Adjust the rockers again, something is wrong. You didn't modify the cooling system that much, so reinstall the t stat to make it function like before the change in rockers and exhaust. Save your sanity, keep it simple and adjust the rockers again.

Compression test will be done tomorrow.
Did not rejet carb yet. I'll check the plugs while doing the compression test
Is the 140 thermostat the correct one for my application? (with the bypass of course)
Yes I'm in Fresh water.
Boat weighs 4100 lbs dry.

Thanks for all the good info, I appreciate it!

Are you sure they are 1.7 rockers.Did you grind the corner rockers because they won't fit under stock valve covers.I put pro magnums in mine and I had to shorten the nuts and remove the drippers.Are you sure somthing didn't hapen over the winter that posibly damaged the motor such as rust from water ingestion.Maybe do a compression/leakdown test.The reason I ask is I built a zz 502 last winter and did a few mods to resist reversion.That cam is set at 104 atdc intake lobe center line.I had my intake lobe retarded 4 degrees and modified the sprocket to set it at 110 atdc.This widened my lsa to 112 .You cant play with these cams much as far as grinding or the lifters will fall out of the retainers due to lack of base circle diameter.I also modified my stainless marine exhaust to be dry to the tips(3" straight pipe welded to the inner exhaust tube and slip pipe clamped for the outer water passage).Of course this ment ditching the silent choice.Even with these mods to the motor that should help eliminate reversion it still reverts like crazy at idle.If I let her idle at 700 for a minute and pull a riser there is water pooling in the manifold.I control it by using an idle selenoid when the boat is running in nuetral and avoiding low rpm situations.I only idle down for shifting.As long as the idle is 900 or better it wont revert.I always rev her up in neutral before shut down at the end of day.You want good exhaust valves to take the abuse.I got suspicious when I was getting steam at idle but not at high speed idle.I know the older HP 500 motors with gills had this ploblem and Merc just recomended the rev up thing at shut down.I don't know if you decked your block but if you went for minumal deck height this motor is in the 10:1 range and you want to be careful of too much timming.If you didn't the excesive quench could be even worse.Its really hard to here the detonation,usualy you feel the loss of speed.If you got headers I would put piros in.Another issue I had was the high oil temp.I would see 270 at the filter mount in about 5 minutes of full throttle but the water temps were always stable at 140.I used an edie 3" x 18" cooler.It takes forever to warm the oil and if you don't run it hard enough (like on a rough day with wife and kids) it wont reach the212 point.Bagging on it I hit 240.I havn't had enough time to realy fine tune mine but I'm spinning a 23 mirage plus to 5350 in a 5000# 24 degree performance boat.The best speed is 69 mph on gps.I have a holly 800 cfm double pumper with 96/86 jets and the timing is set at 32 total.I think I could tweek her some more but it seems to run pretty good now and I prefer to tune on the safe side.I don't want to here that ugly ratling noise and find piston chunks comming out the carb again.Your motor should be making more power with the cam set in the stock manner but your splitting hares with compresion and valve timing for a reliable heavy use motor.I boat on big water and will cruise at 4500 for an hour straight at times.I had other issues with this motor out of the crate such as faulty block and poor head machine work but overall its a good pile of parts to start with.Hope you get her dialed in.

I should also say be carful of over proping.I tuliped a set of valves once by using too large of prop and too low of octane fuel.The boat came up to speed then started slowing down.I melted all the plug ground straps.I had the motor apart for other reasons that year and the intakes were all tuliping wich is a good indicator of detonation.I would use good fuel and not prop for less than 5000.I would also check your tach.Mine was out at higher rpm.My boat is almost 26' and the slipage numbers are down at 12%.I would think yours should be better but your at 18%.Is the hull OK?

HMIRAGE mentions the oil temp. Very important! I'm running a 454 mag cooler now and like HARRISON I can get oil temps to 270* in very little time. Hence the new/bigger cooler {Hardin Marine 3 x 22 incl. power steering}. When I see oil temp at 250 or so, I back off the throttle. If you don't have an oil temp gauge it might be a good idea to install one.

I added spacers under the valve covers to clear the gold rockers.
Having the marina check compression and re-adjust the valves today. Also double checking the carb numbers to see if I have what I think I have.

Thanks again!

Update: Guess you really have to worry about people they let work on boats. Went to do the compression check and found 3 of the plugs the marina had just put in were loose and number 8 the porcelain was broken in half. On top of that the #8 was one of my original plugs. Did do a compression check and had 200# in every cylinder.
Also found the large exhaust house at the back of the boat was leaking so I have an exhaust leak on top of a bad plug and 3 loose ones. I'm thinking the combination should be all or most of my problem.

Figured out that the carb was a 850 double pumper and not a 750, which the marina had also told me wrong. How on earth can you not tell the difference in a vacuum secondary and a mechanical?

Good for you Formula242, Those are easy fixes. The most important fix is not to go back there.. 200psi comp test is real good. she should scream now. Have fun...

Yes easy fixes are good. nothing major!
I'll let ya know tomorrow how she runs

Thanks everyone for all you help

Was the guy that did the plug work the same one that installed the roller rockers??