TOPIC: AGM battery with old "Tower of Power"

I have a 1979 Mariner 115 inline 6, I've read that it's a bad idea to use an Absorbed Glass Matt battery like an Optima with it. The reasoning is the charging system uses the battery as a voltage regulator and the AGM battery can't regulate the pulses and will damage the charging system of the motor. Is there any truth to this? I have a Seapower Marine battery from West Marine and also have a new Optima Blue Top. I'd prefer to use the blue top but not if it's going to hurt my motor.
Thanks in advance,
Scotty

Hi Scotty, here's the thread where that subject was discussed;
www.fiberglassics.com/fiberglassics-forums/home/main-forum/what-s-the-deal-with-marine-batteries#25410

Thanks,
Anyone want to buy a blue top?