1982 Mercruiser 470 - no start (cranks over)...low voltage at coil?

As a few folks may know, I have a 1982 Mercruiser 470 that I purchased from someone that I'm trying to get to start. It turns over just fine, but won't start, but will give a couple of sputters like it wants to. I've done some diagnostics and thought the electrical side was solid, but decided to look at it again. Now I'm questioning the voltage at the coil. To give some background info:


1. Bought it from a guy that worked at an industrial shop that got it from a friend, who said it ran fine when he pulled it out of his boat. Unfortunately, he loosened the distributor hold down bolt and turned it, throwing off the timing. My big mistake was not insisting that he start it up for me before I bought it.


2. Replaced the spark plug wires with new ones (NGK BR6FS gapped to .035), and replaced the points with the Pertronics upgrade to electronic ignition. I also used the Pertronics Flamethrower 2 coil, so I bypassed the resistance wire from the electric choke and ran the bypass to the positive side of the coil. I then hooked up an automotive inline spark tester (the type that goes in between the boot and the spark plug and lights up). Each of the 4 spark plug wires lit up the light on the spark tester.


3. I also ensure that the dizzy and cap/wires were on correctly in the 1-3-2-2 pattern. I bumped the engine until I was at 0 on #1 cylinder (not on the exhaust stroke), looked at the position of the rotor, and ensured the wires were on appropriately. I then had my son turn it over while I shot the pulley with my timing light, and got the timing to around 4 BTDC.


4. I checked compression on all 4 cylinders with throttle wide open and no spark plugs installed, and got numbers of 110/118/108/105 (#1, #2, #3 #4). This is on a cold engine, naturally.


5. I've poured a little gas down the carb and/or starter fluid, and cranked it over. No start. I swear it sounds like it sputters or shudders from time to time and sounds like it wants to start, but doesn't.


So after all this, I backtracked to the electrical side. My battery is a relatively new marine deep cycle 850CCA, and remains charged to around 13.2 volts. While my son cranked over the engine, I measured voltage at the coil, and it was 4.7-5.2 volts. Is this a little low? I've read other posts where it looks like it should be 7-9 volts? During cranking, I measured battery voltage, and it only dropped to 11.7 volts, and jumped back up to 13 after cranking. I was wondering about the integrity of the purple/yellow wire, so I disconnected it from the solenoid, and ran a new one from the solenoid straight to the positive coil side. Same results (4.7-5.2 volts). I also took out the newer Pertronics Flamethrower II coil, and put back in the original and re-connected the bypass wire. Still got 4.7-5.2 volts. Does this sound right or a little low? I want to ensure my electrical side is working properly before moving on to re-diagnosing the other systems (i.e. fuel delivery). I also wonder if my bypass wire between pins 5-6 on the electrical connector aren't making a good contact.


Thanks!

when cranking you should be getting the 12 volts from the starter solenoid. Key switch has no affect during cranking. and it bypasses the resistance wire

Of course of you do not have the crank wire on the solenoid then the key switch is controlling the voltage.

Typically a point ignition has two wires going to the coil, one from the resistance wire (when key is in the run position)
and from the starter solenoid I terminal, (ignition). the other small terminal is the solenoid coil power when in the crank.

so if you have low voltage, could be from the crank I terminal contact inside the solenoid thus the solenoid is weak.........


run a wire from the batter to a on /off switch and then to the + coil.

Disconnect all other wires on the + coil.

Try this.

if it works the the starter solenoid will need to be replaced or repaired.

Thanks for the reply. One thing I forgot to note is that the engine is sitting out of the boat and on mounts in my garage (which is why I am bypassing pins 5 and 6 on the electrical connector). To start, I'm simply using an automobile remote starter switch to jumper between the red power connector on the left to the red/yellow wire lug on the solenoid (to simulate starting with the key switch). Not sure if this makes a difference.

No difference... Try what I said.

I have a 2 switch rig that bypasses the ignition system...and I have used it with motors
Out of the boat to run and set up before install.

TDC top dead center on the crank pulley could be either compression stroke, or exhaust stroke, it alternates with each crank revolution, because the camshaft, & distributor only turn 1/2 way with each Crank revolution (4Cycle engine). So, if you happen to have it wrong, you need to take out the Dizzy, and crank it over exactly one turn to TDC again, & reset your Dizzy on #1.

Hey Kghost - what I actually did was to take the red/yellow wire off the slave solenoid, and hooked it/jumper it directly to the positive side of the battery. I left everything else connected as normal. At that point, I checked voltage across the coil (the old coil), and it was around 10.5 volts. Definitely better. When cranking, it dropped down to around 6.5-7 volts across the coil. Checking prices on those 470 slave solenoids, look like they are relatively cheap and could save me further aggrevation.

Hey Mike - yeah I was in a rush the first time I bumped the engine to reach 0 TDC and forgot to make sure it was on the compression stroke. I ended up with the cap/wires/ 180 out (it was at 0 on the exhaust). I bumped it over until I hit 0 TDC on compression stroke using the ol finger over #1 spark plug hole method, then noted the rotor position and put the cap/wires on appropriately.