Another water in oil thread... Just can't get this one sorted.

Had a perfectly operating engine pulled for a peace of mind rebuild. 750 hours or so, compression had fallen low in a couple cylinders, but otherwise good operating 502 Mag MPI in a 1999 Baja 232.

Upon getting the boat back (a year later, but that's a story for another day) found water in the oil after a couple hours running it.

After tearing down again, I get a "report" that the manifolds have a crack that only shows up when hot. Ok fine, they are a couple years old, but never leaved when the boat was brought in. So new manifolds go on, and after an hour of running, water in the oil.
Other things I've been "told":
Oil cooler pressure tested
Heads checked
Intake manifold checked..
Risers replaced with tested used ones as mine were "questionable"

Mechanic is working with me.. but we're no further ahead after 1.5 years of this..(again another story of excuses and delays).

Where do I start looking for this water intrusion?

1.5 years of this I would not believe one word the "mechanic" said

Probably would not even believe the motor was rebuilt, but also don't know that much so far as what has been said

Yep..there is that too. Decent sized shop, been in business for decades..I have to believe that they are somewhat capable.. Its no performance shop, but they appear capable

That engine is one of the most basic marine engines to work on, I dont see where they are capable. what does this mean ? Heads checked..Intake manifold checked..

I agree, the heads need to be pressure checked. Some things can’t be seen without this process. BTDT.

It could be something as simple as them using the wrong gaskets, not thread sealing through drilled bolts holes, who knows

I just read an article about something similar about someone getting water in the oil.....my first thought was thread sealant on cyl head bolts......but the 502's that i have seen so far have all had blind holes so that wouldn't apply. But what did catch my eye in this article is the use of lube under the head bolt washer...here's a copy/paste from it:"You didn’t mention this, but it’s also entirely possible that if the engine assembler did not put sealant on the threads then he probably also did not place lube under the bottom of the head bolt. This is important because roughly 50 percent of the torque required for a bolt of this type is used up in overcoming the friction between the back side of the head bolt and the head. If the head bolt is dry, this radically increases the friction in this area.

This may not sound all that important, but an increase in friction here along with dry threads increases the friction in both areas. When torqued to the specification—let’s say 65 ft.-lbs., this means that far less tension is applied to the bolt to create the proper clamp load on the gasket. It’s difficult to offer a number but the clamp load on the gasket could be reduced by 20 to 30 percent because of this oversight."


The other thing they talk about is torque wrenches...

"Another real possibility is that the head gasket allowed coolant or water to leak into the engine. It’s possible that the head bolts were improperly torqued or that the bolts were under-torqued. This happens because the torque wrench has not been calibrated in a long time (if ever). A non-calibrated wrench could easily report torque far below the 70 ft.-lbs. required. All the above steps will help.

Another indication of a weak clicker torque wrench is if the user leaves the torque setting applied and does not return the adjustment back to its lowest setting. We performed a test where we left the torque setting at 65 ft.-lbs. for 60 days and the wrench lost almost five percent accuracy. What this does is weaken the adjustment spring that triggers the audible click. Leave it at the high setting for a year and the wrench could lose 10 percent of its rated setting. A loss of 10 percent at 70 ft.-lbs. drops the torque to 63 ft.-lbs."



Just some food for thought

And that's why I have a digital setup that I use to make sure my torque wrenches are good to go. And they're always stored with all tension removed.

Sounds like head gaskets are leaking to me - mismatched gaskets will also do it (intake especially).

or possibly around the valve guides? what was done to the heads?