Mercruiser 4,3 MPI from 2008, intermittent alarm after 3500 rpm??

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May 7, 2021
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Not sure there would be an alarm for high oil pressure. But that pressure recorded is ridiculously high. What’s the temperature reading at ? If it’s running cold with a full open thermostat, it could be that high perhaps.
Hi! I'm currently running without a thermostat, so fresh water cooled directly. Do you consider the oil pressure to be too high? What would be a reasonable pressure level at ca 3500 rpm?

Any idea on what could cause the high oil pressure?
 
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May 7, 2021
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Go to the shift plate and look for the in-gear switch. If its there, unplug it and the issue should go away

View attachment 339655
Heading out to the boat today again. Before I remove it, what is the purpose of the in-gear switch. Could I harm the engine in anyway by removing it?

I thought the alarm indicates that something is malfunctioning. Your hypothesis is that the gear switch is broken?

Thanks
 

alldodge

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Disconnecting the switch will do nothing to the motor. It can be left disconnected for ever even if it is not the problem

The switch is on top see post 4
 

alldodge

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The ECM has a setting that was programmed to sound the alarm if motor is in neutral and exceeds a specified rpm. That's all its for
 

QBhoy

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Hi! I'm currently running without a thermostat, so fresh water cooled directly. Do you consider the oil pressure to be too high? What would be a reasonable pressure level at ca 3500 rpm?

Any idea on what could cause the high oil pressure?
Running cold will cause the oil to remain viscous. Can also damage your engine too. When up to temp and around those rpm. You should likely be around 40-45 psi, I’d think. Should think about getting that thermostat in ASAP.
 
Joined
May 7, 2021
Messages
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Go to the shift plate and look for the in-gear switch. If its there, unplug it and the issue should go away

View attachment 339655
The winner is @alldodge! The problem was a malfunctioning in-gear switch/shift plate. The engine "thought" it was running in neutral when in fact the shift was in gear. So it sounded an alarm when high rpm when "in neutral"...

Thank you for all your help!!
 
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