I am looking to install a 1500w inverter onboard, predominantly to power microwave when away from berth. I am looking at a pure sine wave model, and will wire into the main rcd breaker box with an ac changeover switch. The one area which seems a little vague is the methodology for grounding. My 895 does not appear to have a common ground plate installed on the hull. Do I simply connect the ground to the negative dc on the battery. I have sought electrician advise, and from invertor supplier, but answer seems to be 'depends on your boat wiring layout'. I will likely get an electrician to install/check anyway, but would be keen to understand how anyone has successfully done this on a merry fisher, as I'm not convinced from the experts I have spoken to to date.
I was planning to install an invertor and technicians made an inspection at the boat. They were planning to connect grounding to negative of house battery as far as I heard. Same as you, I could not locate the grounding bar described in boat’s manual.
Now I have the similar case. I decided to postpone to install an invertor (as my batteries will not be enough anyway) and bought a 12v 135watt portable invertor. It is enough to run a noteboook. However, the manual advises to ground it (it has a small grounding point). It is not practical to get a long wire to connect battery negative so I decided not to use it until I find a safe setup. It works without grounding (I tried at my car) but safety comes first.
The 'common ground' bus bar is behind the galley (right next to the kitchen sink drainage hole). It's not something special - just a HD busbar (I think ~300a) with all the negs from batteries, engines, windlass, charger.
For the proper grounding, I was told, galvanic isolator is needed. Otherwise our sacrificial anodes do the heavy lifting and provide grounding-on-water.
My boat is connected to shore power 24/7 and I do see the wear and tear. No inverter yet but it's planned.
I am not aware of the grounding of the inverter or the mains input on a Merry Fisher but certainly a Jeanneau SO42DS does not connect the mains (or inverter) ground to the DC ground at all. It is isolated from DC ground and so therefore is isolated from the seawater, making a Galvanic Isolator unnecessary. It could be installed but would serve no useful purpose. I am only discussing the grounding convention for the Jeanneau sailboat so please understand the power boat may have a different convention.