Oil Pressure
 

I was watching videos of my boat running. I currently have 60hours on my 525sc (468/572hp) motor. No issues at all. I have a new livorsi electric oil pressure gauge and sender, verified with a mechanical gauge. I have a Melling M77HV pump. I have a hot idle pressure of 20-22psi, at 3500 its at 50psi, at 4500 its still 50psi. The engine runs perfect. Would you pull the motor to swap to a 10778 pump?

i would have started with a 10778 because it is a better pump but to answer you,r question,i would not pull the engine now as it will be fine the way it is.what wt and brand of oil are you using?

Brad Penn 20/50 with a K and N 3002 filter.

Oil https://www.summitracing.com/parts/b...7119/overview/

Nothing wrong with those pressures at all...

^^^^^i agree,you will be fine.^^^^^^^^^^^

Cut the oil filter open look at it and if its clean put new filter on and have a nice day.

Seems like I should leave it alone. It either gets idled for 10 min out of the marina or run 4000-5000 rpm, not much in between. I am kinda hoping with 60 hours on it, I am in the clear.

I am running this https://www.summitracing.com/parts/sme-2015 bypass eliminator on the block with this spin on adapter. https://www.summitracing.com/parts/trd-1050
if you look, the left hole on the spin on adapter does not line up with the center hole. I wonder if switching adapter setups would help. maybe to this? https://www.summitracing.com/parts/ctr-22-592/overview/

the standard spring in the M77 pump, is set to internally bypass at 52psi.
Purple spring = 52psi
Black=60psi
pink=70psi.

It didn't come with any other springs. The 52spring would make sense.

What do the 10778 pumps bypass at?

That's a guess I never had one that would not make around 60psi hot.. Around 5k with good bearing clearance.

Just curious, is your filter pad that hard to get to that you have to use a remote filter mount? I would get rid of that spin on adapter and put that K&N right on the block. Or do you have a cooler plumbed in there also?

Where are you taking your pressure reading?

What size oil lines going to the cooler and back to block?

Years back, my engines would max out at 50psi oil psi when up and running warmed up..would actually drop from 50 to about 45 above 5000rpm. Previous owner had rigged the oil system, full of hard 90* brass fittings, a canton screen type canister filter, then to a standard remote filter -8 lines, it was a mess of plumbing. Got rid of all that, ran -12 lines from block to cooler and back to block, mike tkach shimmed the pump bypass spring, and have 75-80psi up and running hot.

Icdedppl had similar issues. He was getting like 70-80psi reading at his filter head. But at the main galley oil plug, he was getting about 15-20psi less than that . Previous owner had ran -12 lines from block to filter, then -10 lines from filter to cooler and back to filter. He replaced them with -12 , and voila, no longer had the pressure loss at the main oil galley.

The pump is going to bypass based on the psi the pump sees. The pressure the pump sees, may not always be , the psi your gauge sees.

All BBC Merc I/O's have a remote oil cooler.

Try a different filter, seen 10-15 psi diff I use a NAPA gold

Joe, I bought a stock Merc 500hp carb oiling setup. I got the cooler, non-thermostatic filter housing, and all lines off a buddy's 500hp when he upgraded. I didn't use the block adapter as his was GEN5, mine is mark4.

I have the pressure sending unit in the block and the oil temp sending unit in the filter head. The hoses and block adapter all have 1/2"npt. The hose seems to be the same diameter as 1/2" npt fittings, however the fittings on the cooler are 90* and slightly smaller. I assumed it would all be fine since its all stock 525sc/500hp stuff.

I don't know if it matters. I have the oil going though the cooler then the filter. Maybe the pressure drop would be less if the hot oil went through the filter then the cooler. That way the thinner hot oil would go through the filter easier than cooled oil. My oil temp is just a touch under 140 at cruise and 150 WOT.

I have the same cooler and lines as this engine. My filter is non-thermostatic.

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