1976 Mercruiser 165 Fires But Wont Run Inline 6 GM

[GameOnSalmon]

Hi All,

Ok, here is the scoop...

1976 GM 250 I6 Mercrusier 165

Swapped Engines due to previous owner with cracked block. Got engine Fired Up and it ran for about 20 minutes on the muffs. During the initial firing, I had to keep the key cranked over til it caught and ran, basically grinding on the starter. Turned off engine and let sit over night, Thinking we were golden..then

Rained on top of motor... and Now it fires if you stay on the key but wont run. So far i have done the following...

Changed fuel filter - and checked for blockage at the carb... It is pumping fuel.

Today, i put the key in the run position as suggested in another thread and checked Volts at the + side of the coil grounded to Battery Ground... I have 8 volts not 12... (Thanks Don S for fixing my error there) Also this has the Pertronix Electronic ignition.

What is my next step in Testing...or what do I do... Thank you in advance to everyone who took the time to read this.

Regards,
Robert

 

[Don S]

Re: 1976 Mercruiser 165 Fires But Wont Run Inline 6 GM

You don't check ohms on something when the power is on, you check voltage. Turn the key to run, with your meter on DC Volts, red lead on the coil + terminal, and black lead on a good clean ground (NOT the - terminal of the coil), what is your voltage.

 

[GameOnSalmon]

Re: 1976 Mercruiser 165 Fires But Wont Run Inline 6 GM

You don't check ohms on something when the power is on, you check voltage. Turn the key to run, with your meter on DC Volts, red lead on the coil + terminal, and black lead on a good clean ground (NOT the - terminal of the coil), what is your voltage.

Don,
I have 8 volts with key in the run postion, red on the coil + terminal and ground on the battery Ground. Thanks for the fast reply
Robert

 

[Eric 3.7LX Alpha 1]

Re: 1976 Mercruiser 165 Fires But Wont Run Inline 6 GM

You need 12 volts for Pertronix. Run a jumper wire from the (+) on the battery to the (+) on the coil and start with the ignition switch, see if she fires. Use alligator clips for the jumper, easy to remove when you want to shut the engine off, (also will have to shut off the switch)

 

[GameOnSalmon]

Re: 1976 Mercruiser 165 Fires But Wont Run Inline 6 GM

You need 12 volts for Pertronix. Run a jumper wire from the (+) on the battery to the (+) on the coil and start with the ignition switch, see if she fires. Use alligator clips for the jumper, easy to remove when you want to shut the engine off, (also will have to shut off the switch)

Eric,
Fricken Awesome, Started Right up instantly... with the jumper wire, what do i replace?

Thanks Robert

 

[Eric 3.7LX Alpha 1]

Re: 1976 Mercruiser 165 Fires But Wont Run Inline 6 GM

Your coil is getting power thru a resistor wire or ballast resistor, How many wires on the (+) terminal on the coil and what colors?

Should be able to find full 12V at the electric choke which is fed thru the ignition switch, should be solid purple. Would have to run a wire from it to the (+) on coil.


That jumper wire is handy to keep in the tool box onboard, you never know when you need one.

 

[GameOnSalmon]

Re: 1976 Mercruiser 165 Fires But Wont Run Inline 6 GM

Your coil is getting power thru a resistor wire or ballast resistor, How many wires on the (+) terminal on the coil and what colors?

Should be able to find full 12V at the electric choke which is fed thru the ignition switch, should be solid purple. Would have to run a wire from it to the (+) on coil.


That jumper wire is handy to keep in the tool box onboard, you never know when you need one.

Eric,
Here are a couple pictures of the coil, Brown and white on + side and 2 brown on Neg side... Plus the red and black from pertronix... Here is the pic... if you can explain what i need to do... i will do it immediately... Thank You Sir... Robert

 

[Don S]

Re: 1976 Mercruiser 165 Fires But Wont Run Inline 6 GM

You won't have an electric choke, nor will you have a purple wire. Below is the wiring diagram for your pre BIA wiring.
The resistor wire is the dashed wire between the white wire and the + terminal of the coil
You will have to trace the wire back to find where in the harness it connect to the white wire and cut off the resistor wire. Then use a 16 or 14 gage wire (White to keep proper color coding) spliced into the white wire to reach the coil.

View attachment #2 Eng & Drives 74-77 200.pdf

 

[GameOnSalmon]

Re: 1976 Mercruiser 165 Fires But Wont Run Inline 6 GM

You won't have an electric choke, nor will you have a purple wire. Below is the wiring diagram for your pre BIA wiring.
The resistor wire is the dashed wire between the white wire and the + terminal of the coil
You will have to trace the wire back to find where in the harness it connect to the white wire and cut off the resistor wire. Then use a 16 or 14 gage wire (White to keep proper color coding) spliced into the white wire to reach the coil.

View attachment 151708

Don,
Thank You Sir, I will do that right now... While i had it running It was getting Hot... I shut er down at 190 degree on the muffs... when i touched the top 1/2 of the outdrive it was hotter than hell... Since i don't know or not, i will change the impellar and thermostat today... and hope that cures it... Will re wire today as well... Thank You

Robert

 

[GameOnSalmon]

Re: 1976 Mercruiser 165 Fires But Wont Run Inline 6 GM

Your coil is getting power thru a resistor wire or ballast resistor, How many wires on the (+) terminal on the coil and what colors?

Should be able to find full 12V at the electric choke which is fed thru the ignition switch, should be solid purple. Would have to run a wire from it to the (+) on coil.


That jumper wire is handy to keep in the tool box onboard, you never know when you need one.

Eric,
Thanks for you input my friend... Amazing... It' Works Like a Champ now...Other than overheat issue now.
Thank You
Robert

You won't have an electric choke, nor will you have a purple wire. Below is the wiring diagram for your pre BIA wiring.
The resistor wire is the dashed wire between the white wire and the + terminal of the coil
You will have to trace the wire back to find where in the harness it connect to the white wire and cut off the resistor wire. Then use a 16 or 14 gage wire (White to keep proper color coding) spliced into the white wire to reach the coil.

View attachment 151708

Don,
Located splice, re routed new wire per your suggestion works perfect. Thank you... Now i see i have an overheating issue and the top of the outdrive was extremely hot... After i change the impellar and thermostat i will update on this thread... Hoping its the impellar...
Robert

 

[Eric 3.7LX Alpha 1]

Re: 1976 Mercruiser 165 Fires But Wont Run Inline 6 GM

Good Luck with the rest, glad she's running.

 

[vanashke001]

Re: 1976 Mercruiser 165 Fires But Wont Run Inline 6 GM

I have almost the same exact issue. GM 250 165 HP. Prior owners(teenagers-low 20s)+no winterizing= cracked block. Just replaced it with another one that I know ran. Hooked it up, completed the swap, fires, but will not start. As per your suggestion with the jumper, started immediately. Ran like a dream, for the few seconds I let it. My question is, with a tester using red lead on + of coil and black lead to ground and key "on" we get NO volts. it jumped to 11 when I hit the starter but went back to 0 when the key was just on. Bad coil? or bad test?

 

[Eric 3.7LX Alpha 1]

Re: 1976 Mercruiser 165 Fires But Wont Run Inline 6 GM

I have almost the same exact issue. GM 250 165 HP. Prior owners(teenagers-low 20s)+no winterizing= cracked block. Just replaced it with another one that I know ran. Hooked it up, completed the swap, fires, but will not start. As per your suggestion with the jumper, started immediately. Ran like a dream, for the few seconds I let it. My question is, with a tester using red lead on + of coil and black lead to ground and key "on" we get NO volts. it jumped to 11 when I hit the starter but went back to 0 when the key was just on. Bad coil? or bad test?

Welcome aboard. You have to start your own thread for your issue and not add to someone elses problem. See the attached photo...

 

[vanashke001]

Re: 1976 Mercruiser 165 Fires But Wont Run Inline 6 GM

I apologize, it was not my intention to step on toes. I'm a member of 5 other forums and in those forums they request you search for common threads to post a question on as opposed to starting a new one. Apparently this forum is the opposite. Which answers why there are a couple million posts with 64k in Mercruiser I/O alone. As my question was mostly one seeking a confirmation of sorts, "you did it right/wrong" I thought it would be acceptable especially given it being an identical issue, the only difference being the id of the person asking. Since my question is not unique I'll go back to lurker status and if I have a unique question perhaps I'll post it then. In a new thread of course.