Mercruiser, 888, V8, ignition?????

PSS-Mag · May 22, 2008

Does anyone have a schematic of 1976 Merc 888 302 v8 ignition wiring?

For some reason I'm not getting power to the coil while cranking.
I have power with key in on position though.
I thought it was the old boats wiring and had ran a wire directly from ignition switch to the coil and used it several years that way.

That boat rotted and then sank last year. I saved the motor drive etc and scrapped the boat. I just put the drive line in a new hull and same issue. So apparently it's the motors wiring issue. I don't know if someone has wired the coil wrong at some point over the years, or if it's a bad wire, or what. Or if it pulls power from the starter solenoid while cranking to the coil or what it might could possibly be.

If I can see a schematic of the pre-ignition ignition system, then maybe I can trouble shoot and fix it right. Otherwise the only thing I know to do is run a direct line from the ignition switch to the coil.

chiefalen · May 22, 2008

Re: Mercruiser, 888, V8, ignition?????

run a wire to the dash with a switch from the battery to the coil.run a second wire to the starter with a momentary push switch to the dash and battery and forget about the old wires.

WizeOne · May 22, 2008

Re: Mercruiser, 888, V8, ignition?????

Sounds like you are missing the 12 volt power wire coming up from the starter solenoid. You should have two wires to the positive coil terminal. One is the resisted lead which is powered by the run position on the ignition switch and the other is a full 12v that is only energized when the starter is activated.

Points etc do not like a constant 12+ volts, hence the resisted/ballasted lead from the ign switch. However full poop is necessary when the starter is using up all the juice while turning over to start the engine.

PSS-Mag · May 22, 2008

Re: Mercruiser, 888, V8, ignition?????

WizeOne said:
Sounds like you are missing the 12 volt power wire coming up from the starter solenoid. You should have two wires to the positive coil terminal. One is the resisted lead which is powered by the run position on the ignition switch and the other is a full 12v that is only energized when the starter is activated.

Points etc do not like a constant 12+ volts, hence the resisted/ballasted lead from the ign switch. However full poop is necessary when the starter is using up all the juice while turning over to start the engine.

After I posted and thought about it for a second, I was wondering if I could pull from the starter side of the solenoid. Would save a lot of wire, and be easier than running a wire all the way to the helm too.

PSS-Mag · May 22, 2008

Re: Mercruiser, 888, V8, ignition?????

chiefalen said:
run a wire to the dash with a switch from the battery to the coil.run a second wire to the starter with a momentary push switch to the dash and battery and forget about the old wires.

I've thought about getting rid of the solenoid all together like that.
I use the same one in my boat, truck, wifes SUV, and both lawn mowers and they are all prone to going out at the most inconvenient times. LOL

Nothing like trying to start the boat with a pair of pliers, with a bad unexpected storm approaching fast and your still several miles from the ramp! LOL

Had it happen just like that before! LOL
Racing back to the ramp and trying to load in high winds, rough waters, and lightning striking all around. Yea thats fun!

MikDee · May 22, 2008

Re: Mercruiser, 888, V8, ignition?????

WizeOne said:
Sounds like you are missing the 12 volt power wire coming up from the starter solenoid. You should have two wires to the positive coil terminal. One is the resisted lead which is powered by the run position on the ignition switch and the other is a full 12v that is only energized when the starter is activated.

Points etc do not like a constant 12+ volts, hence the resisted/ballasted lead from the ign switch. However full poop is necessary when the starter is using up all the juice while turning over to start the engine.

This is exactly how it works, as WiseOne posted!

I was gonna explain the exact same thing.

PSS-Mag · May 22, 2008

Re: Mercruiser, 888, V8, ignition?????

Thats what someone had done.... not mentioning any names, but they are likely typing this post...... LOL

Sometime at some point on the old boat either I or PO had put the starter wire on the ignition side of the coil. Moved it over to input, bumped the key and it fired off and purrs. No extra wires needed.

The PO had put the wire from the key switch to the coil before I bought the boat. I knew it when I bought it because I was with him when we did that.

WizeOne · May 22, 2008

Re: Mercruiser, 888, V8, ignition?????

No auto electrician here but methinks that you may have been lucky that you did not fry something by doing that.

Glad you got it worked out. Tis certainly the wonder of iboats, even sans any pithy posting.

Limited-Time · May 22, 2008

Re: Mercruiser, 888, V8, ignition?????

Just a thought.......................but does the kill switch in that set up, ground or interrupt the start circuit??

MikDee · May 22, 2008

Re: Mercruiser, 888, V8, ignition?????

There should be two small wires coming off the (Neg or -) side of the coil, One going into the distributor, Plus One going to the tachometer.
Both starter wires go on the (Pos. or +) or ignition, side of the coil, One resistor wire (Run) And One full 12volts (start) wire.

A kill switch goes on the wire going to the distributor, if used.

Don S · May 22, 2008

Re: Mercruiser, 888, V8, ignition?????

Wiring Diagram

PSS-Mag · May 22, 2008

Re: Mercruiser, 888, V8, ignition?????

WizeOne said:
No auto electrician here but methinks that you may have been lucky that you did not fry something by doing that.

Glad you got it worked out. Tis certainly the wonder of iboats, even sans any pithy posting.

No doubt!

Man if you seen how many grounds were on hot and hots on grounds when I got that old boat. You'd wonder how it kept from burning to Davy Jones locker anyway. I spent a full season finding them and not 100% confident I had found them all yet in 3 years of use.

Thanks for the thoughts and comments guys it's running now.

Thanks for the diagram Don, I'm printing that off now to keep on hand.

Now if I can just get the trim working I'll be boating again this weekend.
Kids are sooo looking forward to it, we have been with out a boat since ours sank last July. Only got to use it once last year and they weren't happy.
I'm not going to disappoint them.

Don S · May 22, 2008

Re: Mercruiser, 888, V8, ignition?????

You really need to keep an eye on ebay for Service manual #2. Would make all your problems easier to find and fix.
Or you could order one from your local Mercruiser dealer.

PSS-Mag · May 22, 2008

Re: Mercruiser, 888, V8, ignition?????

Yea I keep saying that I need to get one, but one of those things I only time that think of it is the second I need it and by the time I got to town, bought it and back, I can usually search here or other forums and find my answers.

I think the trim is, the pump has went out. I can't get it to turn even running either side straight from the battery.

1976SRV190 · Jul 10, 2008

Re: Mercruiser, 888, V8, ignition?????

I have a 1975 Sea Ray SRV 190 with the 888 with 351 heads. Have any of you who have the 888 changed out the ignition module to an electronic module like an Accell or MSD module?

Yellowboat88 · Jun 23, 2009

Re: Mercruiser, 888, V8, ignition?????

Boy, I am having the same problem. The wiring diagram in this thread will no dought help. However, I am having a hard time figuring the firing order. I knows its counter clockwise. I've seen 1-3-7-2-6-5-4-8 and that is actually printed on an old ditributor cap I have. But then a tune up manual I have says the 73' 302 is 1-5-4-2-6-3-7-8. Which is it? I suppose when I regain a spark, I can try both again and see what runs. Until then, I have voltage to my coil, but no spark coming from my coil/distributor. And the voltage reads only 5 volts once I hook up the coil. 12 volts if not connected.

Haut Medoc · Jun 23, 2009

Re: Mercruiser, 888, V8, ignition?????

Yellowboat88 said:
Boy, I am having the same problem. The wiring diagram in this thread will no dought help. However, I am having a hard time figuring the firing order. I knows its counter clockwise. I've seen 1-3-7-2-6-5-4-8 and that is actually printed on an old ditributor cap I have. But then a tune up manual I have says the 73' 302 is 1-5-4-2-6-3-7-8. Which is it? I suppose when I regain a spark, I can try both again and see what runs. Until then, I have voltage to my coil, but no spark coming from my coil/distributor. And the voltage reads only 5 volts once I hook up the coil. 12 volts if not connected.

1-3-7-2-6-5-4-8....
I would disconnect the tach & see what happens....
& start your own thread.....

Mercruiser, 888, V8, ignition?????

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