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idrabefi
06-02-2021, 11:24 AM
Having issues with high pressure (15 psi with key on but engine not running, 50 psi at idle, and 75-80 psi at full throttle) on a 5.7 Indmar with about 300 hrs. The idle and throttle psi's were with warm engine (160 F). Running Mobil 1 filter and Rotella 15W40 oil (yes, the diesel version). Changed sending unit (both old and new were 240 ohm without engine running, but changing was the easiest/quickest resolution attempt) and still have same issue.

1. Should the dashboard gauge read 15 psi without it being turned over? This is the case even with the oil cap and dip stick removed. If the gauge
should read 0 psi when gauges on but engine not, can the gauge be reset/fixed?
2. What should I look at next?
3. Should I even be concerned? Lots of forum chatter regarding concerns with low pressure, but not many seem to be overly concerned with high
pressure.

Appreciate everyone's review/feedback.

Branden967
06-02-2021, 11:46 AM
Ironically sort of dealing with that same question right now also. When I drained / changed the oil, I fill it up 75% and then top it off when its totally level / in the water. My concern is when I change it I dont get it all out and then ultimately Im worried about it being overfull. On my gauge when Im up to speed mine reads 70-ish PSI at anything above 25mph and then at idle it bounces around 40-50PSI.

Im not as concerned with that gauge as I am with what it reads on the dip stick and boat level. My dipstick oil level is towards the top 90% ish full on that metal gauge.

Adding boat is a 2008 OBV.

idrabefi
06-02-2021, 01:46 PM
I change oil in fall and top off after engine warms up in spring. Adding really didn't affect pressure much on dashboard gauge. Interested though if your gauge reads any psi with key on but engine off.

Branden967
06-02-2021, 02:11 PM
Im pretty sure it reads zero when everything is off.

z28ke
06-04-2021, 08:25 AM
When the engine is NOT running the gauge should read zero. If you turn the key to ďonĒ and it jumps up to 15psi without starting the engine, then itís either the gauge, sender, or wiring. Since youíve replaced the sender with no change Iíd look at the wiring and/or gauge if you really want to correct it.

In all honesty I donít think itís a big deal though. If you make 15psi the new 0psi, then all your readings look fine. 50psi becomes 35psi, 75psi becomes 60psi, etc.

Holdmybeer
06-04-2021, 08:59 AM
The gauge is getting additional voltage from somewhere and it is making the pressure read 15psi. Once the sensor sends the actual voltage it is additive and looks high. Check the wiring in the dash on the gauges.
I would bet there are several loose nuts on the back of the gauges and grounds and you are getting a false reading.
If the oil level is right and you aren't blowing oil out in the engine compartment and there is not oil in the water then you are fine.

z28ke
06-04-2021, 11:18 AM
The gauge is getting additional voltage from somewhere and it is making the pressure read 15psi. Once the sensor sends the actual voltage it is additive and looks high. Check the wiring in the dash on the gauges.
I would bet there are several loose nuts on the back of the gauges and grounds and you are getting a false reading.
If the oil level is right and you aren't blowing oil out in the engine compartment and there is not oil in the water then you are fine.

Yep, I was thinking grounds as well