Motor wont crank..

[79Merc175]

Hi all. this weekend I went to take my maiden run on the lake and to my dismay my '79 V175 would not start. The starter engages and fuel is getting to the carbs but it will not "pop off" and run. I took it home and put on the muffs to see if I could get it to run and still no joy. I know that there is no gummed gas or blockage in the carb jets but am not 100% sure that I am getting spark. I guess I need to pick up one of this thingamajigs that you can put on the spark plug then attach the plug wire to ensure I am getting spark unless there's an easier way to do it??

Other than fuel and spark what else should I be looking for here so that I can narrow down where the problem is? Are there sensors or other things that I should be weary of?

Thanks in advance!

 

[Barnacle_Bill]

Re: Motor wont crank..

You really need to check for a strong spark at all the plugs.

 

[79Merc175]

Re: Motor wont crank..

Forgive me here and not trying to be smart but isn't a spark a spark?
What defines a "strong spark"?

 

[bullbat]

Re: Motor wont crank..

nope a spark aint just a spark, if the spark is not strong enough the engine wont run you should a good strong blue arc at least a 1/2 inch or so it should arc , if it doesnt its not gonna run worth a crap, if at all all you can do is get an inline spark tester and check it do that and let us know what you get

 

[JB]

Re: Motor wont crank..

Well, yes. A spark is a spark, but many outboards don't fire unless the spark is in the cylinder when it is supposed to be there.

We go on the rule of thumb that if it can't make a blue spark 7/16" long* out in the air it may not make any spark at all in the cylinder under pressure.

*that is my definition of a "strong" spark.

Good luck.