Merc motor misfortunes

JDC · 10-24-2009, 06:41 PM

Hello Mr. Boat Dr.

I have had 2 boat mechanics check this problem out, but they haven't been able to fix it, I hope you have a suggestion for me that can.

I have a 1976 115 merc inline 6 out board motor that blows rectifiers.
a dead short was suspected but I by-passed the eletrical to isolate the motor and it still happened after aprrox. 20 min. of run time.

With a fresh rectifier it will run great, I don't take it past 4500 rpm but it will run for approx. 20 min, after that I can't get more than 2200-2400 rpms. I'll replace the rectifier and the same thing happens again.

Help!

Thanks,

Jim

wanabefishin · 10-24-2009, 06:53 PM

I think I must be blind because I can't see where I would post my own thread. Can you let me know how I post my thread? I don't know anything about boats too help you, sorry.
Thanks Phil

fishkisser · 10-24-2009, 08:01 PM

Maybe it would help to post this in the boat doc thread ...
Its at the top of the boat and motor section ...

If you cannot find a shorting hot wire to ground
it could be an internal short in the stator or rotor
and possibly the trigger or rectifier ...

budnate · 10-25-2009, 07:26 AM

Call Dave at Sky Valley Marine in Monroe Wa, guy knows Mercs, and really knows the stack 6's, willing to bet he will know what's up.

tell him Bud sent ya.

Orca · 10-25-2009, 11:42 AM

wanabefishin:

Boat Doc' · 10-26-2009, 08:20 AM

Quote:

Originally Posted by JDC

Hello Mr. Boat Dr.

I have had 2 boat mechanics check this problem out, but they haven't been able to fix it, I hope you have a suggestion for me that can.

I have a 1976 115 merc inline 6 out board motor that blows rectifiers.
a dead short was suspected but I by-passed the eletrical to isolate the motor and it still happened after aprrox. 20 min. of run time.

With a fresh rectifier it will run great, I don't take it past 4500 rpm but it will run for approx. 20 min, after that I can't get more than 2200-2400 rpms. I'll replace the rectifier and the same thing happens again.

Help!

Thanks,

Jim

The rectifier has nothing to do with how the engine runs. It only charges the battery. Possible problem could be the stator which besides supplying high and low voltage to the ignition also supplies voltage to the rectifier.