MWalsh831

Hey guys I'm replacing the screen on my oil pump because I'm convinced that it is built up with sludge and losing pressure after about 20 minutes. I figured while it is out I might as well replace the pump since I am there. The guys at the local boat shop said to not use a High pressure/volume pump, but to use a Heavy Duty (never heard of one). I can't find a heavy duty pump for the 454. So I called the guy who has done some motor work for me in the past and he suggested a M77HV which is a high volume standard pressure pump.
Any input would be great.
Don't know if it matters but it is in a 89 IMP Eleganza 310

FIXX

iTrader: (2)

melling,,10778c its worth the extra 30 bucks..make sure you replace the pick up tube also and it needs to be tack welded on so it dont fall off while pounding waves..

MWalsh831

I guess another question I have is with the high volume (these list at 25% over stock) I wont have an issue with the stock pan? Some people say you need at least a 12 quart pan (which seems like a little much). I like the idea of that anti-cavitation pump and I get a good deal on parts, I'll probably spring for that as long as there is no issues running the stock pan with a HV pump.

f_inscreenname

Stock pan, big oil cooler, holds steady at 70psi

cubicinches

What exactly is leading you to believe the screen is built up with sludge? And, if that's the case, why would the engine take 20 minutes to lose oil pressure?

How much oil pressure does it lose?

To answer your original question, I wouldn't bother with a HV pump in a stock pan. If the engine is stock, there's nothing to be gained by using a HV pump.

FIXX

iTrader: (2)

use the pump number i gave you,,if it comes with another spring read the directiond and it will give you lower pressure so you dont suck the oil pan dry.

picklenjim

Oil pressure will always drop some from when it's cold to when it gets hot. Seriously doubt there is any sludge what so ever on the pick up screen. HV pump is totally unnecessary on a stock engine. All it will do is use more power from the engine to turn it.

stevesxm

some good thoughts posted above about your analysis ... " why 20 minutes ?" and " loses press cold to hot " and i think you need to look around a bit before you jump to conclusions and have to do a lot of work again...

first thing to ask and report is how it used to be... is this a new problem, sudden problem, never did it before, always did it before , oile temps bef and now etc... those answers tell you a lot about what's really happening... but beyond that even, what are the critical numbers ? cold idle, hot idle , cold 3500 rpm, hot 3500 rpm.

lets assume that you have a real issue... press used to be normal, now they aren't and temps are ok... you think you have sludge... well that's unlikely but its as good a guess as any and assuming you have done all the normal external things first, lets say you have the pan off... what do you find ? is there an inch of sludge in the bottom of the pan ? well ... if there IS then you need to seriously consider having a look at the rod and main bearings while you are there for obvious reasons... and the top end of that motor isn't going to be a joy to look at either ...( and how did you let it get like that ?)

as for oil pumps... don't reinvent the wheel. the oil pump and specs that it came with did the job just fine for a long time and was designed for the clearences and bleed rate that your motor has. hi vol oil pumps and all the rest aren't cures for anything that isn't broken and since you aren't changing the basic archetecture of your motor , you don't have anything to fix in that regard. put stock specification right back in.

and someone please explain to me this whole " suck the pan dry" routine... where do you think the oil goes and hides ? it comes out of the pan, thru the pump, into the galleries, thru the bearings and back into the pan... if its too much it bypasses ... into the pan.

there is nowhere to hide 500 cubic inshes of oil unless every drain back from the top end is sludged solid as well... and if thats the case then no band aid oil pump or oil pan is going to fix any of this...

apollard

All good questions raised, and I'll add one more - loosing pressure after 20 minutes of running could be an oil cooler problem. The stock oil cooler is sized for nothing more than a stock engine - adding power, etc will overheat the oil. On mine, the PO put in a 160* water t-stat, and I was seeing oil pressure drop after 5 minutes of WOT. Check of oil temp showed it was reaching 280* oil temp. Changed to the specified 140* t-stat, and problem solved. I'd check all the folks above pointed plus the cooler function and water temp before changing anything.

MWalsh831

I run a 160 t-stat which is what the MPI calls for. Its a 89 block with 300 hours, and I put a fresh set of '98 heads on it with a Merc MPI setup.
before I bought it the motor sat for 2+ years with used oil so I'm thinking that it clogged the pickup enough to supply sufficient flow at lower RPM's and for short periods of time at higher RPMS.
I had the oil cooler pressure checked before the engine was installed and was told it was alright.
cold idle psi is about 30, 1k is about 40.
I can run it all day at 3k and have it hold 30psi + or - a little. Its when I run it to WOT that it spikes at about 45 and starts to drop slowly after about 10 minutes. If it's the mains and rods then I waste a day of my time pulling the motor and replacing a 70$ melling pump. My season only has about 6-8 weeks left I'll see what happens.