Spins bearings.....are you using the right bearings?

i disagree,leaking exhaust valves can cause the cylinder to revert enough water to milk the oil.

After you mention that, he did say he's leaking at about 40%. That could be highly probable then.

its probably more likely you have a cracked water jacket.

Im in west Chester pa. The mk4 ran its ass off just kept eating bearings. But if they aren't the right heads I won't bother switching them over

Are you trying to get thru this season, or looking into what you need for this winter's build? Was mk4 dished or flat pistons? Is this a mag motor? Or a gen 6 that has mag heads on it? And is it still in the boat? Also, what is the boat and how is it run? A lot of people push it to WOT for a few seconds each trip out and spend the day at 3500 to 4k. If that is the case, the ovals are just fine for you. And the alum rectangle mag intake will fit and run just fine on the oval heads.

the boat is a 24 checkmate enforcer. I probably run between 4K-WOT which maybe that's why I keep spinning bearings. The mk4 is in the boat but sounds like it's starting to knock and at this point I figured I would start over with an entirely different engine which is how I came across this mag motor. It's definitely a mag and I ran it on the ground and it runs rough and oil got milky so I did leak down. I was hoping to use heads from mk4 and make one good engine out of the 2 but I didn't realize they were oval heads and at that point the mk4 is a flat tappet cam so I assume to put the heads on the mag I would have to change the valve springs be cause it's a roller. Sounds like too much work and I should just address the mag motor and see what all it needs. Not sure what pistons are in the mk4

No.

No, you could run the ovals on the mag just fine. Chambers essentially identical. No piston to head clearance issues. Valves, springs will run on the oe roller lifters. You would have to run the newer pushrods so if pushrod dia are different you will need 3/8 guideplates to fit the 7/16 rocker studs. I have at least one set here. Gen 6 no fuel pump mount. Did the mag come with the water pump-fuel pump combo? Otherwise an electronic fuel pump is necessary. The one pain is if using all the mk 4 brackets, the gen 6 are 7/16 instead of 3/8 and drilling that little bit bigger is no fun. But most attach to the heads, not the block so less holes to adapt. You could have that gen 6-oval beastie together in a couple evenings. You will want to drop the pan and check the rods and mains. I bought 2 different supposedly good engines and found bad bearings after installing the engines.

The mag motor came fully dressed. All accessories fuel pump fuel injection computer everything. If the intake manifold looks ok do you think I should stick with the fuel injection with these other heads or swap the intake carb and everything from the mk4?