81 Mercruiser 165 6 cyl

[clb077]

I have an 81 Mercruiser 165 6 cyl. When I turn the key to start it starts but when I let the key to run it shuts off. I replaced the ignition switch and it does the same thing. I also replaced the ignition coil, points, condensor, fuel pump. It is getting fuel, the spark plugs are firing. I can not figure it out. Please help

 

[cr2k]

Re: 81 Mercruiser 165 6 cyl

You have a bad circut in the IGNITION circut. With the key ON do you get any voltage at the + side of the coil? Could be the resistance wire if you have one (would be a dark brown wire from the + side of the coil). Follow that back until you have power and splice in a new one. Don't run without the resistance wire (if so equipped) it will burn up your coil and leave you stranded.

 

[clb077]

Re: 81 Mercruiser 165 6 cyl

So to do this, I need a voltage meter? As you can tell I do not know much about electrical.

 

[Bondo]

Re: 81 Mercruiser 165 6 cyl

So to do this, I need a voltage meter? As you can tell I do not know much about electrical.

Ayuh,.... Welcome Aboard,... A simple Test Light will work for what ya need to do,...

 

[clb077]

Re: 81 Mercruiser 165 6 cyl

Right on. Thanks guys.

 

[clb077]

Re: 81 Mercruiser 165 6 cyl

Is there a ignition sensor on this motor?

 

[achris]

Re: 81 Mercruiser 165 6 cyl

Is there a ignition sensor on this motor?

What on earth is an 'ignition sensor'????... If you mean 'knock sensor', then no...

Sounds very much like you need a 'resistance wire' kit. All the instruction for fitting it are in the kit. OEM part number is 84-94227A2

Chris.....

 

[Maclin]

Re: 81 Mercruiser 165 6 cyl

clb,

This may help you understand why it could start and run with key in the START position but die immediately when the key returns to ON after starting...

Power to the coil is limited by a ballast resistor when the igniton is ON. This ballast is needed for differing reasons, but IS needed for most ignition coils and your engine has this type of ignition. So, with just the key in ON there will be about 9 volts to the coil, this is absolutely normal and as designed. If there is no voltage in this condition then there could be a problem with the ballast resistance component or wiring/connections.

When the key is in the START/CRANK position this ballast is bypassed to give some extra spark just during cranking.

So if there is a problem with the ballast resistance component or the wiring in that circuit then the coil can only fire when the key is in the START/CRANK. Engine starts , key goes back to ON and the coil loses power, engine dies .

 

[clb077]

Re: 81 Mercruiser 165 6 cyl

Ok so I bought a continuity tester and checked the positive side of the ignition coil and it lit up. Does this mean it is getting 12 volts?

 

[Don S]

Re: 81 Mercruiser 165 6 cyl

Did you buy a continuity tester or a 12volt test light? Big difference.

 

[clb077]

Re: 81 Mercruiser 165 6 cyl

I bought a continuity tester.Where canI buy a test light at? Auto parts store?

 

[clb077]

Re: 81 Mercruiser 165 6 cyl

Sorry guys, I am new to this. Lol

 

[Don S]

Re: 81 Mercruiser 165 6 cyl

Any hardware store, walmart, autoparts store, etc.

They have a 12 V bulb in them and a ground wire and the light lights up when you have power turned on and the ground wire is hooked to ground.
A continuity tester has a battery in it and powers a wire to see if there is continuity (no breaks in the wire)

 

[Don S]

Re: 81 Mercruiser 165 6 cyl

Any hardware store, walmart, autoparts store, etc.

They have a 12 V bulb in them and a ground wire and the light lights up when you have power turned on and the ground wire is hooked to ground.
A continuity tester has a battery in it and powers a wire to see if there is continuity (no breaks in the wire)

CLICK HERE

 

[achris]

Re: 81 Mercruiser 165 6 cyl

Sorry guys, I am new to this. Lol

Electrics, engines or forums?

 

[clb077]

Re: 81 Mercruiser 165 6 cyl

Electrics Achris

 

[clb077]

Re: 81 Mercruiser 165 6 cyl

Ok, so I tested the plus side of ignition coil, light did not come on. I tested all 4 termanals on the back off the ignition switch all lit up except the c termanal. Dose this mean that is the bad wire? Thanks for all your help guys.

 

[Don S]

Re: 81 Mercruiser 165 6 cyl

If your test light is hooked up like the picture below, then either the kill switch is bad, or one of the connections up to the resistor wire or the resistor wire itself is dead. You need to work your way from the ignitions switch toward the engine until you find where the test light stops lighting.

 

[clb077]

Re: 81 Mercruiser 165 6 cyl

If I have a kill switch I have no idea where it is. My boat is a 1981 Glassmate Fish/Ski.

 

[achris]

Re: 81 Mercruiser 165 6 cyl

If your test light is hooked up like the picture below, then either the kill switch is bad, or one of the connections up to the resistor wire or the resistor wire itself is dead. You need to work your way from the ignitions switch toward the engine until you find where the test light stops lighting.

1981... thinking thinking thinking.... Nope, don't think they had ignition kill switches back then.....

Looks like the resistance wire...

Chris...
(now? Can I post it now Don? )