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Oil Pressure Fluctuating 5 to 55 when hot on port 454

knuckle47

Advanced Contributor
"Had a few recent issues with

"Had a few recent issues with carb backfiring that took 3 weekends to solve and seems to have been a cracked sparkplug. Motor runs beautifully but the oil pressure gauge is indicating low pressure after about 20-30 minutes of running. Motor does not smoke, heat up or tap (like my old 62 Ford back in 1981) The oil level is normal and IF I throttle back and run under 3000 RPM, within 10 minutes the oil pressure is back to 45 or so. Throttle up to 3400 or more and the pressure seems to sink back down to 15-20psi. At one point the pressue was about 5. Again motor does not overheat, or make any unusual sounds. I am guessing It could be a bad dual station sending unit. I did change the oil and noticed some sludge in the old oil on the bottom of the bucket so I flushed the crankcase out with new oil, ran it for 30 minutes and then sucked that out to re-fill AGAIN with new oil and filter after I saw this happening BUT...it is still happening. Can anyone provide another possibility beside the obvious oil pump, relief spring or filter problems? Is there something that can cause sporadic oil pressure shifts I am overlooking? These motors run very strong but had 600 hours. This season, we added about 150 more hours and I thought MAYBE we just stirred enough junk up to move the old solids around and have been getting it cleared out via these oil changes ?????"
 
"You need to test your oil pre

"You need to test your oil pressure with a mechanical gage, and right away!

Jeff"
 
"Al, what oil are you using?

"Al, what oil are you using? If you are using multi-viscosity try using straight 40. See if that makes a difference."
 
"I was using straight 40W and

"I was using straight 40W and with the other HEADACHES going on, added 15% LUCAS oil additive to bump up viscosity and add some extra protection ( I just love that little display at the parts counter where you turn the crank on those little gears) so, I changed oil several times. My last change while this pressure problem was developing was to switch BOTH engines to 10W-30 Mobil 1 extended performance. AGAIN, before doing that, I used the SEAFOAM in the carb and ran a pint thru the engines' crankcase to help cleanup any sludge there as well. After the SEAFOAM treatment, I ran 1 quick flush of NEW 10w-30 oil and filter to remove any other traces of CRUD left behind for about 30 minutes, AND THEN changed to the SYNTHETIC. The pressure problem had been occuring about 1 week before regardless.

While running out to the Mud Hole in NJ, the pressure dropped from a high of 60 on startup to a low of 20 while running at about 3200. We stopped the boat and CHANGED the oil filter and pressure came up to 6o on startup....After another hour, she dropped to about 20 again from its' usual 40-45 running pressure. Changed the filter again 20 miles out and went home between 3400 and idle ( no wake zones). I realized that after spending 10 minutes at idle, the 3000-3400 running oil pressure was right back at 40-45. Totally confused and believing that my engine is loosening up all this JUNK and clogging the filter, I have been changing the oil 4 times now since the problem developed. I did replace the dual station oil pressure sending unit yesterday but this is no real test yet until we are out running the boat. I did also pick up a mechanical oil pressure gauge as well. While I have no problem pulling the engine and bringing it home this winter, I REALLY REALLY would like to hope there is a better solution....Thank you all for the ongoing suggestions"
 
"Put the straight 40 back in.

"Put the straight 40 back in. If that doesn't solve it, and your operating temp is OK, you have other problems."
 
"OK Rick, NOW you've got

"OK Rick, NOW you've got me...What other problems do you think MIGHT be going on. My assesment is the oil pump. Beyond that I am getting lost. I can take the motor home, pull it apart, boil the block, measure all the clearances ane reassemble by the book, BUT the diagnosis part is what is getting to me. My Crusader manual has a few things to look for in the low oil pressure pages. I hope to systematically rule these out but once I get past item 2....it becomes a major job. I will drop the 40W in on Saturday and re-post the results....THANK YOU"
 
"Al, you are on the right trac

"Al, you are on the right track. If the oil is good and the temps are OK the only things that cause low oil pressure are not enough oil being supplied and not enough restriction in the pressure side of the system.

The pump, external lines, cooler and filter are responsible for the amount of oil being supplied. The bearings and clearances are responsible for the restriction. Lack of restriction will cause lack of pressure.

Don't put the cart ahead of the horse. Connect the mechanical gage before you do anything else. If the readings you see are accurate, change the oil (and filter)and run it again be sure to note engine temps. Inspect the external lines. They can delaminate and collapse internally, causing a blockage. Usually you will feel a soft area in the section of hose that has failed. Also, don't be afraid to remove and inspect the cooler. If you did pump as much gunk out of the crankcase as you claim, it is possible that some of it may have lodged in the cooler.

Let us know what you find.

Rick"
 
"Rick,

Quick question, The


"Rick,

Quick question, The u-cooler and raw water pump on this engine is new as well as the thermostat. I had a slight hotter running engine here at higher RPM's but normal Under 2500. By replacing those parts, it is back to normal again ON THAT PART.

Do you believe that the U-cooler can block up within the cooling sections for the oil so quickly( about 12 hours runtime)? The water passages are likley clean?

I absolutely will post any and all results. I have learned much by reading about everyone elses' stuff. Hopefully it will help someone somewhere ..AGAIN, ..... Thanks"
 
"No, actually I have never see

"No, actually I have never seen the oil side of a cooler clog, but I would still check it before I yanked the motor out. It is unlikely, based on the description of your problem, but still possible that some type of foreign matter has gotten in there, maybe the guts from an old filter or part of a failed hose."
 
"Hey! Stop believing in what

"Hey! Stop believing in what that electric oil pressure gage is saying and TEST with a mechanical gage. You might be chasing ghosts.
It's not uncommon for twin-engined boats with a flybridge to have FOUR oil pressure readings, all different!

Just imagine how dopey you'll feel if you yanked the motor, rebuilt it, and it did the same thing next year!

Jeff"
 
"The Mechanical gauge is insta

"The Mechanical gauge is installed but the weather is holding me back from running out this weekend....Hey, At least I would pretty it up a bit


You're so right, All the work doing that for something that dumb !!!!!"
 
"POSTING RESULTS: Played hook

"POSTING RESULTS: Played hooky to get some of this work done. Ran a quart of motor flush thru, changeed the oil and filter and then ran another oil change thru just to try and remove the motor flush as much as possible. Oil pressure mechanically is about 50psi running at the dock for about 25 minutes. NOT really any test there until I get it out on the water. Currently running straight 40W oil and a new K&N HP-3001 Filter. I have read that this filter has an anti-drain back feature to prevent the oil from rolling back into the engine.

Is it then safe to say that a conventional oil filter without this feature might allow filtered material to re-enter the motor when it is mounted horizontally?

I have also sent an oil sample to Blackstone Labs for a $20.00 oil analysis. I will keep you posted...."
 
"UPDATE: Headed out of marina

"UPDATE: Headed out of marina Sunday am and ran bout 30-40 minutes at 3400 or so. Oil pressure is a steady 40psi. After another 20 minutes the pressure dropped to about 25psi and stayed there all day fished, moved, fished, moved etc... After being anchored about 2 hours. Headed home with oil pressure aound 40, the after she warmed up, 20-25 minutes, she stood at 25psi all the way in.

Checked compression after we got in...125 average, no lower. Check oil levels, full & no smell of gas or milky look of water.

HERE IS THE FUN STUFF: The two hoses coming off the valve covers had a teaspoon sized blob of emulsified oil on the vanes of the flame arrestor. A perfect blend of water & oil that looks like tan mayonaise. The hoses shook out about 20 droplets of water and the walls lined with a thin coating of the MAYO... The white ceramic end of the spark plugs looks orange, NOT wet with fuel or soot, just stained orange. Which set of gaskets do you think could be leaking? If it helps, this motor runs 15 degrees hotter than the starboard STILL after a new U-cooler, raw water pump, thermostat and rod cleaning of the heat exchanger core. IT does NOT overheat. In fact, if the starboard is 160 so is the port but if the starboard is 140, port is 155. Hope this helps with any thoughts. Starboard engine runs textbook perfect...Oil 50 psi NO MATTER WHAT...temps 140-160 NO MATTER WHAT...flame arrestor...CLEAN as a whistle..."
 
"Our blocks are FWC. We suck u

"Our blocks are FWC. We suck up ocean water to cool the heat exchangers that circulate Anti-freeze coolant thru the blocks and then exhaust the hot air and warmer water back into the ocean along with a 3 to 15 foot trail of steam depending on the weather....... As I read it, the intake manifold can be removed without removing the exhaust manifolds and risers. While NOT insurmountable, it is 10X easier if I don't have to. Since this is a re-power from 350 cu.in. to 454 cu.in, the space on the outboard side of each engine is a bit limited."
 
"Al, There is no need to remo

"Al, There is no need to remove the exhaust manifolds. You can remove the intake without removing the exhaust, although you do need to remove the distributor. If you aren't familiar with reinstalling the dist., be sure to index it prior to removal and be sure not to crank the engine while it is out.

But... Before I took anything apart I would do a cooling system pressure test. If you can borrow a radiator tester it will allow you to pressurize the system and may well locate the leak without guessing."
 
"Thanks for the details, Rick.

"Thanks for the details, Rick. The distributor should not be a problem BUT, I never used a radiator tester before. How would it locate the leak other than to show a loss of pressure? Also, ( In case this means anything ) I poured in this cooling system cleaner by PENRAY called Nalclean 2001. It is supposed to help remove any sludge and rust in the cooling system. After Running for 3 weekends I have not seen the level in the recovery bottle change much other than for expansion . I also tried the U-TUBE fluid level test for head gasket leakage and it was negative. NO air bubble surges at any rpm.

I have the new head gaskets, intake manifold gaskets and even new grade 8 bolts to re-assemble the top end. I guess I can save the head gaskets for another time. (AGH!) Do you recommend any service to the intake manifold other than a good cleaning while it is off?"
 
"Al, If you're FWC and the

"Al, If you're FWC and the coolant level has not dropped, your intake gaskets are fine. In fact, there is no place else for water to get in to that system other than via the exhaust. There could be some water getting in the oil from a bad cooler but you just replaced that and that normally involves more than just a trace like you are finding. The water entering the intake through the vent hoses (the mayo you are finding) could explain the dry plugs. Water causes a lean condition in the engine, also causing higher temps. I might consider swapping coolers between engines and watching for a change. That's an easy swap and might reveal your problem.

Hey, if this was easy everybody would be doing it..."
 
"Hey, if this was easy everybo

"Hey, if this was easy everybody would be doing it...

Gee, That's a relief !
Just imagine everyone banging their head against a wall.
OK, assume I am wrong about the coolant level...Would the coolant level change need to be somewhat noticible? IS IT POSSIBLE to have the coolant level RISE within the recovery bucket rather than fall?

I just remembered that I do see a slight vapor coming from those valve cover hoses compared to the other engine when removed from the flame arrestor but still being fed from the valve covers. I hesitate to call it smoke but it is a visible puff which means it must have some particulate in it. When I mentioned the level did not drop, that would be in about 15 operating hours ...is that enough time to affect the coolant for a definitive call on the intake gaskets? Would the coolant pressure test add to this body of evidence? I might add under pressure of questioning, that the orange stains on the ceramic of the sparkplugs has a close resemblance to the stains on the waterline of boats in the marina against the white hulls. Kinda like that orange tobacco juice color. Also, could this water infiltration problem create the low oil pressure as well? My next step is to swap U-Coolers...

One more note to confuse things. The engine starts when cold IF you pump the throttle 2-3 times before cranking and then IF IT CATCHES (and it usually does with continued 7-10 seconds of cranking), you need to idle a bit higher like 12 to 1400 to keep it running until it warms a bit. The other engine starts as if it was fuel injected. I do not have the electric chokes wired in on either one. Whew, I think I'm getting dizzy

I apologize for rambling..Maybe, I'm getting desperate for a solution or direction, I heard the possibility of snow next week ..."
 
"OIL ANALYSIS RESULTS: Blacks

"OIL ANALYSIS RESULTS: Blackstone Labs called today about the oil sample. I do not yet have the emailed result so exact details remain unknown but the conversation on the phone was that there is more than 5% coolant found in the crankcase oil and 3.8% solubles in the oil. Obviously a problem...Looks like the motor is coming out this winter, anyone have a comment ?"
 
"WELL, I received the email ab

"WELL, I received the email about the oil sample and the coolant that has been getting into the crankcase has apparantly been creating the sludge that has been clogging the oil filter. This in turn, has been adding loads of sodium,calcium, magnesium and silicon to the oil in significant quantities as it solidifies under the high temps the coolant is exposed to. Likely a head gasket so The block will be removed and torn down this winter.

THANK YOU EVERYONE who has helped with suggestions along the way. I KNOW I will have many more questions as the winter rebuild goes on..."
 
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