Mercruiser 120 starting stumped?

mrzooom

Petty Officer 3rd Class
Joined
Mar 31, 2023
Messages
80
Ok, this old mid 80's 120 came to me non running. Installed starter, got crank. No fuel to carb from pump so I I installed brand new carter mech fuel pump had laying around. Fuel restored to old crusty 2bl carb. Disassembled carb, cleaned it, reassembled and installed on manifold.
Charged battery, 12v to + coil. Strong spark at plugs. No fire? Purple wire at coil +.
Kind of brown and tan (2 other wires) at coil+. Dizzy black to coil-. Tan tach wire at coil-. Boom, no fire??? Ok, took all connections off dizzy except dizzy wire. Jumped from battery to coil+... Not only did it fire but almost knock me out of boat... Anyway without throttle linkage I had no way to much. It reved up like a rocket while just grabbed high tension lead off coil and disconnected the battery -..

In addition to some forien metal sound bouncing around, it was spitting out milk shake into bilge, etc.
What happened? Any suggestions? I have no idea...
Scott
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
49,560
I would check for a crack under the manifold. That will cause it to milkshake.

Pressure test the cooling system

Check for rusted thru head
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
42,058
In addition to some forien metal sound bouncing around, it was spitting out milk shake into bilge, etc. What happened? Any suggestions? I have no idea...
Scott
For oil and water going into the bilge I would say busted block
 

kenny nunez

Captain
Joined
Jun 20, 2017
Messages
3,290
If there is no hole on top of the head then you will find it at the base of the water jacket inside the crankcase. That area is the thinnest part of those engines.
 

Black58

Seaman Apprentice
Joined
Mar 9, 2024
Messages
39
Jumped from battery to coil+... Not only did it fire but almost knock me out of boat...
Best laugh all day. Geezus!
 
Top