New member with first 47' commander with Detroit 8v53. I took it out this weekend and parked in a cove so kids could swim around. when throttled down from 11 knots the alarm went off on the starboard engine. So I jumped down and shut it off. Tried to crank it a few minutes later and the alarm stayed on. I let it sit for an hour or so check the oil and all was fine. Hung out for a few hours and then fired both back up and drove fine back to the marina. When docking at marina once pulled back on throttles for wake zone alarm went off for a second and then quit. Pressure on gauges is fine. I am thinking the sensor is bad as it only seems to do it when drop from throttle to idle. Don't have much experience with this particular diesel but is what makes sense to me.
Had the same exact problem and replaced the oil pressure sender. Not sure what the root cause of the problem was (stuck sender?).
perfect I assumed that was the issue but figured the wealth of experience on here would verify.
My 47 did this the first few times I took it out. After the 3rd time we had it out - we never had that issue again. It had been sitting without use for a while so perhaps that had something to do with it.
I wondered about that she has been sitting for two years except one run to the yard for bottom repaint. So many things don't work but motors run and she drives
There are oil pressure senders that go to the oil pressure gauges.
There are also low oil pressure switches that will trigger the alarm. They come in various pressures.5,10,20,and 27psi.
I personally prefer the 10psi on the Detroits as the 5psi is pretty low and not much warning that something is going wrong.
The Detroits are also notorious for having low oil pressure at idle when hot so your alarm going off might be a nuisance alarm or the switch might be getting weak.
Here is what you likely need:https://dieselpro.com/detroit-diesel-parts/8v53-engine2/solenoids-s...
Replace the senders with the 5 psi version. This was always a problem on Detroit’s even when they were brand new, if you come off plane straight to idle they’ll ring the alarm bells temporarily on the 10psi ones until the oil cools down. I switched to 5psi for this reason. They never ring now. Which is fine for a 500 rpm idle. Rule of thumb is at least 1psi per 100rpm. The cause is the unique 2 cycle oil requirements you can only use straight weight so it gets thin when hot.