Mercury 150 Four Stroke charging

[MaineTyee]

Hi all, new to the forum and need to draw on the expertise here. I have a Lund Tyee 1900 with a 2015 Merc 150 Four Stroke. On a fishing trip in September I slowly started losing voltage and eventually the motor died. Luckily I had a 9.9 Pro Kicker to get me back to the dock. I assumed it was the alternator and bought an aftermarket replacement. I had not run it since putting the new alternator in and decided to start it on the muffs to check the voltage before shrinkwrapping it for winter.
I had to boost it to start, then checked the voltage at the battery and only got 11.3 volts. When checking at the alternator post I am getting 21 volts!
I know 21 volts is too high, and now it seems I must have blown some sort of over protection component. Any ideas? Thanks in advance for any input.

 

[Bondo]

Ayuh,..... Welcome Aboard,...... Let's try the Merc Outboard forum, 'n see if we can get ya an answer over there,.....

 

[MaineTyee]

Self diagnosed...need another new alternator with a better voltage regulator, and the alternator output wire has a 100 amp fusible link in it that was blown

 

[QBhoy]

Hi. Did you jump start it with a running engine on the other end of the leads ? Doesn’t often end well perhaps.
I have a similar aged 115 merc. The output charge it has is very low when at idle and first started. Takes a wee while to give a charge out. Then it can actually regulate to provide a higher charge at slow trolling speeds, if it needs to. But certainly initially…it doesn’t snow much…unless you wait or give her a wee bit of revs for a few seconds

 

[Bondo]

Self diagnosed...need another new alternator with a better voltage regulator, and the alternator output wire has a 100 amp fusible link in it that was blown

Ayuh,...... I'm wonderin' whether that's what caused the original problem,..??......

 

[QBhoy]

Ayuh,...... I'm wonderin' whether that's what caused the original problem,..??......

Or the jump start