milky oil from port engine

i have 2 4.3 mercs, the port engine appeared to be running at a high temp ( guage was reading around 190 ) but assumed the gauges were broken) during my survey the tech measured them and temps were normal, opened the engine hatch and noticed a puddle of milky oil from under the port engine, as well as milky oil from the dip stick. i know this is a huge issue, having my mechanic come out this week to give it a look. any idea what the issue may be ? and also worst case scenerio, any where to start looking for a new engine ? thanks for the help

Hmmm, sounds like a blown head gasket to me. Are they fresh water cooled? I know in the Chevy Blazer's they had a lot of trouble with the 4.3s and the cooling system.

Leaky oil cooler? Did they run normal except for the temps?

Way too little info. Is this a saltwater boat? Hours? Maintenance? Flushed every time?
Yes, engines can be saved with the right actions preformed immediately. You need to drain the oil, pull the plugs, fill the crankcase with marvel mystery oil and squirt in the plug holes. Motor the engine over and drain to flush it out. Repeat until the oil is clean.

You have a good chance the heads will need to be replaced if it is a saltwater engine not flushed good and RWC. I have had this happen to me even though i flushed it well(around 950hrs) and helped a friend change the heads on both of his engines for the same thing(around 500hrs).

You may want to get a complete drop in ready to run engine with warranty. It can be changed in about 12 hours if you know what your doing. Good luck let us know how you do.

Thanks guys, had a mechanic out today, checked the oil from the dipstick, still milky, he wanted me to see if the engine would start, it did. He noticed that there was water leaking from the oil cooler, he had me run the engine up to around 1500 rpm while not in gear, engine sounded fine, no vibration or sputtering. Shut the engine down. He is calling mercury tomorrow, and a mechanic who is very very skilled with the 4.3 mercs. But he believes it is the oil cooler, said that its possible that would allow water into the oil. The engine is pretty up there in hours ( 750 ) and raw water cooled in the ocean. and yes engines did seem to run normal except for temps, but mechanic thinks the guages are bad.

We didnt do a compression test yet, he seemed to think that we didnt need to but is clarifying with mercury. previous owner had boat always winterized and all maintainence done as needed, with new risers / manifolds put in last year. i am hoping the mechanic is right, being the oil cooler, fingers crossed, thanks again for the help.

I had an oil cooler go. When you shut the engine off my failed oil cooler sucked salt water into the engine. Close the sea valve and remove the cooler ASAP to stop any more salt water from getting into the engine. I changed the oil 4 times in 8 hours after I replaced the cooler and the oil was still milky. A 6 hour run cleared the oil and I changed it again. All is fine 1000 hour later.