Mercruiser 3.0 only stays running with key engaged?

[Bszakaly97]

Hello new here so I’ll do my best to explain everything and hopefully I’m in the right place, I have a mercruiser 3.0 in a 99 sea ray 180. Just swapped in a new motor with points... hooked up main harness plug and motor only starts and runs with key engaged. 12v at coil when starter is engaged but with just key on have nothing. When hit wire to + side of coil runs great. Tried replacing ignition simply because I had one round that I knew worked and didn’t change anything. Gauges work along with everything on the dash, also should mentioned I jumped pin 5 &6 on engine harness plug and had constant power to coil.. only used the test light but nothing lights up under the ignition so should I be following purple wire all the way back to main plug? Also already bypassed KS thanks for any help in advanced. Also using a deep cycle battery if that matters... just bought the boat so I also do not know it it worked properly with last motor but the motor in it now I had running and idling fine in last boat with no problems

 

[Bt Doctur]

follow the purple wire. if you have 12 at the ign switch then go to the mail harness plug at the engine. pull it apart to inspect

 

[CaptnKingfisher]

When hit wire to + side of coil runs great.

I think I understand what you're saying, if you run a 12v wire to the ignition coil the engine will run. So I agree with the previous poster. The purple resistance wire is your culprit. You can either hunt down the loose connection or broken purple wire (repair it the right way) or if you're stumped, you can buy a ballast resistor from any autoparts store and hook up power from the selenoid through the resistor to the coil.

 

[isaacs]

Does your boat have a kill switch? My boat behaves like that when the kill switch has accidentally been engaged.

 

[Bszakaly97]

I think I understand what you're saying, if you run a 12v wire to the ignition coil the engine will run. So I agree with the previous poster. The purple resistance wire is your culprit. You can either hunt down the loose connection or broken purple wire (repair it the right way) or if you're stumped, you can buy a ballast resistor from any autoparts store and hook up power from the selenoid through the resistor to the coil.

I’ve gone through the whole harness at this point can’t find anything could be the plug itself... so I can buy that resistor anywhere? Hook it up to a 12v source then directly to the coil possible with a switch hooked up? Thanks again

 

[Bszakaly97]

Does your boat have a kill switch? My boat behaves like that when the kill switch has accidentally been engaged.

Yes have bypassed it for the time being DIDNT seem to change anything

 

[Bszakaly97]

I’ve gone through the whole harness at this point can’t find anything could be the plug itself... so I can buy that resistor anywhere? Hook it up to a 12v source then directly to the coil possible with a switch hooked up? Thanks again

Also is there a certain spec of resistor I need ?

 

[alldodge]

Went from electronic to points ignition, are you using the 1999 harness or the older motor harness

Just get a ballast resistor which would read 1.8 to 5 ohms. This will provide the coil with 9V when running

 

[CaptnKingfisher]

Does your boat have a kill switch? My boat behaves like that when the kill switch has accidentally been engaged.

"Also already bypassed KS thanks"

 

[Bszakaly97]

Went from electronic to points ignition, are you using the 1999 harness or the older motor harness

Just get a ballast resistor which would read 1.8 to 5 ohms. This will provide the coil with 9V when running

I’m using 99 harness in boat... and so I can hook up any 12v to the resistor and a switch then to the + side of coil and I should be fine? Thanks

 

[alldodge]

My guess is wiring is not correct. The 99 harness would have only one wire which would be purple going to the + side of the coil.

Points wiring would have 2 wires on the + side of the coil. Purple/Yellow coming from the starter solenoid and a Purple resistance wire coming from the electric choke

How many and what color wires are on the coil + and - post?

 

[Bszakaly97]

My guess is wiring is not correct. The 99 harness would have only one wire which would be purple going to the + side of the coil.

Points wiring would have 2 wires on the + side of the coil. Purple/Yellow coming from the starter solenoid and a Purple resistance wire coming from the electric choke

How many and what color wires are on the coil + and - post?

So I’m still using original harness for motor so it didn’t change there but using 99 harness in boat.. purple/yellow and purple on + side and yellow and a black wire on the other

 

[alldodge]

using original harness for motor

OK the old one

purple/yellow and purple on + side and yellow and a black wire on the other

Don't know about the yellow. Normal would be black for Dizzy and Gray for Tach

The purple may be the resistance wire and if it is, it may need to be connected to the electric choke. Need to trace that wire to determine where it goes to.

 

[Pruno]

Yes have bypassed it for the time being DIDNT seem to change anything

I cant remember if the switch is N.O. or N.C... not sure how you bypassed the switch, but if it's an N.C. switch and you have a break someplace else in the wire it would behave this way.

I'm no expert, but I would trace kill switch wire.

 

[CaptnKingfisher]

I’m using 99 harness in boat... and so I can hook up any 12v to the resistor and a switch then to the + side of coil and I should be fine? Thanks

Yes, I would get my power from the starter selenoid, make sure you're on the right post, should get 12v without cranking. Starter selenoid to ballast resistor to positive post of coil.

 

[alldodge]

should get 12v without cranking. Starter selenoid to ballast resistor to positive post of coil.

Do not agree.
Just the opposite, left post on solenoid (purple/Yellow, key start) gets power while cranking.
Purple (key ON) wire thru resistor

 

[CaptnKingfisher]

I cant remember if the switch is N.O. or N.C... not sure how you bypassed the switch, but if it's an N.C. switch and you have a break someplace else in the wire it would behave this way.

I'm no expert, but I would trace kill switch wire.

I don't know about N.C. switches but I'm assuming it grounds the ignition coil, right? If it was active, he wouldn't have been able to run the motor by hotwiring 12v to the coil (which he did). Maybe I'm misunderstanding how N.C. Killswitch works. I wrench on an omc I/o so this is unfamiliar territory maybe I'm out of my scope

 

[CaptnKingfisher]

Do not agree.
Just the opposite, left post on solenoid (purple/Yellow, key start) gets power while cranking.
Purple (key ON) wire thru resistor

Ah, I stand corrected this is logical

 

[alldodge]

Guys the kill switch is NC for I/O, 2 cycle OB use NO. Power from the key (purple wire) goes thru the kill switch and then to the motor and coil. When pulled it opens removing power to the coil. Bypassing it just takes it out of the equation for now

 

[Pruno]

Guys the kill switch is NC for I/O, 2 cycle OB use NO. Power from the key (purple wire) goes thru the kill switch and then to the motor and coil. When pulled it opens removing power to the coil. Bypassing it just takes it out of the equation for now

Right, so if the KS is jumpered closed, and there is an open someplace else in the circuit, wouldn't it behave as though the kill switch was tripped? (Able to run in start, but not run on run).
Or if the OP removed the KS from the equation by disconnecting the wires from the switch and leaving the circuit open would also be the same.