One argument is cooler oil temperatures (which I call bs).

The major benefit is keeping the oil pump bathed in a constant supply of oil, the heads and lifter valley can hold large amounts of oil, especially without good windage and ventilation control in the crankcase.

99 times out of 100, a ten quart pan is enough. Something I always say is that a ten quart pan does not really hold ten quarts. Same can be said about a 12, a 14' and so on.

The other things to take into consideration is the room they take up and service access.

We ran a 14 quart pan and an Oberg filter on the race boat with a bypass system to filter the oil down real tight. The system worked perfect, but it was a ton of money in oil capacity.

We could have easily gotten away with a ten quart pan, but we would have had to change the oil more often (the added oil stays very clean, much longer). This was a marathon engine that ran 80-120 miles a day for two or three days. Absolutely wide open.

So to each their own, if you are only talking a couple quarts, it's not a really huge debate. Just make sure the trap doors open extremely easy and the pan is stupid clean when you install it.

You can use a measuring cup and water to see what the capacity is....... Should be just below the tray when full.

GT

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Inquiring minds want to know; and one test is worth 1,000 theories.

I have this oil pan of unknown origin that I decided to run some tests with.  This is off of my boat and it's probably what will go back on, after some minor modifications.  Anyway, it's chrome, so it must be good, right?

I also measured the stringers on a 19' CP.  I zeroed a digital level on the keel, just in front of the intake.  This is the location where all of our measurements are basselined from.  The suction surface of the intake is 4-degrees up towards the bow.  The back cut of the shoe is 3-degrees down towards the transom.  The ride plate will initially be set 4-degrees up towards the diverter.  The nozzle will initially have 7-degrees up and 4-degrees down nozzle.  These are just starting points and may change as the combination is fine tuned.  I am including these numbers to reinforce this location as baseline for all other measurements.

So, here are my findings:


The stringers angle up 0.6-degrees towards the bow (Picture 1).

The engine angles up 2.5-degrees towards the bow, relative to the stringers.  That places the engine (in this boat) at 3.1-degrees angled up towards the bow, relative to the keel.

The oil pan:

I started by rigging the pan at 4-degrees up (Picture 2).  Filled with 10 quarts of water, the level is 1/8" below the top edge of the rear baffle (Picture 3).

Dropping the front of the pan down to 2-degrees, the level is 1/2" below the baffle (Picture 4).

Filling the pan with a total of 11 quarts, while at 2-degrees, the level returned to 1/8" below the rear baffle.

With the pan level, 12 quarts brings the level within 1/8" of the bottom of the windage tray (Picture 5).

Conclusion:

I still have no idea what the relationship between the engine and the surface of the water is, while on plane.  A guesstimation, the engine could be over 8-degrees angling up towards the bow, while on plane (in calm water).

With just 4-degrees of angularity, 10 quarts comes dangerously close to the rotating assembly.  Any more angularity or quarts and the crank is beating the oil into froth.  Picture 6 illustrates what 12 quarts @ 8-degrees looks like, putting the oil level just 3/4" from the oil pan gasket and well into the 4th crank throw.

This should also illustrate, just how important a rear pan baffle is.  Granted, the oil pump takes up a lot of space where the windage tray is cut away, the pump does not seal to the pan, nor does it prevent hot oil from flowing around it, into the spinning crankshaft, and up into the 7 and 8 cylinders.

Lastly, deeper is better because the oil level is further away from the rotating assembly.  Unfortunately, 8" deep is what we are limited to.  Picture 7 shows damage from the intake bolts.  Moving the engine forward can allow a slightly deeper pan.  Raising the engine is not worth the increase in center of gravity.

What are the benefits of a larger capacity pan...I have a 12 qt. pan...which I would like to trade for a 10...Is there any good reason that i should just run the larger capacity pan?

Given a choice between a 10-qt pan & 12-qt pan, I would opt to run the pan that will provide the best oil control for the engine.  The difference in capacity in this case probably doesn't matter at all