Ok so merc does not have a diffinitive answer considering I don't have a stock. Hp500. Stopped by the engine shop that did the work and he recommended a leak down and that maybe engine block deck might not be straight. I don't have a leak down tester so I was thinking of just doing a compression test on the engine stand to see if there was any irregularities.

I ran the 741 cam with stainless marine wet bravo tails, and had no reversion

You sure its not something silly like an intake leak???

Also,,,, what do you idle at in gear just out of curiosity

I am leaning towards the intake not being sealed properly. I will make sure that the intake is on perfectly. I was not happy about how tight the bolts where for the intake. Is there a specific lbs that should be put on those bolts. It runs about 650rpm at idle but I always make sure I bump up the throttles to keep rpm's up. I don't think it's cracked but Is there a way to pressure check the intake? I think I can rule out reversion now.

Stainless marines are a great set up and I use them all the time on 525's instead of tubular headers however you need to put high heat permatex on both sides of the gasket that sits between the manifold and the riser because if it isnt,100 percent sealed it will cause water to enter into the engine..Jerry from stainless will be the first one to tell you this..

Yes jerry did mention that to me. But if it was reversion then all of the cylinders on that side of the engine would have had the carbon cleaned off of them not just one right?

Good point.

Jersey also you mentioned torque on intake bolts and yes they are typically torqued to 25-30 and needs to be done in sequence and increments. Unfortunately if your bolts did loosen enough as you mentioned it's doubtful tightening and and torquing to specs would solve your problem. I thought I read that you mentioned you discovered water On top of 7 piston which I can't help but think that this problem has something to do with your exhaust. Did you pressure ck that exh manifold? If you do pull intake just follow proper procedure reinstalling. Everyone has their own technique etc which is fine as it's not rocket science however just a little tip you can follow or not. Up to you but I use a little high tac on the head surface to hold in place along with a little bead of permatex around the water passage as well on front and rear of block in place of the two gaskets supplied in some kits.

I really doubt this is your current issue though. Even with your intake bolts not being very tight after hours of use your intake has a tendency to take a set so to speak creating a vacuum like seal.

Re: I went back to your original post and did see you pressure checked exhaust. I didn't mean to question that again. Just really trying to help get your problem solved. What gen engines you have? Also you have twins correct? Your problem is just on the one engine that you had ground and replace the cam in?

do you have the cam card yet from the engine builder?

Getrdunn thank your advice. Yes the builder said that he checked the manifolds when the issues arose. Yes the intake are off both engines are on engine stands. The problem is with both engines And Both cams where replaced. Engines are 1998 gen 6. I have he cam card for the cams that are in the engines now which I posted. I forgot to get the old cam card today. But it was taken off of the 741 platform 114lsa. Ground at predator cams. But like people have said that cam which is in there now should not cause reversion with the set up I have. Thanks again guys. Chris