TOPIC: 1970 1350 Rectifier

I was on my way to the Toms River Antique Boat Festival yesterday morning, cruising along and the engine just shut down. Smoke was coming from the cowl so I immediately shut off the power at the main battery switch. Long story short, I popped off the cowl and could smell immediately it was something electrical, sure enough the rectifier is melted. I’ve replaced them on other outboards, just never had one fail like this. I’m worried there is a deeper issue. I guess for now the best thing is to replace and monitor. Up until now I’ve used the boat maybe a dozen times. I’ve put maybe 20 hours on it and it’s always run like a top. Now to see if I can get one from a local shop or if I have to order one. Sorry the pics are sideways.

make sure it is clean under the rectifier. so, it dissipates the heat.

Ok so I replaced the rectifier with a CDI unit. Now it sounds like it’s missing when I try to start it. The engine has never been hard starting, always has fired right off since I’ve had it. The video file of it cranking over must be too large to post. I cut back to clean wire. Also notice some other wires that I will be replacing. Im afraid more damage may have been done than just burning up the rectifier. The boat is currently docked at a friends house, my new plan is to try and get the kicker engine running to make the 3 min drive to the ramp so I can get the boat back to my house. Any ideas or input will be greatly appreciated

Inspect your yellow stator wires coming down out of the stator to the rectifier, and the red (Positive 12vdc) wire from the rectifier to either the internal harness (original set-up) or if modified to connect to the starter solenoid's primary Positive 12vdc terminal,...For unwanted contact with engine ground, which would cause your "melt-down".
Then Ohm test the stator's yellow (only) wires to determine if your stator is still okay.
The little original rectifier is nor regulated, and if you were cruising an unusually long distance, compared to your normal use, the rectifier can build up a production of 18+vdc, which can not only over-heat the rectifier, it can eventually cause ignition failure on the '70s CDI style Merc ignition.
If you find your stator's charging system has survived,...I strongly encourage installing a Mercury regulator with a built in rectifier.
They are expensive - new - but "rarely" fail, so most likely a used on off eBay will work for you.
The Mercury Marine part number is 88307T, or 8M0084173
This regulator will keep your charging system to a limit of 13.8 or 14.2vdc depending on its vintage - when purchased used on eBay, etc.
Yellow stator to Yellow rectifier
Yellow stator to Yellow rectifier
Both rectifier reds to your primary Positive on your starter's solenoid
Black to engine ground (-) negative
Gray rectifier wire can be connected to your Brown tachometer sender wire, OR don't use this gray, and connect your tachometer sender wire to either stator yellow, IF you have a later model tachometer that senses off the alternator (stator),...OR leave it attached to the starboard side switch-box Brown terminal if you are running an original Quicksilver tachometer.
doc

Thanks for the input Doc! The yellow wires are definitely in need of replacement the ones circled in the photo. I believe the wires from the stator are ok, but will inspect further once the boat is back to my house. I was in fact running a longer distance than I have ever run the boat before, and at a higher rpm than usual when it died too. Most of my runs have been between 15 and 25 min or less at lower rpms. It’s usually more choppy out and I have the rest of the family on board. This particular morning was calm and it was just me and two of my sons(ages 8 & 9). I know these inlines run well at higher rpms so I was trying to “stretch its legs” a little. I was probably running at 4500 rpms, the tach has never worked so I’m not exactly sure, but definitely no higher than 5000 and there was plenty of throttle left. The red wire seem to be in decent shape. I cut back all the burned wires till I got clean copper.