limp mode coming off plane

[dvx216]

So my port 8.1 when coming off plane will start beeping and will go into limp mode. Oil pressure on gauge is fine. If you shut motor off and start it back up it's fine. Checked for codes and there wasn't any. My only thought would be bad oil pressure switch.

 

[Lazy Daze]

Hard to say. Could be water pressure, too. Have someone with a real Merc computer hook up to it - the sensor that was complaining will be logged in the history. Keep in mind that it could be a flaky sensor or an actual issue. The code gets you into the right system - but then you need to put on your mechanic hat and diagnose.

 

[skibum]

I fought this same problem a couple of years after I bought my boat. I hope you have a different issue, but the cause of mine was a restriction in the water inlet tube going through the transom. My symptoms were that the boat would get up on plane and run all day long at 3450 RPM. If I tried to run above 3500 RPM for more than a couple of seconds, the Guardian mode would kick in. On particularly warm days, it would cruise at 3450 all the way across the bay, and then do the Guardian mode thing as I dropped to a lower RPM coming off plane.

Super simple to check if you have access to the top of the transom assembly where the water inlet line from the seawater pump connects. You're looking for one of these:

Remove the 2 bolts holding it on, and see if it looks anything like this under there.

If it does, you need a 32-8M0090859 - Hose Kit.

Good luck!

 

[Lazy Daze]

Excellent post with great info, Ski. But... he has v-drives

 

[skibum]

Dang! Missed that. I'm outta practice.

 

[Bill Curtis]

Water pressure sensor in the line between the raw water pump and the 1st oil / PS cooler maybe?

Look on youtube and there are videos showing what to do to check / clean the port in the water line manifold.