What's the procedure

[Dellonn]

Hey Guys:

What's the procedure for checking the charging system on a 1977 Mercury 1500 150horse Inline 6. Serial # 4752370.

I suspect my engine is not charging my battery. But my tachometer still works fine. The other day when I pulled off the positive cable to re-wire the lead for the bilge pump the engine stopped running. A. Is it supposed to do this? and B. Did I screw something up by doing this while the engine was running?

 

[Jeff_G]

Re: What's the procedure

You probably didn't hurt anything.
The 1500 is a battery operated ignition. To check charging the simpliest way is with a volt meter.
Check the voltage engine off. SHould be appox. 12.5vdc
Start and run the engine above 2000 rpm you should see an increase in voltage.

 

[Moody Blue]

Re: What's the procedure

Hmmm, removing the battery lead from a running motor with battery CD ignition will usually kill the rectifier (and possibly damage the switchbox and/or trigger. If the tach is still working then maybe only 1/2 of the rectifier (1 diode) was damaged.

Yes your motor will stop running if you disconnect the battery. Newer generations of motor don't rely on the battery for the ignition system but the older ones do.

As stated, the battery voltage should be 14V+ with the motor running and about 12.7V with the motor off. You can measure at the battery or at the rectifier output.

 

[Faztbullet]

Re: What's the procedure

Pulling cables is the quickest way to spend money on these engines as MoodyBlue stated it can damage trigger and switchbox.

 

[Dellonn]

Re: What's the procedure

Ok, and the check / fix would be? ....

 

[Moody Blue]

Re: What's the procedure

Depends.

If motor is still running then you are lucky.

To check the rectifier, do a search in this forum and you will find the procedure. Search "rectifier test".

Have you measured voltage, running and not running yet?

 

[Dellonn]

Re: What's the procedure

I'm replacing the water pump, almost as we speak. I got rained out. My splines are not lining up trying to re-install the lower unit. I'm in forward gear on both lower unit and shifter dealy thingy (that's a technical term). I've gotten the unit up to where the bolts are flush with the bolt holes. I've turned my prop counterclockwise over and over with no luck. I'll keep trying when the rain stops.

The boat will run tomorrow (provided I get that pesky lower unit in place). I'll check voltage. Non-running i'm at 12.8volts

 

[Chris1956]

Re: What's the procedure

Turning the flywheel is a lot easier to line up the splines. I also reinstall the gearcase with the controls and gearcase in neutral. I find it easier, since neutral is a single position, versus the movement inherent in the shift shaft in forward. Make sure the upper shift rod guide(plastic casting) in in the midsection, versus the LU. That holds the upper shift shaft in place for you.