Mercruiser 470 raw water in oil

[Max-Falcon]

Hi,
My dad got a 1987 Searay with Mercruiser 470 (165hp closed cooling - Serial# B624565) that been sitting for a few years. Couple of weeks a go we decided to run it.

We put fresh gas and it started right up! after burning all the fogging crap (lots of white smoke) engine was running very smooth actually! Then I noticed there is no water coming out of transom exhausts holes, just dry exhaust like a car exhaust was coming out! after 10 min or so idling engine overheated and I shut it down quickly.

I replaced the Thermostat and then rebuilt the water pump in the outdrive and changed gear lube. Upon water pump rebuilt I found the impeller had no fins ( just the core left!) and water guide tube that is on the water pump housing was melted! Everything in the upper unit seemed intact including the water pocket cover and the guide tube. After these 2 fixes the engine never overheated again on muffs. Now a good stream of water gushes out of transom exhaust hole but only from the starboard side. From the exhaust on the port side I still get only exhaust gases with a very minimal spray of water! So question #1 is this normal or same amount of water is supposed to come out of the exhaust hole on the port side?

With overheating issue resolved I then changed the engine oil and filter and took the boat to the lake! at the lake engine worked very well, good torque and speed. But after 10 to15 minute of cruising at various RPMs even near WOT I checked the engine and noticed splash of milky oil on the rocker cover. I Checked the dipstick and that confirmed I got water in the oil. I shut the engine off and used the little kicker to go back to the dock.

After further inspection it looks like I got raw water in the system. I say this because of 2 reasons; 1- I pressure tested the closed cooling system and found no leak (pumped 15 psi, dropped to 14psi in 10 min or so and stayed there for almost an hour) and reason 2 is that I could not feel any AF scent in the milky oil. Also I don't see any leakage from the weep hole and the hole is open.

Question #2 is in what ways raw water could get into Merc 470 engine and to fix it which part should I replace first?

Sorry for the long story and thank you

 

[matt167]

Once you cook a 3.7/ 470 you'll be replacing stuff. I don't see how raw water can get into the oil on one, but coolant finds it's way very easily through the head gasket

 

[nola mike]

The relief holes in the transom are connected, so angle of the boat can affect the discharge. However running it dry for that long you probably cooked your exhaust boot and flappers. Possible that you have a burnt rubber bit clogging something. With the overheat you likely blew your head gasket.

 

[Scott Danforth]

raw water in the oil is a bad exhaust manifold to elbow joint

agreed, running without water for more than a few seconds will burn up the exhaust hoses, flapper and any other rubber bit that has a maximum temperature of 250. (exhaust and water is about 210 degrees - pure engine exhaust is well over 1100 degrees)

the over-heat will have taken out your head gasket.

 

[Max-Falcon]

raw water in the oil is a bad exhaust manifold to elbow joint

agreed, running without water for more than a few seconds will burn up the exhaust hoses, flapper and any other rubber bit that has a maximum temperature of 250. (exhaust and water is about 210 degrees - pure engine exhaust is well over 1100 degrees)

the over-heat will have taken out your head gasket.

That's where I started actually! sort of...
After rad pressure test passed I changed the oil and filter and started the engine on muffs. It started right up and worked fine. After a few minutes I checked the oil dipstick and oil looked clean. But I could see water accumulating gradually around the rockers in the valve cover.
Then I started disassembly. First disassembled the riser which is a combo unit with reservoir in my boat. 3 of 4 bolts came out easy but 4th one fought until I snapped it! ( just a quick advice, if these bolts don't come out with reasonable amount of force then force is not the answer. More importantly if you snap a bolt just call it a day and take it to a machine shop! don't get creative!)
The riser had a hole in the water jacket! What is in the water jacket of the riser/res combo? is it coolant or raw water?
Then I took out the manifold (one bolt on the same corner acted up but this time I applied heat, industrial grade penetrating lube and 45 minutes patience and got it out in one piece!) The manifold looked very good mainly because it is the aluminum type. only the 4th cylinder port is corroded/chipped. Machine shop said I need to get it to a welder to build up that port with filler. If anyone has experience with welding aluminum manifold plz share!
I got out the upper exhaust elbow which looked fine, again probably because it is aluminum. The rubber exhaust bellows, specially the large one that connects riser to upper elbow, is pretty cooked inside! I haven't gotten to the lower elbow where the shutters are to inspect them but something tells me I won't find them there anymore!
with the a few variables out of the equation I am planning to do another coolant pressure test and leave it over night. If this pressure test is ok then would it confirm the the head gasket is fine?

 

[nola mike]

If this pressure test is ok then would it confirm the the head gasket is fine?

No, you can have a hg failure that doesn't affect the coolant jacket, or the failure won't show up at 15 psi.

 

[Max-Falcon]

Just an update... I drained the oil that I said was clean at the dipstick tip and it was badly milky!! My plan was to drain the oil and get the oil drain plug out and pressurize the cooling system and leave it over night to see if water/coolant will drain our of oil pan! Since the manifold is out I plugged two 2" hoses that connect to the manifold from the front and the back and stuck a tire valve stem in a piece of hose and clamped it to the i think 1/2" hose that was unattached from the reservoir (Red arrow in the photo). Then pumped 15 psi air in the system. I checked multiple times with soupy water to make sure the plugged hoses don't leak. But now unlike a couple of days ago when I did a rad pressure test the cooling system won't hold the pressure. It leaks all the air in like 30 sec! Are there more hoses that I need to plug or leak is internal?

 

[Max-Falcon]

raw water in the oil is a bad exhaust manifold to elbow joint

Just to make sure my riser doesn't have internal leak... when i pour water through the seawater intake of the riser (the short tube on the side) water flows to the exhaust chamber of the riser. I am guessing when the part is installed that's how the seawater exits the system. This is how riser should work right?