[ventureman]

I bought a 1977 Merc 1500 I6 a few months back to replace a 1978 Merc 175 Black Max. Recently, I bought a brand new internal wiring harness Part #
84-850220 A1 so that I can use the existing control(Quicksilver) and would retro fit to the 8 pin external wiring. However, the colors on the wires are different from the one on the 1500, part # 84-69236 A1. The wire colors are:
2 yellow, 1 yellow/black stripe, 1 red with 2 extensions(1 male, 1 female), i purple, 2 red/purple stripe on single female, 1 gray, 1 yellow/orange stripe, 1 blue, 1 black, 1 black/yellow stripe, 1 tan/gray stripe. Need help on hook-up.
Also last week, I bought a 1977 Merc 1150. Was told it ran, but NOT!!! Checked compression today, and cylinder no 3 has zero compression. Spark plugs has aluminum pittings on it. Cylinder 1,2,4,5 has 118-121. Did not test cylinder 6(hard to reach). Motor turn freely, but would not start. Question is can the motor start with just 5 cylinders??? If nothing else, this will be a parts motor for the 1500.
Thanks

[Chris1956]

Venture , Those inline sixes can start on 4 cylinders. Don't ask me how I know....


The old wire colors on the 1500 are red for battery, white for +12 V for ignition, grey for choke solenoid, brown for tach signal, black for ground., yellow for starter solenoid I do not think the rest are used. Now remember, the 175 had ADI ignition where the powerpack is grounded to kill the ignition. The distributor on the 1500 needs +12V to run.

OK on the new wiring harnes, yellow is for stator to rectifier and starter solenoid. purple is tach signal(one pole on rectifier), grey is usually accessory, black/yellow is power pack killer, and shouldn't be used.

Why not disconnect the battery and trace 'em from the control box to the motor harness.

[ventureman]

Today, I tried to start the 115. It fires but would immediately dies. But the way that would done with CRC starting fluid with lubricant from Bass Pro. Did noticed that primer bulb did not stay hard even though bulb and lines are new. Did a compression test again on cylinder 3, and it is still ZERO. Piston did move up and down though.
With 0 compression, what would be the most likely failure???
As for the wiring, I didn't get to it yet, but Mercury/Mariner website have a generic color code, but still confusing. I guess I will have to trace it to the control. I downloaded control diagram from Mastertech. Not in a hurry cause
I always fishes out from my partner's boat..

[Chris1956]

Ventureman, If the number 3 cylinder has zero compression, it is likely due to cylinder, piston and ring damage caused by a too lean fuel/air mixture or overheating. If you plan to fix it, you will need to strip down the block and hone or bore the cylinder and install new rings and perhaps a new piston.

You will also need to determine the original cause, or it will occur again.

[ventureman]

Chris, I bought this motor with the understanding that if the motor doesn't run, it will be a parts motor for the 150. I paid $200.00 for the motor, complete with prop, T&T, and steering helm. I still think it is a good deal considering old parts are hard to come by and $$$. Might take powerhead apart when I have time. Have a feeling cylinder wall is scored since piston
does move up and down. Thanks again.