1970 merc 20hp tunderbolt ign prob

[Eshaw150]

To start with this motor is what we believe a 1970 model it is a 200 seres and has the thunderbolt ign system. to start with i got it and it was over heating i replaced the water pump and housing. It died on the water and we had to use the troling motor to get back to the dock. I got it home and took the carb abart and cleaned everthing. It was extremly nasty. then it would run and die only run for about 15 seconds. Today i went back out to tinker with it somemore and It does not have any fire to the plugs. also while running it we heard a loud pop and the engine stoped and had no compresson. i checked the flywheel key and it is good. Now it turns over and has good compression but dosent have any fire.

I am not familler with this older motors my other motor is fuelinjected

 

[Eshaw150]

Re: 1970 merc 20hp tunderbolt ign prob

Any help is apprecitated

 

[jbjennings]

Re: 1970 merc 20hp tunderbolt ign prob

I don't understand how it could have NO compression, and then suddenly have GOOD compression? How did you check compression, what was/is the compressioin on both cylinders, and if it didn't have compression at all at one time and now it does, what did you do to fix the compression problem?

Next, as far as spark, does either plug wire have any spark? I'm not sure if it has points and coils or not, I can't remember. If it has points, clean them and regap. I'm not a good enough mercury tinkerer to tell you how to check the trigger, switchbox, and such if it has those. At least you'll have a bump to top....:redface:
Good luck,
JBJ

 

[jbjennings]

Re: 1970 merc 20hp tunderbolt ign prob

One more thing---disconnect the kill switch and check for spark. Those old kill buttons are notorious for giving trouble.
Just a thought,
JBJ

 

[Eshaw150]

Re: 1970 merc 20hp tunderbolt ign prob

what i mean my no comperssion is that the pistons were not moving as the rope was turned
and neither wire was getting spark ill check the kill botton this weekend and let yall know that was my thought and it has coils

 

[83eska]

Re: 1970 merc 20hp tunderbolt ign prob

if its a 70 or 71 model the stator has the switch box built into it and has points also, just bought a new stator for mine, CDI part # 174-3996

 

[Eshaw150]

Re: 1970 merc 20hp tunderbolt ign prob

IM not sure the year of it excatly it has a coil on it that has the plug wires i cant really tell what excatly year it is but i know its in the 70s