470 hard start when cold

I have a 1986 Merc 470 that I

I have a 1986 Merc 470 that I replaced the carb and installed a breakerless ignition. Problem is when on a cold start I can crank the engine for about 3 to 5 seconds and as soon as I let of the key it will pop of and start running. I have experimented with hold they key longer and it won't start until I let off the key. When the engine is warm it starts imediatly. The engine has had a full tune up and runs great otherwise.

I was told by a local mechanic that there is a second positive voltage wire that goes from starter relay to the coil. This wire supplies a full 11 to 12 volts bypassing the resistance wire durring starts. To compensate for the high voltage drop to the coil on cold starts.

I was going to test by jumping a test lead form the positive on the battery to the positive on the coil to see if it starts up on first crank on a cold start.

Any ideas if this is a common issue or a good test?

"Yes, and Yes.

I've f

"Yes, and Yes.

I've found that when switching to breakerless (aftermarket) ignition that they seem to require a higher voltage to start. Make sure the bypass wire is working by checking voltage at the "I" terminal on the starter. Then also check the voltage at the coil while cranking. It should be 10-12v for these aftermarket systems to work. The work best when cranking voltage is closer to 12v.

Using a a jumper wire from the battery to the + side of the coil is a good test to see if that is actually your problem."