Mercruiser 120 Non-Start Condition - Wiring?

[foxxinabox]

Before I get blasted, yes, I know this is a points and condenser system. I will be upgrading to electronic ignition soon enough. What I'm wonder at this point are these two, seemingly, ground wires and where they go. The ring connector has clearly been screwed down at some point but I'll be darned if I can figure out where. The way the wires curve it looks like it could have connected to the negative on the coil but that seems strange to me. Was this actually a possibility? I don't see any grounding studs or other possible screws in the vicinity. I'm not sure if wiring harnesses are part of the engine or the boat. In the case that is a boat, our craft is a 1977 Sabre T-1800. Again, I will be switching over to electronic ignition but wires floating around are a concern. Any help from you much more knowledgeable folks is greatly appreciated. I've attached a picture showing what I'm talking about. Thank you all.

 

[Scott Danforth]

Grey wire is tach
No need to go to electronic, just service the points

File the points
Set gap
Verify dwell with a meter
Then set timing

 

[dubs283]

How To: Troubleshoot a Points Ignition System

***Please read through ALL the information before attempting any procedure listed here and before asking ANY questions*** ***This tutorial is designed to explain step by step the proper procudures for troubleshooting a no spark issue for an engine with points ignition. If you are here, this...

forums.iboats.com

 

[Scott06]

The grey tach wire will go to the negative side of the coil. I assume someone removed it because tach was shorting out the ignition. If you have no spark it is one of the first troubleshooting steps.

As mentioned nothing wrong with a properly maintained points system, its as good as an electronic system except for maintenance requirements. Go through the troubleshooting guide.

 

[foxxinabox]

Read the guide twice tonight and will see what I can find tomorrow if the kids and weather let me. Anyone happen to have the service manual for a '77 Mercruiser 120?

 

[matt167]

Read the guide twice tonight and will see what I can find tomorrow if the kids and weather let me. Anyone happen to have the service manual for a '77 Mercruiser 120?

Search eBay for oem manuals. I think there’s 2 you need and they cover up to 1990 if you get the latest books. They are fairly inexpensive. Don’t buy a seloc manual

 

[Bondo]

Read the guide twice tonight and will see what I can find tomorrow if the kids and weather let me. Anyone happen to have the service manual for a '77 Mercruiser 120?

Ayuh,..... You need #1 for the motor, 'n I believe #2 covers the rest,....

 

[Scott Danforth]

if you cant find used. new is here. https://publications.brunswick.com/

 

[foxxinabox]

Manual on order. I tested the coil tonight and no spark from it. When I turned the key to on (not starting), I read 11.5V on the voltmeter, not the 4-9V as per the troubleshooting guide. Does this mean the ballast resistors are shot and the coil needs replaced? Do I need to go ahead and test the wiring harness (if so, is the boat to engine connector back at the engine)? I did find an extra purple wire wrapped up underneath the dash if that means anything.

 

[Scott Danforth]

see post #2

you still have to service the points

 

[Scott Danforth]

take your wife's nail file and stick between the point contacts and sand them. should take 5 or 6 swipes of the file

set the gap on the points to .018" when the wiper is on a lobe on the cam

with a dwell meter, make sure your dwell is between 30 and 34 degrees while cranking

• if the dwell meter is not registering anything, your condenser is bad
• if the dwell meter is registering less than 30-34 degrees, your gap is too big
• if the dwell meter is registering more than 30-34 degrees, your gap is too small

then set timing to 4 degrees BTDC

now put the dizzy cap back on

fire it up and then set RPM to 650