milky oil in merc 3.0 - what to do now?

I don't know how much of this is coincidence or helpful info, but this is my day in full.......

So I changed the oil about 1 month ago, the old oil that came out was old but not abnormal looking and I replaced it with a standard 10w40 (thats all I could find) boats was running great for a few weeks, then the other day I went out and about 5 minutes under way there was what sounded like a really loud backfire..... I throttled back and headed for calmer waters to investigate, gave it a bit more throttle and another really loud backfire and a hesitant feeling about 2k rpm, I pulled the plugs and no.4 cylinder was wet and I couldn't confirm a spark from that plug, swapped it out for a spare I kept on the boat, fired right up and hesitant feeling now gone... Except now engine was overheating at high rpm, ok now im thinking the impeller has gone too, it's about a year since I changed it so it's probably due for replacement (i run in salt water) limped home and pulled the boat to change the impeller + plugs + clean HT leads cap etc......

So now i'm thinking I can drop in back in and check if all is ok, but 1st check the oil... Horror, it's a pale brown milky colour, not at all gloopy and the viscosity looks right, just the wrong colour.... This is the 1st time i've encounter this problem and i'm not sure where to turn next.... Any help greatly appreciate.. Engine details are in my Signature.. It's about 6 yrs old I think

Thanks

Chris

Re: milky oil in merc 3.0 - what to do now?

Was the oil level higher up on the dipstick than you recall it being after your oil change? This would be a sure sign of water intrusion VS a little condensation.
I would start off by doing a full compression check on all cylinders, paying close attention to the figures from cylinder 4.

Re: milky oil in merc 3.0 - what to do now?

Six years in salt water... I would suggest pulling the riser and see what you find there. Salt water is hard on the exhaust manifold and riser.

Re: milky oil in merc 3.0 - what to do now?

Sorry, it's only been in salt water for about 1 year of the 6, but will start with a compression test and post the results, cheers

Re: milky oil in merc 3.0 - what to do now?

Walker600 said:

Sorry, it's only been in salt water for about 1 year of the 6, but will start with a compression test and post the results, cheers

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Ayuh,... So what is the oil Level,..??

Is it rising,..??

Re: milky oil in merc 3.0 - what to do now?

Bond-o said:

Ayuh,... So what is the oil Level,..??

Is it rising,..??

Click to expand...

It seemed slightly higher than maximum, and I filled it to about maximum, but the boats not level atm so I want to level it off and check again...Will check again later today and let you know...

Re: milky oil in merc 3.0 - what to do now?

So, i've not been able to find a compression tester, gonna go hunting over the weekend, but checked the oil again today and it was up by maybe half an inch, I noticed some rust around the exhaust manifold/riser gasket, so pulled the riser and it looks as tho the gasket is most likely the issue. I need to have a good scrub to confirm, there were defiantly signs of water intrusion on the exhaust side altho the metal is still lovely and thick and looks fairly healthy,,,(will clean and confirm) it was the spark plus in the piston closest to the riser that was looking a bit poor when I pulled it, could this be water draining from the riser elbow into the last cylinder when the engine wasn't running!?

Also pulled the connector piece off down to the lower exhaust pipe and found a metal bar across the pipe with nothing on it.... Is this the exhaust shutter? Is it important and what does it do? Finally if the shutter isn't attached to the support bar could it have fallen off? the outdrive is off at the moment and I didn't see anything from the engine bay or behind the stern.... I didn't try fishing around in there tho.....

Thanks again and will post results of compression test when I find/make a compression tester!

Re: milky oil in merc 3.0 - what to do now?

Stop taking things apart until you check the compression. from your symptoms,overheating and missing water shutters it sounds like you blew a head gasket.

Re: milky oil in merc 3.0 - what to do now?

if ya got water in the oil. ya need to read this.
especially item #1. save the engine.

there's also a sticky thread on water in the engine. which also refers to the above link.

Re: milky oil in merc 3.0 - what to do now?

Walker600 said:

could this be water draining from the riser elbow into the last cylinder when the engine wasn't running!?

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Sure - very possible. When you clean the mainifold and riser you will want to see at least a quarter of an inch of clean shiny metal - not black carbon / rust.

Walker600 said:

Also pulled the connector piece off down to the lower exhaust pipe and found a metal bar across the pipe with nothing on it.... Is this the exhaust shutter? Is it important and what does it do? Finally if the shutter isn't attached to the support bar could it have fallen off? the outdrive is off at the moment and I didn't see anything from the engine bay or behind the stern.... I didn't try fishing around in there tho.....

Click to expand...

Yes - that's the remains of your shutter. I would definitely go "fishing around" to see if any remains are still there. As to the importance... well, a lot of guys take them out and never have any problems. BUT they are there to keep the water from backing up into the exhaust - like for a sudden deceleration, etc. Cheap and easy to replace.

Re: milky oil in merc 3.0 - what to do now?

possibly the seal has gone and waters is getting in im not 100 percent but ring a marine mechanic and they should be able to tell you over the phone what the problem is
i had a similar issue with mine but no backfire

Re: milky oil in merc 3.0 - what to do now?

Hey guys, the exhaust gasket arrived today so i'm going to head in the city tomorrow and pick it up, hopefully while im there i'll also find a compression tester or the necessary materials to make one, will post the results asap!

Re: milky oil in merc 3.0 - what to do now?

hey, so two pieces of information today..... I bought some bits and pieces to make a compression tester today, not really what I wanted to buy but it was all i could find, the check valve was desgined for water not air and i was suffering a bit of leakage, but the results were as follows - 90-90-80-75, they're consistant but those numbers strike me as low, before I had a problem the engine was running sweet so I can't imagine the engine is worn out.. any thoughts?

Also, regarding the joint between the exhaust manifold and riser. Having split the two the exhust manifold has 4 slots for the water jacket, but the riser only has 3 inlets.... going through google i have found pictures of both, both claming to be direct manufacturers replacement's for merc 3.0, to add the the issue the gasket that arrived today only has 3 water holes in it, and altho the rear water hole is sealed from the exhaust outlet, it doesn't cover the rear water outlet on the exhaust manifold to prevent water from being pumped into the bigle...... what the hell is going on here!?

cheers
chris

Re: milky oil in merc 3.0 - what to do now?

Update, after being concerned with my last compression test results and the engine seeming to run (idle and high rpm) ok, I did some looking around and it would appear that I didn't perform the compression test properly, 1st I hadn't warmed up the engine, and second I didnt have the throttle open, so I retested today following the correct procedure and my results were - 115, 120, 120, 130 - Thats looking alot better. So I guess now its a case of waiting for the bellows service kit to turn up, refit the outdrive and head out for a sea trial......