I have a gen 6 block, i used a gen 6 cometic head gasket, the 781 replaced my peanut ports,

I ran it today at a low idle and checked plugs i saw two dots of water but not enought to mean reversion, the plugs were mocha brown..
Maybe the cometic head gasket isnt sealing as well as a normal gasket due to the facts its all metal on metal. Bc again the boat runs like a bat out of hell from 800-5000rpm havent pushed it beyond that.

Would intake manifold gasket matter if its not a marine one?

On a boat years ago, i had a leak between riser and manifold. This leak filled my 2 back cylinders full of water and hydro locked the engine. I pulled the plugs and drained the water. If you only noticed a few drops of water in oil i doubt it could be this same problem. In doubt pull risers and inspect or change gaskets.

Intake gasket may matter if its not marine given that you operate in a salt environment (I'm not saying it does, but it might).

Also, it is somewhat important to know that he was not having this problem when he had the wrong main/rod bearings installed and his oil pressure was around 35/40psi. This problem started after he fixed his oil pressure issue.

It could be a coincidence, but it baffles me that a change in main/rod bearings and an oil pump would make it start leaking anywhere. It could be that the head/intake gasket blew or a riser gasket went, but it seems weird that it never happened before the oil pressure problem was fixed.

First- stop running that engine unless you want to rebuild it again.

Remove the exhaust system, pressure test outside of the boat. For this next part you are going to have to improvise, you need to pressurize the engine with water and hold. This will require capping the water intake tube after sea water pump, and before exhaust. A flush kit, some adapters, and a low pressure gauge....you can make a kit using autozone and home depot. Don't worry about the oil cooler at this time because they usually leak the other way.

Pressurize and turn engine over by hand and look into each cylinder. Keep an eye on the gauge, if it doesn't hold at all the leak will be obvious just keep the water on. If the leak is slow you will have to use your eyes and ears.

May sound like a lot, but the other option is removing the engine.

If you know someone with a good smoke machine this job is even easier, just get the system completely dry first and follow the smoke.

Ok today i removed the manifolds and pressure tested them, the risers which are stainless marine, and oil cooler non of them leaked, So i removed intake manifold gasket which in an automotive gasket, i ordered a marine one, regardless i used rtv sealant on all water jackets, when i saw a good bond there i took off headsk, didnt see any obvious signs of water leakage with cometiv .027 gaskets, only could be a problem in head gasket since i didnt mill the block only did heads, so ill be using a marine head gasket now.... We caulked every head bolt and valve push rod retainer bolts and caulked every intake manifold bolts, well do that again and with all the new gaskets hope the best..
4 bus once i get new head gaskets and intake manifold on ill try to pressure the system up...

I also may try to get some new head bolts bottom of mine are a little corruded but threads seam fine..

Any other idea's?? I will torque head to specs of mercruiser book unless 781's need to be tighter?

The rpm airgap intake use any special intake manifold gasket or will a marine felpro be fine?

The rpm airgap intake is different from my old edlebrok performer manifold in that its has closed center water jackets and the old one had the passage through from one side to another...

Air Gap will take a standard intake gasket. Doubt if that is your problem.

First of all, invest in a quality set of new head bolts. I just learned the hard way that this is not a good area to save money. Head bolts stretch when you torque them, and reusing them might contribute to not getting even clamping on the heads/block. What are you using for sealant on the bolt threads? Standard RTV is a no-no, especially in salt water. Did you lubricate the underside of the head bolts and washers? If not, your torque readings were probably way off. Also, make sure you are using a good torque wrench, preferably one that has been calibrated recently. The cheap Chinese made ones are not recommended for a critical torque value like head bolts. Beg or borrow one that you know is good. Once again, ask me how I found out about this! :eek:

If you were just seeing a little residual moisture in the oil, I would say this is just leftover water, but since you were moving the line on the stick, you have a leak somewhere. I think I have read that the Cometics require you to have a very straight surface with a very fine, smooth finish. Were these MLS gaskets? Since you are running in a harsh salt water environment, I would invest in a good set of MLS gaskets.

Good luck!

You said "caulked the head bolts" for this round. Was this omitted when then heads were done before? That could possibly be your problem as some of those head bolts go into water passages, others into oil passages. Failure to do this might lead to water intrusion into the oil, but I am not a rebuild expert so I would like to hear more opinions on this. And this differs between blocks- a 454 has open passages but I think 502's have blind passages.

I sent heads off for pressure testing today..
Did find a couple valve guide seals broken (they were crushed and springs popped out on exhaust cylinders..)
I ordered new head bolts... $44 Napa Yes dogturd21 we used waterprooof caulk on every head bolt and yes they do go through to water jackets... When we installed cometic gasket we didnt put bonding agent on block or heads which we should have, but we didnt seem to see a head leak, regardless im using a marine gasket next round.

did you take a close look at the heads for water spotting when you got them off? If not have the machine shop tell you when they pressure test.

Was there water on the tops of any of the pistons? My suggestion to you was the engine in the boat assembled, I did not realize you were going to take it out......but good call, its the right way.

You water leak should be easier to trace with the engine apart.