A couple of weeks ago I went out for the weekend and after about 40 minutes of hard running with a heavy load my Optima Blue Top blew the vent cover and was steaming. I changed to my other battery (same kind) and it gets hot also.

Today when running it gets really hot. Almost to hot to touch and small amounts of moisture is on top of the battery.

Any idea whats going on.

History on engine before this happened I dont seem to recall any issues.

I did install IM heads right before this. Dont see that causing this but while I had the flywheel cover off the flywheel was pretty rusty. I cleaned the rust off and put her back together.

check the volts with the motor running...

is it a cdi motor?

Check your ground it sounds like a high resistance short. If you peal back a little of the wire insulation is there any corrosion in the main pos and neg cable?

yeah some sort of ground issue

Might be a good idea to get an amp clamp and amp the main pos and neg cables to see how many amps it is drawing. Check all connection by the starter, any circuit breakers neg connections at the motor. Clean the crap out of all connections with a small wire brush till they are shinny.

Finally had a few minutes to mess with this.

Checked Volts with engine at 4200 RPM hooked up to battery and its putting out 19.5 volts.

Checked Volts with engine at 4200 RPM unhooked from battery and its putting out about 27.5 volts.

Both of these seem way to high right.

yep..

idk if they have a voltage regulator or not... but with that many volts you boiling that battery... go see a mechanic

Bad regulator.

I'm not a battery guru but yes that seems high. I can only compare to what my outboard puts out which is 14.4 volts.

I'm sure someone else will chime in with more info.