initial timing at 4° BTDC. This is in place of the original
factory setting of 8° BTDC, which is also published in the older factory service manuals.
Doing so will make the engine more tolerant of today’s unknown quality gasoline, with an
unnoticeable change in engine performance.
Engines were originally set at 8° BTDC and piston failures in the #1 and #4 cylinders were
common. The root cause of those failures is the unknown quality of gasoline for the amount
of ignition timing and compression being used. The poorer the quality of gasoline, the more
likely a piston will burn. Poor fuel burns differently, and in these cases, it has caused pis-
ton failures that appear like over-advanced ignition timing. Due to the quality of gasoline
declining over time, and the resulting engine failures, the initial timing should be set to 4°
BTDC for these engines.
MerCruiser refers to the 3.7L engine as 3.7 LX, MIE 470, MCM 470, 485, 488, 165, 170, 180
and 190. The timing information has been updated in current MerCruiser factory service
manuals published after 1987.
