Low oil pressure at 4000 RPM ???????
01-05-2012, 06:47 PM
#41
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I will describe the best I can.
At idle, cold (1000 rpm) the pressure will run about 70psi. By the time I get out of the marina, and into the main channel, at idle, the oil has warmed a bit and the O.P. settles in around 60 psi. I have about 3 milles of no wake, so by the time I can open it up, the oil is pretty much at temp, holding 60psi. I can plane out and run sub 4000 RPM, and the pressure will remain 55 - 60 psi and oil temps around 210 F. I have run for over 30 miles under 4000 RPM, and the OP remains steady at 55PSI. Push the RPM up past 4000, say 4300, and the oil pressure will start to drop to about 20 PSI within 2 min of RPM increase. The pressure will remain there even if RPM is increased (have run it up to about 5200). Some slight fluttering (1 - 2 psi) will occur at higher RPM. The oil temp will rise, but only about 10 degrees. If you bring her back down to 3500 RPM, the pressure will build back to about 50 PSI within 2 - 3 minutes. You can bring her back up to 4300, and the same sequence willl repeat.
Due to location, and the no wake zone, I have never been able to run it hard when the engine is not warmed to temp.
At idle, cold (1000 rpm) the pressure will run about 70psi. By the time I get out of the marina, and into the main channel, at idle, the oil has warmed a bit and the O.P. settles in around 60 psi. I have about 3 milles of no wake, so by the time I can open it up, the oil is pretty much at temp, holding 60psi. I can plane out and run sub 4000 RPM, and the pressure will remain 55 - 60 psi and oil temps around 210 F. I have run for over 30 miles under 4000 RPM, and the OP remains steady at 55PSI. Push the RPM up past 4000, say 4300, and the oil pressure will start to drop to about 20 PSI within 2 min of RPM increase. The pressure will remain there even if RPM is increased (have run it up to about 5200). Some slight fluttering (1 - 2 psi) will occur at higher RPM. The oil temp will rise, but only about 10 degrees. If you bring her back down to 3500 RPM, the pressure will build back to about 50 PSI within 2 - 3 minutes. You can bring her back up to 4300, and the same sequence willl repeat.
Due to location, and the no wake zone, I have never been able to run it hard when the engine is not warmed to temp.
01-06-2012, 07:52 AM
#42
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How can I tell.
I am using the MERC racing cooler and stat from the old hp500's. I am not really familiar with what is going on inside that black box. I routed the lines the same on both engines from engine adapter to t-stat / filter block, then to oil cooler.
To me, it does seem like something shuts the oil flow off. That would explain the wear on the dist gear.
Whatever it is, reduces the oil pressure accross the engine, by that I mean I have taken oil pressure readings from multiple taps in the block, and all follow the same pattern.
I am using the MERC racing cooler and stat from the old hp500's. I am not really familiar with what is going on inside that black box. I routed the lines the same on both engines from engine adapter to t-stat / filter block, then to oil cooler.
To me, it does seem like something shuts the oil flow off. That would explain the wear on the dist gear.
Whatever it is, reduces the oil pressure accross the engine, by that I mean I have taken oil pressure readings from multiple taps in the block, and all follow the same pattern.
01-06-2012, 08:50 AM
#43
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How can I tell.
I am using the MERC racing cooler and stat from the old hp500's. I am not really familiar with what is going on inside that black box. I routed the lines the same on both engines from engine adapter to t-stat / filter block, then to oil cooler.
To me, it does seem like something shuts the oil flow off. That would explain the wear on the dist gear.
Whatever it is, reduces the oil pressure accross the engine, by that I mean I have taken oil pressure readings from multiple taps in the block, and all follow the same pattern.
I am using the MERC racing cooler and stat from the old hp500's. I am not really familiar with what is going on inside that black box. I routed the lines the same on both engines from engine adapter to t-stat / filter block, then to oil cooler.
To me, it does seem like something shuts the oil flow off. That would explain the wear on the dist gear.
Whatever it is, reduces the oil pressure accross the engine, by that I mean I have taken oil pressure readings from multiple taps in the block, and all follow the same pattern.
01-09-2012, 09:07 AM
#44
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I completely disassembled the engine. All oil passages in the block are clear. Clearance in the mains is at .0030" accross the board. O-ring was in place under the rear main cap. All bearings look good. The only two dd things I found was the excessive side clearance on the rods, .0290" to .0320", and I also found the disk on the oil T-stat was not seated, it was cocked a bit, and not fully seated. Could it be that when the T-stat opened, it plugged the oil passage ? This would cause the oil bypass valves to open, and maybe restrict the oil flow ???
Still no concrete answers.
Still no concrete answers.
01-09-2012, 09:25 AM
#45
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I completely disassembled the engine. All oil passages in the block are clear. Clearance in the mains is at .0030" accross the board. O-ring was in place under the rear main cap. All bearings look good. The only two dd things I found was the excessive side clearance on the rods, .0290" to .0320", and I also found the disk on the oil T-stat was not seated, it was cocked a bit, and not fully seated. Could it be that when the T-stat opened, it plugged the oil passage ? This would cause the oil bypass valves to open, and maybe restrict the oil flow ???
Still no concrete answers.
Still no concrete answers.
01-09-2012, 09:44 AM
#46
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Also if you have a good drill that can run your pump over 2000 rpm, you can simulate your situation without running the motor. It would be one way to isolate the problem. I have run into a few problems like this before, one was the oil pump pressure relief stuck open, the other was an internal blockage. I think you need to look at things that are affected by increased volume. It appears that as volume increases due to increased rpm the problem occurs. it's also interesting that the problem reacts so slowly. Based on the gear wear, I would concentrate your efforts on everything after the pump. It appears to be a pressure side issue. I would definitely cut the filter open and look for any structural incongruities. Typically if there were a hose problem that caused this magnitude of change there would be a leak.
01-30-2012, 08:02 AM
#48
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So far I have not found any positive answers. I did get a reccomendation to tighten up the side clearance on the con rods, so I am ordering a new set of rods. I stripped all of the plugs out of the bllock, and flushed every oil passage. They were all clear. I am going to replace the oil pump, and close up the bearing clearance slightly (.0025" - .0028") currently .0030" - .0032". Even though they look good as is, I will be replacing the cam bearings for good measure. I am installing a FAST EZ EFI system, so I am going to try and rent dyno time at a local shop. That should give me a heads up if there are any issues once it is back together. I always have my tired 500's sitting on the shelf as backup.
