What is gonna be my benefit from doing this?
your benefit will be to find out if the engine heads/block/intake is cracked and where the cracks are if you can hear air escaping.
But since you didn't drain it then get ready to go shopping for another engine. Because what you described doing will not get the raw water out of the engine and its nearly a certainty the block, heads and intake are cracked.
This is why I always say, I feel every single inboard or I/O engine should be closed cooled with a heat exchanger. That way your engine is full of antifreeze like the car engine it really is, as designed by General Motors. It was the cheap fools at Mercrusier et al who came up with this lousy system of raw water cooling. Now there are literally thousands of boats with ruined engines all across the South because of this bad engineering practice. You forget JUST ONE TIME and it's done.
And this is why most people here are buying outboards even though they are very expensive. They have had I/Os and are done with the nonsense of scrambling to winterize them every fall. Because up here we know ONE TIME you forget and it's scrap iron!
The only way I'd have an inboard is with closed cooling. It costs more but so do new/reman engines!
