Thank you! Is this information from the Mercruiser Service Manual #36 (ECM-555 Diagnostics)? Not sure which one I need to purchase, I've found them on ebay. Heading to the lake later today to test drive.

When you get a lot of radical alarms check and clean your grounds, especially the ones on the block that ground the block to the battery.

I had a situation similar to yours, cleaned the 2 GA grounds on the block and the problem went away.... This is good/bad. Its hard to diagnose BUT it really cheap to fix.

I can clean all day! Your right, its cheap!....today, received the same two faults after cleaning the grounds (X2). I did notice on the scan tool the oil pressure reading was 70 PSI however the gauge was reading 40 PSI. I'm going to replace the oil pressure sensor.

Fault 84 Oil PSI CHK HI
Guardian Fault #9

Hey no one jumped in again. I'm having your initial problem. Thought it was a bad fuel injector connector because of fault code changed, same problem..... I thinking it might be fuel related, maybe fuel cooler filter...Ed

Thanks Ed, I'm planning to replace the oil sender and oil sensor. Hopefully this will solve the issue. Having the scan tool has helped.

Further update,,,,, We found a problem with the temp sensors in the exhaust manifolds. I have Miami marine stainless and their position in the manifold at higher settings is causing an overheat/guardian mode fault. The owner has agreed to reposition the sensors to avoid this problem that he is aware of..

Two beep per minute issued solved. After replacing all the sensors and purchasing the Rinda Scan Tool I finally solved the issue this weekend. The Rinda indicated Fault 84 - see ealier posts, but all sensors had been replaced, connections and wiring checked and cleaned. Purchased oil sender and still had the two beeps. I purchased a new oil pressure sensor for the second time and noticed the one that I had purchased from the repair shop earlier was different than the one I purchased this weekend. The newer being the correct sensor. And you know the rest of the story....I installed the wrong sensor two months ago (this was the one sold to me) which was causing the fault. After installing the correct senser the two beep issue was solved. The Rinda really helped solve the problem with the ability to read realtime data from the ECM to include monitoring oil pressure while underway. Thank you to everyone who responded to all my questions! Now hunting for the right prop! Need more speed!