questions on mid 80's 35hp merc.

tsbrewers

Cadet
Joined
May 30, 2015
Messages
15
Hey All, I recently picked up a used pontoon that has a mid 80's Mercury 35hp. I haven't had it on the lake yet, but it seems to run well, but doesn't seem to charge the battery. Also, I have a brand new (deep cell) battery and when i try to start the motor, it only cranks a few times before the battery won't kick it over. I can pull it off a charger, crank the cold motor for 10 seconds, then it won't crank after that. If I put the jump starter on the battery it kicker over extremely well. Once the motor is warm, it starts very easily.

I tested the stator, and it seems okay. It has resistance (don't recall the number) and does not have continuity to ground. I replaced the rectifier and still can't get anything more than 12.5v or so at the battery, even at half throttle?

So looking for suggestions on where to go from here? I did clean every connection on the motor that I could find and am stumped.
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,721
Do you know the value of the AC input voltage at 1000 rpm? Since you know or apparently know the resistance, maybe you know that too. You can measure it and it should be somewhere around 16 - 18 vac with an RMS reading meter which most current digital meters register. The output of the rectifier should be up around 16volts if unregulated. Don't know if 35 hp engines had regulators or not. Otherwise it will be around 14.5v at 1000 rpm at the red output terminal of the rectifier/regulator module. If you have voltage there, is it wired to the battery wire which is usually the large input wire on the starter soleniod.....convenient junction point?
 

tsbrewers

Cadet
Joined
May 30, 2015
Messages
15
I ended up dropping it off at a local boat guy a couple days ago, hopefully he can figure it out. Thanks for taking the time to answer.

Brew
 
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