PDA

View Full Version : oil pressure gauge all over he place


Tazz2503
07-21-2010, 03:12 PM
I just bought a used 2001 205V. While out yesterday the oil pressure gauge would fluxuate like crazy. at idle it would go down to 5lbs, aound 2500 rpm it would be 40 and and high RPM it would go up to 75. Anyone had this problem? should I start with the gauge or sending unit. Could it be a engine problem?

deminimis
07-21-2010, 03:23 PM
Not sure about the 5# reading, but 40 to 75 seems normal.

russlars
07-21-2010, 03:34 PM
Most likely the sender. Mine did the same thing and the new sender took care of it.

deminimis
07-21-2010, 03:53 PM
What I had always believed is the very general rule of thumb is 10-15 PSI per 1,000 RPMs. That includes at warm idle (800RPM at 10-15 PSI -remember, I said "general rule of thumb"). Your 5 PSI reading is concerning if accurate. I'm with russlars all the way. Swap out the sending unit with a new one (cheap, quick and easy). Hopefully that cures the low reading. I should note I assume you have a SBC-based engine.

Tazz2503
07-22-2010, 01:39 PM
Thanks for your input, I'm going to start with the sending unit and see how it go's.

19_Skier
06-06-2012, 08:35 AM
For the sake of not posting another oil pressure thread, this is similar to the situation I had on the weekend.

While out cruising I noticed my pressure was bouncing quite a bit between approximately 10 and 40 (never below 10) - boat was just in gear, no throttle. Once I applied some throttle pressure would stabilize and climb normally to just under 80 at WOT.

Based on the information I have read here it seems like I am in need of a new sending unit. Would I be better served to grab a gauge reader first to confirm the actual oil pressure before spending money on a new sending unit?

Secondly, it seems like a pretty quick fix that I could do myself (changing the unit) however, I have no clue where it is located. A "road map" would be greatly appreciated - 2001 310hp predator.

TNPIG
06-07-2012, 10:43 AM
For the sake of not posting another oil pressure thread, this is similar to the situation I had on the weekend.

While out cruising I noticed my pressure was bouncing quite a bit between approximately 10 and 40 (never below 10) - boat was just in gear, no throttle. Once I applied some throttle pressure would stabilize and climb normally to just under 80 at WOT.

Based on the information I have read here it seems like I am in need of a new sending unit. Would I be better served to grab a gauge reader first to confirm the actual oil pressure before spending money on a new sending unit?

Secondly, it seems like a pretty quick fix that I could do myself (changing the unit) however, I have no clue where it is located. A "road map" would be greatly appreciated - 2001 310hp predator.

Same thing here. Could someone give me a roadmap to replace the sending unit on my 84 S&S. Also, my engine hour gauge is working either. What should I look for there? Thanks

19_Skier
06-18-2012, 10:12 AM
For the sake of not posting another oil pressure thread, this is similar to the situation I had on the weekend.

While out cruising I noticed my pressure was bouncing quite a bit between approximately 10 and 40 (never below 10) - boat was just in gear, no throttle. Once I applied some throttle pressure would stabilize and climb normally to just under 80 at WOT.

Based on the information I have read here it seems like I am in need of a new sending unit. Would I be better served to grab a gauge reader first to confirm the actual oil pressure before spending money on a new sending unit?

Secondly, it seems like a pretty quick fix that I could do myself (changing the unit) however, I have no clue where it is located. A "road map" would be greatly appreciated - 2001 310hp predator.

Had a chance to poke around this weekend and located the sending unit. Planning to swap it out next week, is there anything I should be aware of before taking it off - I thought I read something in another thread about being careful when removing but can't find that thread!

Rossterman
06-26-2012, 02:17 AM
Having tne same issue. Let us know if you solveed it with the sender

j.mccreight@hotmail.com
06-26-2012, 11:28 PM
Don't know if it matters but indmar says.

Oil Pressure at Idle 4PSI Minimum - Hot 5 PSI Minimum
Oil Pressure at 2000 RPM 18 PSI Minimum Hot 10 PSI Minimum

Analog Oil Sender Resistance
Oil PSI Resistance (Ohms)
0 psi 227-257 ohm
20 psi 142-162.5 ohm
40 psi 91.7-113.6 ohm
80 psi 9-49 ohm

CCAnderson
06-27-2012, 10:16 AM
small block chevy engines are notorious for low oil pressure especially after they wear from hard use. just remember the flow is more important than pressure but to low of pressure means that it is time for a rebuild because the bearings are worn out.

Rossterman
06-27-2012, 11:00 PM
I think the issue he is dealing with is the same as mine. Oil pressure is normally sits at a steady 40psi at idle and runs around 80 when rpms are up. However, occasionally the guage moves all over the place from 5 to 45 lbs at idle. This is something to do with the guage or sender and was hoping to better understand if replacing the sender fixed it or whether it may be a guage issue.

Understand that when they get tired the idle pressure can drop under 10 lbs when the bearing clearance gets excessive (built plenty of SBCs in my day) but my boat has less than 300hrs, no oil consumption, and 200psi compression in all cylinders so definitely not worn out.

Also it appears that they seem to be using a highflow/high pressure pump in the marinized version of this engine as typically pressure relief goes off at ~55 psi on std oil pump and most std pumps idle at 25psi when warm. Either that or the guage readings are off 20psi due to sender or guage...

j.mccreight@hotmail.com
06-27-2012, 11:04 PM
I think the issue he is dealing with is the same as mine. Oil pressure is normally sits at a steady 40psi at idle and runs around 80 when rpms are up. However, occasionally the guage moves all over the place from 5 to 45 lbs at idle. This is something to do with the guage or sender and was hoping to better understand if replacing the sender fixed it or whether it may be a guage issue.

Understand that when they get tired the idle pressure can drop under 10 lbs when the bearing clearance gets excessive (built plenty of SBCs in my day) but my boat has less than 300hrs, no oil consumption, and 200psi compression in all cylinders so definitely not worn out.

Also it appears that they seem to be using a highflow/high pressure pump in the marinized version of this engine as typically pressure relief goes off at ~55 psi on std oil pump and most std pumps idle at 25psi when warm. Either that or the guage readings are off 20psi due to sender or guage...

Sounds like its time to hook up a dvom and read the values at sender and gauge and compare those to a mechanical gauge reading.

Rossterman
06-30-2012, 12:58 AM
Sounds like its time to hook up a dvom and read the values at sender and gauge and compare those to a mechanical gauge reading.

Good point! Just came across a voltage/psi chart on barkers that shows what the guage should read at each voltage

Tom023
06-30-2012, 11:03 AM
If your boat uses and MDC with electronic gauges it could be the sender or the gauge. I had the same problem and swapped out the sender only to have the same readings. So, I hooked up an oil pressure gauge directly to the engine in the same port as the sender and had normal oil pressure readings at idle and under load at all RPMs. I'm sure mine is the gauge as the whole electronic gauge system in the early 2000's was problematic.