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takeahiketour

Oil Pressure

4 posts in this topic

I’m idling at about 38 gets up to 55 when I open it up, then drops to just below 20 after a long run. Normal? Merc 350 Mag MPI

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Sounds about right. What oil are you using.

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6 hours ago, mpm330 said:

Sounds about right. What oil are you using.

I believe it was Quicksilver 25w40 full synthetic, whatever was recommended by Mercury...

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3 hours ago, takeahiketour said:

I believe it was Quicksilver 25w40 full synthetic, whatever was recommended by Mercury...

For a 2005 216 Sunesta, your boat will have Faria analog gauges meaning the oil psi readings are being sent by the mechanical oil pressure sender, while the ECM is getting it's oil psi information from the oil pressure sensor and as such the 2 are on different circuits.

If for example your engine was using a mineral 10w30 engine oil, on long runs above say 4000 RPM you could expect to see some wild oil psi fluctuations on the oil pressure gauge from the oil foaming up. This would be accompanied by an audio alarm being turned on by the ECM when it found the same readings. Hence MerCruiser recommends 25w40 semi-synthetic and Volvo uses 10w40 full synthetic - the heavier grade and additive package resists foaming under the loads experienced with a marine engine.

Sounds like your oil pressure readings are okay to me too.

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