my '97 500HP is getting small amount of water in oil. Just had top end refreshed and new head gaskets, pressure test block, pressure test manifolds, etc. All looks good. Started engine on boot and let idle for bout 5 mins, then took riser off of manifold (Gil Marine-stock small riser and about 15" to the end of tailpipe where water exahust mix) and it was wet inside manifold and the riser had water droplets at elbow. If i'm correct, there should be no water at the elbow and especially in manifold, so I'm thinking this may be water reversion. So I think that may be where the water is getting mixed with oil. With that being said, what do I do now?????????? Find a taller riser and longer tailpipe or go dry?? Or is this my problem......??? Please HELP

if you did not have this problem before [reversion] you should not have it now,did you change the cam or timing chain?did you use the right head gasgets?gen 4 gasgets on gen 5 or 6 will leak.post more info on what was done&what parts were used,then we can figure out whats wrong.

sounds like your getting reversion but it wouldn't get the oil milky after 5 minutes of running...did you seal the head bolts and use sealer around the intake's water passages?

i would look for a set of dry risers or have yours extended..

You could try switching your risers and see if the problem moves to the other side. you can also try letting it run at say 1000-1200rpm. If it stays dry inside the manifold at the higher rpm, then you have a reversion issue. Low idle speeds is when reversion is a issue. But if you didnt change cams, i dont see why it would be a issue now, and not before.

I would think you have a leaky riser, esp if they are older and used in salt.

no cam or timing chain. the timing was off and had to be set, but they used head gasket for the engine as specified, just had new springs installed. I didnt have any water/oil mix previously, and pressure tests have been done on block and on manifolds and they test good. and since there is no way to pressure test a riser/tailpipe, we still took them off and ran water in them and it no leak....SO How could water/moisture get into the manifold then to engine oil??

This might be a long shot, but if the valves were not adjusted properly when they put it all back together, and you have a exhaust valve hanging open, this can suck water back into the cylinder.

If you have a compression tester or leakdown tester, it might be a good idea to check the cylinders on the side of the motor where the manifold was wet....

Make sure the boat is sitting on a slight slope with the stern lower, like it would be at idle in the water.

What method did you use to pressure test the manifold?

Just pump up air pressure at 20psi. and the manifold was still on engine!

You might want to put the manifolds on a garden hose. Hook a hose up to one end and turn on the water to push out the air and fill with water. Once you see water come out turn the hose off then plug the other end. Turn the water back on and hope for the best.......