So i have a 1989 272 SR1 with 350 mag alphas. Yesterday i did the impeller in the lower drive and i was using the trim and running the radio and everything was fine. Today i went to change the oil and when i trimmed the drives down they were sluggish and slowly dying out as if the batteries were dead. I checked the batteries with a meter and get 12v on both. I started both engines no problem they cranked right over. And while they were running i still had sluggish trim and lost power to my amp completely. The trim pumps will only click now. They are acting like the batteries are dead. Not sure what would cause this. Any ideas? Also i checked fuse for the amp and it’s good. The trim pumps have power at all times even with the battery switch off.

check the positive and ground connections...most likely a ground needs cleaning or fixing...

You definitely have ground issues. Very common...

full charge should be around 13.5 v, Id load test the batteries could be shorted cells.

It is a boat... by definition the issues never end

Check BOTH batteries. My Formula had the trim pump wired to one battery. If you ran the engine on one battery, it wouldn't charge the other, which may be the battery the trim pump works off of. Also, full battery @ rest is 12.6V with no drain on the system. 13+ running

So i checked the voltage again when i got home because I’ve been suspicious of a draw. Sure enough the battery that powers the trim was down to 9 volts. So the thing is, my battery switch was off. The only thing that works with the battery switch off is the trim pumps. Does anyone know if all formulas are wired that way? And how can i diagnose/fix a parasitic draw from my trim pumps

Check for a draw through the cables with an ammeter. If it shows a draw you have to find it obviously. If not be aware that a bad battery can discharge internally with nothing hooked to it.

Charge the dead battery. Then test for a drain. You may have been running the trim pump off the battery that was not being charged ,while you ran the engine. In other words, you may not have a problem. Just alternate batteries. Also, on my 330, the radio memory is only hooked up to one battery. When it was new to me, I went nuts trying to fix the radio. It turned on, but didn't work because the one battery that supplied the memory power was bad. What an adventure!!!