I need some help. Boats down in storage so I need a plan before going to get it.
2003 525efi with around 300 hours. fresh water only. a coup[le weeks ago it started missing and dropped a couple cylinders. Discovered that head gasket was blown in between cylinders on one side. Pulled that head and changed head gasket. Put back together and topped off antifreeze and ran for about 2 miles and raised hatch to check and had milkshake coming out of blow by hose. Resvoir was empty. Topped off again and ran again and same thing only the milkshake came up into valve covers. The antifreeze/water for the closed cooling is going straight into the oil. Need ideas of what to check first or any ideas.

The oil and coolant in closed systems never cross paths......

However, the OIL cooler at the rear of the engine seems suspect. Otherwise, you need to look at the other head too.....

Are you sure you used the correct head gasket?

Probably intake gaskets. Also, A lot of 525's run into cracked headers too right ? Psi test heat exchanger and headers.

Why did the fire ring disappear ? Biggest reason I see is overheat condition. 2nd is too much nitrous and not enough fuel. Ooops. Forget the last one. Lol. But, same deal NA where not enough fuel and shazaam...lucky it does this vs eat a piston and/or ring. But, when I fire ring disappears between cylinders a lot of times the surface of the head and/or block get's 'notched' in the same exact spot.

Was block/head checked for this and straigtness ?

Again, was root cause found for why headgasket went ?

If it torched the head gasket between the cylinders, you can almost be assured that it has eaten away the head and/or block. One or both may need to be surfaced.
Eddie

A leakdown test may reveal the problem - air leaking into the water jackets indicates head gasket. You could also set up a jig to pressure test the cooling system by blocking off the circ pump and t-stat flange and installing a schrader valve. If you are lucky it is just an intake gasket leak.

Also, hate to be the bearer of bad news, but depending on the type, antifreeze can attack bearings. Not sure what type is run in a closed cooling system. That is probably the only advantage of raw water cooling - water mixed in oil is less damaging to bearings than antifreeze.

head and block was checked.

With what.

My 4th graders ruler