newbie to o/bs, have a 120hp force with water in block

[IMPATIENT 1]

hi everyone, my name is tom. been a gm master tech for 14yrs, married 13, have 3kiddos, and i'm a gearhead been runnin jet boats for the past decade and with the economy crashing, it was time to put the 1000+hp boats behind me for a yr or so.

here's my issue, maybe someone has been up against it before:

i have a 1998 maxum with a 98 force 120hp on it. i bought it right before thanxgiving, drove 150 miles to check it out , did the basic check over, compression test etc.. everything looooooked fine, boat is supppper clean and well taken care of, services well logged. i get home , wk later i take the boat out and discover what feels like a ignition misfire. just like you'd feel if a plug wire was breaking down or burnt/loose. well i found the coil wire on #1 was corroded at the coil, along with the coil lug screw good and rusty. i ordered a fresh coil and wire, bolt em on, muff up, and still have a misfire on #1 i check the plug and its alil wet with milky stuff, runny peanut butter contaminated oil i guess. i figured headgasket was blown, i yank the head off, nope headgasket looks fine(compression on all for at 130psi, tested before head pulled). i check the head for warped, can't get a feeler under my carbon straight edge, so i put a new gasket on and muff up once again. still gettin #1 plug wet.
somehow water is getting into the block, then the scavenging port on the top 1/2 of the crankcase sends that milky crap up the #1 and injects it, kills the plug. i ran the motor with the scavengin hose off the top port and the milky stuff just steady gets shot out under pressure. it made about 2 cups of it within 3minutes of run time, so its not just left over condensation in the block, this thing is injesting water somewhere i pulled the exhaust chest down and can't find anything wrong there, plate is perfect, both gaskets unharmed, no visible cracking on the cooling ports/jacket. i've never overheated this thing, but who knows what happened before me. i've bought boats that i knew the owner was filling my full of chit, but this guy was not that kind, he was very straight forward and just not the type. he took great care of the boat and would have definately fixed this if he'd noticed.

tonite when i get home i'm pulling the top intake and see if i can spot a crack anywhere in the block. anything else i should look for? i have no clue where this water is coming from i've checked the basics. appreciate any help, me and my 9yr old twin boys are ready to fish, no boat to fish outta of

i guess i did't pay enuff attention to the plate lol

 

[IMPATIENT 1]

Re: newbie to o/bs, have a 120hp force with water in block

forgot to add that when i 1st got the boat i put in a new water pump kit, complete kit not just the impellor. the old impellor wasn't damaged of anything but had been in a couple yrs., i wanted to know for sure, so i changed it the head water passages are corrosion free, very clean internally and had never been opened up prior to me removing the head and chest covers, the paint on all the bolts were never broke lose.

 

[roscoe]

Re: newbie to o/bs, have a 120hp force with water in block

Betting on the exhaust plate gaskets on the side of the block.

http://www.mercruiserparts.com/images/FORCE/855376.R2/11.png

 

[IMPATIENT 1]

Re: newbie to o/bs, have a 120hp force with water in block

Betting on the exhaust plate gaskets on the side of the block.

http://www.mercruiserparts.com/images/FORCE/855376.R2/11.png

close! it was the plate itself, woohoo. i was up till 3am last nite wondering what my wife was gonna do to me when she found out i was ordering a new powerhead did a lil more research on the site and just made myself a list of the failures and repairs here that had fixed internal leak issues, this place is a great source!
i'll take a pic tonite and post it tommorrow. about 1/2 way up the plate, there's a 2inch crack. i guess it was sucking in the water from the exhaust chest. i wanna go ahead and replace the reeds since i already ordered a master gasket set for it. want it runnin flawlessly , may as well do everything on it that may fail i read the reeds fail on them often and i highly doubt this 1 has ever had any.

any idea who has the best online prices for the plate and a set of reed valves?