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Low Oil Pressure on Rebuilt 454

Old 07-05-2011, 08:40 PM
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Default Low Oil Pressure on Rebuilt 454

I recently just purchased a PowerQuest 260 Legend SX with a rebuilt 454MAG with a Vortech Supercharger. Roughly 20 hours on the engine now. When I first start the engine up oil pressure isnt too bad but not the greatest at about 36-39psi. It will stay in that same range at idling speed in no wake zones and even stay there when I get up on plane and all thru the RPM band. When I get off plane and go back to idle is when I really get nervous....drops to somewhere between 10-20psi!! After again idling in no wake zone the pressure we steadily climb back up to the 36-39psi range. I really hope it's nothing internally in the engine.... What are some recommendations on starting to pin point my problem? I would rather obviously check EVERY external factor that I can before I pull engine! Not an engine expert my any means but I'm throwing this out there...can it be a bad oil pressure sender? Engine is not running hot and runs real cool, I hear no crazy noises. I did add about a half a court of oil and is no topped off and seems to not be losing any, but I will check again to make sure! Gotta love buying a new boat.......
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Old 07-05-2011, 08:52 PM
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Its absolutely normal for an engine to drop 20-30lbs of oil pressure after running at a cruise speed or harder and then dropping to idle. I would change your break-in oil and put a good quality straight 40 Wt or a 20-50wt racing oil and I'll bet your pressure rises. Good luck
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Old 07-05-2011, 09:12 PM
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That was my first choice to do was to change the oil. The previous owner said he did change the oil once since rebuild but I can imagine it needs it again. I have looked at the oil on dipstick a few times and seems to be not too bad. I'll let you know the results from changing the oil. Thanks for your help guys!
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Old 07-05-2011, 09:45 PM
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Originally Posted by ACE7WILD
That was my first choice to do was to change the oil. The previous owner said he did change the oil once since rebuild but I can imagine it needs it again. I have looked at the oil on dipstick a few times and seems to be not too bad. I'll let you know the results from changing the oil. Thanks for your help guys!
first i would definitely change your oil and put a heavy duty oil in there like a 15-40 or a 20-50 or straight 30wt in there. my builder recommended a breakin oil and then run straight 30 after about 5-10hrs, so i'm taking his advice. i build about 70psi idle cold, and then after warmup run about 50 idle, then after a hard run about 35-40 idle. it'll climb about 10-20 above idle numbers as i rev up depending on my temps. usually a good rule of thumb is 10psi per 1000 rpm's and you're safe. can't hurt to change the oil and make sure you have a good oil in there. you wouldn't believe the difference it makes with the right viscosity, and you never know what the previous owner decided (in his infinite wisdom) to put in it.

second i would buy a cheap sunpro oil pressure gauge from autozone and stick that on there to insure your dash gauge is right. they're less than $20 for a cheapie.

Last edited by hondahp4; 07-05-2011 at 09:48 PM.
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Old 07-05-2011, 11:14 PM
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You may want to consider an oil temp gauge - the extra load from the supercharger may be causing the oil to get too hot, hence the low readings. Was the oil cooler upgraded to a larger size when the supercharger was added? Why was the engine rebuilt? Was the supercharger on there before the rebuild? It's possible that he wiped a bearing due to oil breaking down from the heat. Don't mean to alarm you, but there are a lot of threads about that on here.

FWIW, a friend just bought a boat with a stock 454 Mag MPI in it with 285 hours on it. We ran it last week on fresh Merc oil, and it would only show about 40 PSI while running, and dropped all the way down to 20 PSI at idle. I did a search for him on OSO, and turned up a lot of threads that showed that this is fairly normal for a stock engine. It set his mind at ease. However, with a supercharger you are in a whole different league. I would be more comfortable with higher pressures with any amount of boost on the engine. The bearings take a beating with loads like that.
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Old 07-06-2011, 08:38 AM
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as I mentioned oil change first and see if that helps any.

I might as well try out the $20 Sunpro AZ special gauge to make sure gauge is functioning correct while I'm at it.

No I don't believe the oil cooler was upgraded after supercharger was put on and was eventually planning on putting an upgraded one in. Anyone have a recommendation on which oil cooler I should put on?

Supercharger was on engine when previous owner had water lock last year, which is the reason for the rebuild.

The supercharger is only putting just shy of 3 pounds of boost which I would like to think is a "mild" number?

I know the supercharger puts me into a different category but most of the time I run it in VAC rather that BOOST. Not a big fan of blowing up the engine and would like to make it last!!
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Old 07-06-2011, 09:02 AM
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Another friend of mine has an HP500 with a ProCharger on it. He had his engine rebuilt last year, and it was running low oil pressure as well. It turns out that his builder had used the factory standard volume pump (apparently Merc does not put the high volume pumps in from the factory) with the lower pressure spring. He pulled the engine and pan, and started with just installing the heavier spring in the LV pump. He spun the pump with a drill at about 800 RPM (equivalent to about 1600 crank RPM) and went from about 30 PSI up to nearly 60 just with this change. He probably would have been fine with the LV pump and heavier spring, but he opted for the HV pump instead, just in case.

Can you get in touch with the engine builder to see what part number he used for the oil pump? It might be as simple as changing the spring in the pump. Of course, that would mean pulling the engine, and no one looks forward to that. You might be able to baby it through the season and pull it out over the winter.

I guess the mechanical gauge will tell the tale.
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Old 07-06-2011, 12:16 PM
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budman makes a good point with oil temps. that would be something else to look into. that charger could be making enough heat to toast some oil and cause viscosity breakdown.

listen to budman, he knows his stuff. he helped me with a bunch of my own issues, including some oil pressure issues. mine ended up being a clogged up oil pickup in the pan. what happened was the previous owner rebuilt the motor and ran it. then it sat for a year or two and was never started. it seems the assembly lube was washed out of the motor, and then settled out of the oil as it sat for so long. well after running it the first time, the pickup sucked up all the assembly lube off the bottom of the tank, and clogged the pickup. budman's suggestions were a great troubleshooting tutorial. hopefully your issues aren't as severe as mine, but i ended up pulling the motor and rebuilding it (bearings worn from low pressure). good luck, try the cheap stuff first, but as we all know too well, usually boat problems end up being expensive
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Old 07-06-2011, 04:00 PM
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what budman says is true, these engines stock don't run a lot of oil pressure...but a properly set up big block chevy does not need a bunch either...the stock oil lines, cooler, filter mount and block releif valve are junk and should all be changed..some good info here on that...I just finished mine...new block adapter, #10 lines, big cooler, new filter, 30 psi valve in block...
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Old 07-07-2011, 09:43 AM
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thanks for the input guys! gotta love OSO as the input received is 10x better than you can get from any one mechanic!!

ezstriper - as far as those items you mentioned you just installed, what brand, model, etc do you recommend to go with for each? I would like to get some parts ordered so I can call my engine mechanic to setup an install date. This may be a dumb question, but the engine doesn't need to be pulled for installing these items does it?
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