Mercruiser 120 no spark

[Sniper18leafs]

Hey everyone new to this boating thing and got myself a project boat it's a 1984 thundercraft, has a 2.5l mercruiser 120, Engine cranks over good but no spark. Going to be changing the points just wondering what else will cause no spark on those engines or if anyone has a wiring diagram so I can make sure everything is correct.

 

[achris]

Hello Sniper18leafs . To get the right engine wiring diagram, we need to know a few things.

1. An engine serial number.
2. If the instrument panel has an ammeter or a volt meter.
3. The colour of the wires on the + of the coil.
4. If it has a fuse on the starter motor terminal.

Chris..........

 

[Bondo]

Going to be changing the points just wondering what else will cause no spark on those engines or

Ayuh,....... Welcome Aboard,....... If there's power at the coil's (+) tiny terminal, My guess is the points will fix it,.....

 

[Sniper18leafs]

Serial number is 6769888
has a volt meter
Wire coming off the + is solid bsolid but doesnt look original
Start motor has a red box looks almost like a relay

I tested the + terminal on the coil and its showing 11.5

 

[79Invader]

What color is the wire on the + side of coil? Pop the cap off and inspect points for corrosion or pitting. Heck might as well give them a light sand while you're in there; or just convert to electronic ignition, there is kits online all over.

Bondo is right, if the coil has power like you said, points is likely at fault.

 

[achris]

Serial number is 6769888
has a volt meter
Wire coming off the + is solid bsolid but doesnt look original
Start motor has a red box looks almost like a relay

I tested the + terminal on the coil and its showing 11.5

1984 model. It's a '120R', so this is your wiring diagrams... (I'm going to assume it's a Mando alternator, because Merc used those the most at that point in time. If it's a Delco, let me know...)

Engine

Instrument cluster


Trim pump (Assuming Dual solenoid system)



Let me know if any of these aren't right, and if you need anything else.

Chris.......