4bus

iTrader: (4)

Strangely enough my 575sci's use zero oil, I have never had a boat engine not use or leak just a little. I keep checking and checking, but stick always shows full. 40 hrs total now, wonder what the major difference in this 502 based engine that it doesn't use oil?

I run Valvoline full syn off road high zinc 25w50 racing oil, and one bottle of Valvoline moly/zddp additive for my flat tappet cam.

PA.WOODCHUCK

I looking at a just under 1997 boat w/502 MPI Magnum and owner stated 1 qt per 10-12 hours. That said, was is the cause(s) of this issue? What is the factory weight oil used, oil capacity, and what are suggestions to reduce the consumption if possible?

Another subject does this engine have big port heads, forged rotating parts? Please add to this as I been outboards for the past 25yrs running cat boats and need to slow down per my doctor.

thanks

1MOSES1

SB

iTrader: (1)

5qt jug of Mobil 1 15-50 is $22.88 at Walmart. Pretty hard to beat. Worth a shot OP. Nothing to lose as it is very good oil anyway.
https://www.walmart.com/ip/Mobil-1-1...5-qts/20713647

PA.WOODCHUCK

Spec on compression per manual is 150 at sea-level. Lowest cylinder is 130 and all others are 140+ about 800ft elevation. That's per present owner I'm buying boat from and will do my own with my Snap-on gauge. Engine just under 500hrs and STOCK.

Isn't "50" oil a bit too thick when mercury spec 25-40?

SB

iTrader: (1)

No. 15/50 - 20W-50 is all good.
Straight 50 would be a little too thick. LOL.

BTW:
Steel Forged crank
7/16" bolt GM Rods
J&E Forged Pistons. Low Tension oil ring
GM 502 block. These have 4 bolt mains and blind (do not go into water jackets) tapped head bolt bosses.
Rectangular Port Cylinder heads.
Extremely mild low lift cams - thus most of these engines will go tons of hours without needing rebuilds. 410hp is very mild for a 502.

cigrocket

iTrader: (3)

I would say a quart every 10-12 hours depending on how hard the boat is run is pretty good for the 502. They always used oil.

I like running Valvoline high zinc 25w50 racing oil VR1 conventional oil in all of my boat applications. Have had great success... Also K&N Oil Filters

Gimme Fuel

I removed the PCV breather system on my 502mpi that have 1000 hours on them. Was using half quart a weekend. After removing the PCV and going to a catch-can breather, I didn't hardly even use 1/2 quart the whole season. No oil wound up in breather cans either. 20-50 Napa brand oil with 1 qt. Lucas stabilizer too.