Grounding Through Anode

This query relates to a 55 foot glass fiber ketch which is being used to monitor for porpoises acoustically. Porpoise produce ultrasonic clicks and this means that we may be more vulnerable to high frequency noise than the normal user.

We are suffering from a lot of electrical interference on our monitoring equipment which has prompted us to look at the vessels electrical system for potential causes.

Two issues with the ground raise concerns.
1. An aquadrive has been fitted, which presumably means the engine is no longer earthed through the prop-shaft

2. The main earth is now a fairly large anode. Some electrical engineers hold that his is fine, but I’m suspicious of this as being the vessel’s main earth.

Any comments or suggestions will be most gratefully received