Compression Test and Spark Test Questions?

[achilles555]

I'm wanting to do a compression test and check the spark on my 1987 Mercury Classic 50 [45 HP}, and I have a couple of questions. Can I do these tests with the fuel line unhooked? I just replaced the impeller. Could it damage the impeller to turn the motor over several times with no water...without the ears? Could I damage the cylinder walls without the gas/oil mixture running through it?

Lastly, do you guys have any good step by step links/forum posts for checking compression and spark? I ordered the manual, but I,m anxious to get started. Any help is much appreciated. AC.

 

[13lokei]

Re: Compression Test and Spark Test Questions?

The oil clinging to your cylinder walls from your last run will lube enough for a compression test. The water pump wont be hurt from the slow cranking rpms while checking compression.