1987 merc 165 ignition problem

[dsamuelson2003]

Can't get the stupid engine to start...turns over fine, though.

I can't get any spark from the ignition coil. I have 12v at the ignition coil + terminal, drops to 10v while cranking over...is this normal? The coil is new. The battery (tested between + battery terminal and engine ground) does the same thing - drops to 10v while cranking.

What's wrong?

 

[Don S]

Re: 1987 merc 165 ignition problem

It's normal for the voltage to drop while the starter is cranking due to the heavy amperage draw of the starter.
No Spark?? You probably need new points, when was the last time you did a full tuneup?

 

[dsamuelson2003]

Re: 1987 merc 165 ignition problem

last tune up was probably 1987 when the boat was made, LOL. It's been sitting for about 10 years, from what the previous owner said, and it's been in "rebuild" status over the past 4.

So if I have voltage at the coil, shouldn't I then be able to see a spark from the coil if I place the coil wire near the cylinder head? Or not necessarily?

Appreciate any extra help.


quote time=1151880748 user=Don S uid=49090 fid=24 tid= rid=1]It's normal for the voltage to drop while the starter is cranking due to the heavy amperage draw of the starter.
No Spark?? You probably need new points, when was the last time you did a full tuneup?[/quote]

 

[Don S]

Re: 1987 merc 165 ignition problem

So if I have voltage at the coil, shouldn't I then be able to see a spark from the coil if I place the coil wire near the cylinder head? Or not necessarily?

Uhhhh, not if the points are glazed over.

last tune up was probably 1987 when the boat was made, LOL. It's been sitting for about 10 years

Do a FULL tuneup, new plugs, cap, rotor, points, condenser, plug wires, etc. Set the dwell, then the timing and if you do it properly, I would bet you 5 cases of beer it will run great.

 

[freddyray21]

Re: 1987 merc 165 ignition problem

I agree. Had the same problem with mine. New set of points it fired and ran great. The points when they close provide the ground to the coil so it will fire. You can run a momentary ground to the neg side of coil while holding the coil wire close to the block to see if the coil fires. Don't ground it for more than a sec or two. You should see a spark if the coil is good.

 

[Don S]

Re: 1987 merc 165 ignition problem

Start a new thread with your question Chad, don't just tack on to someone elses thread with your question.

 

[dsamuelson2003]

Re: 1987 merc 165 ignition problem

Don, you are the man!!! New points and the thing purrs on the first try. THank you!!

But you only get 3 cases of beer so far. Can you help me?

I have read that if the enging does not run, the grey tach wire could be the culprit. Sure enough, if I disconnect the grey tach wire from the neg (-) side of the coil, it runs great. If it is connected, the engine just turns over but does not fire. I hear there are 2 possibilities:

First; shift interrupt wires reversed or bad; but I never changed these even during the rebuild. But the engine only turns over in neutral, and not if I give throttle or change gears. How do I test this?

Second; tach shorted or dead; how do I test this?

You were right on before, what can you tell me now?

THANKS!!!!????

 

[dsamuelson2003]

Re: 1987 merc 165 ignition problem

Still can't get the engine to start with the gray cable on the solenoid! Here's what I have done:

First, checked the tach on the dash: it has 12v and good ground.

Second, disconnected the gray wire from the tach and checked continuity of the gray wire = good.

Then tried to start the engine with the gray wire on the solenoid, but left off the tach. No good, so I am guessing that the tach is not the problem.

Last, I checked the shift interrupter switch: when in neutral, there IS continuity - the switch is open. Is this right or wrong?? Why won't the darn thing start with the gray wire attached??????

Please help....anyone.