79 Merc 700

[TomLund]

Hi and good morning say i need some help.

Last fall as i was winterizing my four winns i was cranking over the 70 horse it was turning over wouldn't fire all at once there was a spark at the battery and then nothing. What i can't figure out if it could be a fuse or if something else. Also took the plugs out 1 and 3 looked used but 2 looks like it has not been running. I know the carbs need a good cleaning and i pick up a fuel pump rebuild kit.


Ideas...........

Thanks again

Tom

[Retro Performance]

IF THE SPARK WAS AT THE BATTERY I WOULD THINK IT HAS TO BE BAD/DIRTY/LOOSE CABLE CONNECTIONS.........I DO NOT KNOW HOW ANYTHING ON THE POWERHEAD COULD CAUSE A SPARK THERE.  MY MEMORY IS THAT 1979 HAD EITHER NO FUSE OR AN AGC20 AMP(GLASS) FUSE THAT I THINK WOULD BE IN A HOLDER ON THE RIGHT? SIDE OF THE POWERHEAD.  TOM I CAME ACROSS A COMPLETE 3.0 ENGINE HARNESS WITH A COIL IN IT, I WILL POST A PHOTO TONIGHT TO SEE IF IT WILL DO YOU ANY GOOD.

[TomLund]

Sounds good thanks Don. The motor is a 79 i am guess that it could be a loose connection but i will check to see if there is a fuse. another question is it hard to take apart and clean the carbs?

[Rich_V174SS]

If I understand correctly you were cranking the engine, there was a spark at the battery and then no sign of life? Sounds to me like a loose battery cable. Make sure they're clean, shiny, and tight.

[Retro Performance]

I found this harness when I was housecleaning......it is the engine harness for 3.0, if you think you can use it you are welcome to it. I will be bringing a couple things up to Rosscoe in the not distant future. I think that would put me close to Stillwater on the ride out.  Let me know.  I think I would check spark once you get the 70 cranking, sounds like maybe the clean one is not firing...........

[TomLund]

If you are you looking to get rid of it then i will take it off your hands let me know when you will be out this way would be good to see you again thanks

Tom

[Hyperacme]

Tom
There a merc repair manual here  ...
http://forum.cgoamn.com/index.php?topic=2927.0

For a newer 3cyl. Merc but most info should be the same ..

[TomLund]

Hey whats the best way to check a coil if its just you and no one else? And you don't have a spark testing tool. I was thinking of laying the plug on the block and crancking the motor but i am not sure my arms are that long hehehe


Tom

[Retro Performance]

      Tom, I think this would be one way,     If you can get the engine started on a hose(running on 2 cylinders) and you have a timing light clip it on each wire while running. If we assume no spark on number two cylinder, stop the engine, switch number 1 and number 2 coils.....if the problem remains on number 2 you have a problem with primary voltage supply to coil number 2........if the problem (no spark) migrates to cylinder number 1 the coil is bad (what was previously number 2 coil).  Is the cranking problem solved?

[TomLund]

Yes she crankes nice and strong Retro what is a good compression for for 700 i can't find any numbers


Thank

[TomLund]

update I hook a timing light to each spark plug wire pulled the trigger and turned the key and the timing light flashed not knowing a whole lot about outboards i assume there is spark to all three plugs. Now i quess the carbs need a good cleaning. the more and more i think about it this guy that i got the boat from did not know anything lol


Tom

[Rich_V174SS]

If you've got spark that leaves 2 more items you need to check for to make it run - fuel & compression. Compression readings should be over 100 per cylinder, anything less and it won't run. Excellent compression is over 120 per cylinder. Fuel - outboards need to be "wet" to start and throttle/timing needs to be advanced, and the choke must be held while cranking until it fires. If you're not getting fuel then the carbs will need cleaning out.

[TomLund]

Thanks Rich i did find that the coil on number 2 is not sparking oh yes but it will lol

[TomLund]

Its all good put in coil checked for spark put it on the muffs a boom off to the races. Also got a a call some one wants to come out a take a look at it hopfully it will go on the back of there ride. That money will be used for the 66 my fingers are crossed.


Thanks for all the help

Tom

[Hyperacme]

Hope she sells Tom !

[TomLund]

me too