New Battery Charger - 1998 450DA

My original ProMariner 60 was only sending 3.1v to my battery banks so I replaced it with the new model. Its not working and Promariner says that it's not seeing the batteries. Evidently older chargers needed a battery isolator between them and the batteries, but this is no longer necessary.
I have documentation on my isolator (had to have it replaced a few years back) and see the engine alternators feed in here. I'm a little hesitant to "eliminate" this piece of equipment - nightmares of 14v from the alternators crashing into 14v from the battery charger dance around my non-electrical engineer mind.
Anyone have experience upgrading a battery charger on an older SeaRay? Seems that both alternators and charger should directly "see" the batteries. I can force the charger to work by bumping a starter (must open a circuit) and I see the charger back off of delivered amps when the engines are running.

Is the charger not wired direct to the battery(s)? if so, nothing else in the battery/charging system wiring, matters.

I replaced the same unit in my 1994 440eb with a master volt unit. Plug and play, no issues.

Check if the fuses or breakers between the charger and the batteries are blown.

My 400 DA has resettable circuit breakers between the battery charger and the battery, but they are located behind the circuit breaker/ disconnect panel in the cockpit. If they are blown you would have this problem.

Good Luck,

Pete

Many new chargers come with inline fuses already on the charge leads, right at the battery terminals. IMO, I would bypass the boats original breakers, and wire the new charge leads direct to the battery(s). This eliminates extra connections and redundant circuit protection, not to mention, breakers can go bad with age. On a 1998 boat, the 19 year old breaker would be very suspicious.

Have the same boat you do. Replaced my original
ProMariner with a new one about three years ago without any issues. The new one works great and has added 2 years to the life of my batteries.