A mechanic suggested conducting a cylinder drop test on my 1994 Mercury 3.0L Offshore 225-HP 2-stroke carbureted outboard to help diagnose rough running. In the test, spark plugs are disconnected one at a time to see what effect this has on the rpm. A substantial drop means that cylinder is probably firing well, whereas if there is little or limited effect this implies that there is a problem with the cylinder. By conducting this test in conjunction with testing spark plug wires with a timing light, it's possible to differentiate between an electrical vs. fuel-related problem. I'll also be doing a compression test.
I've heard two opinions about how to carry out the cylinder drop test:
1) Leave the engine running throughout. Disconnect each spark plug wire using a well-insulated pair of spark plug pliers.
2) Turn off the engine when disconnecting each wire. Make sure to ground out the disconnected spark plug wire. Then run the engine briefly to observe rpm. Turn off the engine, and repeat with the next spark plug wire.
I gather that the advantage of the first approach is that you get a better sense of subtle changes as each wire is disconnected. The advantages of the second approach are that it's safer, and it also avoids electrical damage to the stator or power pack that might be possible if the spark plug wire were ungrounded.
Any opinion on which approach would be better with my 225-HP 2-stroke V-6? I'm confident I can avoid getting shocked, I just want to make sure I don't damage the electrical components but meanwhile would like to get the most useful results possible.
I've heard two opinions about how to carry out the cylinder drop test:
1) Leave the engine running throughout. Disconnect each spark plug wire using a well-insulated pair of spark plug pliers.
2) Turn off the engine when disconnecting each wire. Make sure to ground out the disconnected spark plug wire. Then run the engine briefly to observe rpm. Turn off the engine, and repeat with the next spark plug wire.
I gather that the advantage of the first approach is that you get a better sense of subtle changes as each wire is disconnected. The advantages of the second approach are that it's safer, and it also avoids electrical damage to the stator or power pack that might be possible if the spark plug wire were ungrounded.
Any opinion on which approach would be better with my 225-HP 2-stroke V-6? I'm confident I can avoid getting shocked, I just want to make sure I don't damage the electrical components but meanwhile would like to get the most useful results possible.