Cat 3412 1997 problems

Sorry to hear this is starting to sound like a more involved issue. Curious though on what the plan is to get it fired up? Is the thought that the rust is enough to cause the slow cranking and some PB Blaster will somehow resolve that enough to get her to crank and fire? Doesn't sound logical to me but I guess it's worth a shot.

Did you pull an oil sample yet for analysis? What else other than water in your oil could introduce water to all the heads and cause rust under all four valve covers?

How do you know it is not hydro locked?
Fuel locks up lungs also, Washes away oil from internal parts, ie valve covers and cylinder walls.
Stuck valve(s) or leaking exhaust riser can contribute issues also.

Been thinking more about what I last typed.
While the valve covers are off, bar the engine over. Every 30° grab every rocker. Either rigid or just barely loose (lash).
Make a check list to keep track.
Over two complete turns of the crank should do it.
Every one should have lash and no lash.
Looking for a sloppy loose rocker arm or one that does not have any lash when all up (stuck or broken)..

If all valves close yet still have lash, then you can try to spin it up with the starter.


Results on the oil samples yet?

What are the details of your boat - type, year, make, etc. ?

As for the batteries, I don’t know of any meter that can tell you how many amps are in a battery. You can read how many amps are being drawn out of a battery or how many amps are being put into it with a charger. But not the amp condition of the battery itself at rest. I have a shunt and meter that reads how many amps are being drawn from my batteries but it reads as
-xx amps.
So if you are showing 26.7 volts that sounds normal. Doesn’t mean the batteries are good, Volts just one measure. But it’s a good sign. I would turn your charger off, wait awhile, and see what the volts and amps do. Do you have anything else that uses the starting batteries?

8D batteries deliver between 1000 to 1250+ cold cranking amps.
Your 3412s probably require 700 to 900 CCA.
In series, it is 24 volt but still the same amps as the weakest battery (weak chain link).
Two fresh 8Ds should turn you over fine, of course pending good battery cables, switches, solenoids and connects.
Many issues have been found in these overlooked components.