Merc 470 oil in sump

[clydey]

Hello eveyone, Joined today after reading posts on this site and believe there is a good crowd here to answer ?
I hate to beat a dead horse but just purchased a boat with a 1984 merc 470 and understand some of the problems with this engine,but here's a stumper for me. The engine runs smooth when looked at before the purchase.Got it home and put the muff to it and started to warm up to change the oil.When I pulled the dipstick I had the dreaded milky oil.Sucked it all out,pulled the filter and did a compression test....."1 cyl.120..."2-125...3-125...4-135.Installed new plugs,oil,zinc and filter ran for 5 mins and milk is back. Now let me add when I removed the first oil that was bad I got way to much ..like 2 gals. Antifreeze looks fine and none lost.So here's the real ?. Is it possible that not starting the engine first and running water with the muff that it got in through the exhaust?

 

[stonyloam]

Re: Merc 470 oil in sump

Is it possible that not starting the engine first and running water with the muff that it got in through the exhaust?

Not likely. Was it water or antifreeze in the oil? Is the weep hole on the lower starboard side of the engine waterpump clear?

 

[clydey]

Re: Merc 470 oil in sump

Had to be water from the muff.Anti freeze tank is full.Can't seem to locate the weep hole you mention..Sorry my first inboard

 

[stonyloam]

Re: Merc 470 oil in sump

It is very hard for water to get in that way. The water exits in the downhill side of the elbow, so would have to fill the exhaust, then back up into the exhaust manifold, leak in past the valves, and then past the rings into the crankcase. So getting past the rings in any appreciable amount would be very difficult. You would probably have a cylinder full of water and hydrolock if that were the case. That engine has a lot of oil in it any, about 6 quarts, and a little water will cause milky oil. You will want to do a cooling system pressure test (borrow tools from Autozone). In the meantime locate that weep hole and make sure it is clear.

 

[clydey]

Re: Merc 470 oil in sump

OK found the weep hole.Because of the alt it's not easy to see. It is clear of obstruction.Any other ideas???Does that pump on the engine pump coolant or fresh water on the 470?

 

[Eric 3.7LX Alpha 1]

Re: Merc 470 oil in sump

The engine pump circulates coolant. The drive impeller circulates seawater.


Pic of the weep hole:


Flow diagram for our engine:
http://i777.photobucket.com/albums/yy59/solar7647_album/coolantflow.png

 

[Bamaman1]

Re: Merc 470 oil in sump

The 470 is a very simple engine, however they're a slightly different animal. The good news is that your compression is stable. They're like an automobile engine with the closed cooling system--but with the heat exchanger.

You'll probably have to pull the top end off the engine, find the problem and fix it. The engine is also famous famous for having a seal problem on the front of the engine. Some Mercruisers eventually have cast iron rusting problems with their intake and exhaust manifolds. Any good auto engine mechanic could probably diagnose and fix your problem.

If you need a head, I've got a fresh one with zero hrs. since a quality rebuild. I also have a full unused gasket kit.

Good luck!

 

[stonyloam]

Re: Merc 470 oil in sump

If there was a seal problem there would be antifreeze leaking from the weep hole, that is what is there for, to allow leaking antifreeze to drain out rather than go into the crankcase.

 

[Rake722]

Re: Merc 470 oil in sump

It sounds like what I found when I first got mine.

As Terry said, weep hole would weeping if it were the cam seal and there would be loss of coolant.

My bet is on the riser. This would leak water into pot 4 if it were the case. I ended up fitting a new Ex Mani and Riser to cure the problem.

It sounds like the exact same symptoms I had on mine. Compression good, no loss of coolant, water in the oil but not coolant.

 

[clydey]

Re: Merc 470 oil in sump

Thanks everyone...Rake722 how did you determine that is was the ex manifold and riser????Is there a way to test ??

 

[clydey]

Re: Merc 470 oil in sump

After doing some research on what the risere does that could be it.What other parts are needed to do that job?

 

[Rake722]

Re: Merc 470 oil in sump

Thanks everyone...Rake722 how did you determine that is was the ex manifold and riser????Is there a way to test ??

Well it was a case of it being the only place where ingress of raw water could account for the symptoms.
As mentioned above if there is no coolant loss or coolant in the oil it rules out the cam seal, head gasket where there would almost certainly be coolant loss.

The only place that remains is the riser. When the passages between exhaust gasses and cooling seawater collapse - thats when water has access to Cyl. 4 in particular. I used a process of deduction rather than a test.

The other small bit of advice is if you have the cast iron manifold, if you try to separate the riser from the log, I have been told that there is then little chance of being able to put them back together as the mating surfaces will be shot due to rust.

One thing you may be able to do is pull the spark plugs and see if the one from pot 4 looks washed out.

 

[clydey]

Re: Merc 470 oil in sump

Well that is not the best news. I have not tried to separate them as of yet. I found a riser for $200 but that mani looks to be a grand. Not what I want to spend on this thing as the whole boat was only 2,000.Anybody know where you get these cheaper???I also hate to not repair because I like the boat.Maybe after a couple homebrews I can talk myself into it.lol...Also I will need all the gaskets for this job to,Iboats must have them I hope.We need a 470 grave yard for these parts to get at a resonable cost...Thanks for the help rake722

 

[clydey]

Re: Merc 470 oil in sump

Well that is not the best news. I have not tried to separate them as of yet. I found a riser for $200 but that mani looks to be a grand. Not what I want to spend on this thing as the whole boat was only 2,000.Anybody know where you get these cheaper???I also hate to not repair because I like the boat.Maybe after a couple homebrews I can talk myself into it.lol...Also I will need all the gaskets for this job to,Iboats must have them I hope.We need a 470 grave yard for these parts to get at a resonable cost...Thanks for the help rake722
One more thing and this may sound to easy but is it possible that the gasket between the manifold and the riser crapped out and replacing it would solve this issue. I did check and the mani I have is cast but the mating of the 2 looks really clean

 

[Rake722]

Re: Merc 470 oil in sump

Hi clydey,

When I took mine off I removed the manifold and riser together.
I spent 2 hours with a hammer and screwdriver separating the riser from the manifold and the engineer who told me I'd have a hard time putting them back together was 100% correct.

Not a snowballs chance in hell of those to ever being successfully mated again.

It cost me ?920 UK to get the replacement manifold and riser kit from Mercruiser. They do a kit to replace the whole kaboodle.

Beleive me I know how you feel. My boat cost 3500 uk and I have spent what seems like a further 3 K making her right again and it does not stop. I thought I was finally there only to discover that my MR lower unit has been filled with filler and will cost a further grand to replace.

I am now considering whether to cut my losses and sell but am heart broken after the intimacy I have built working on this boat over the past year or 2.

If no one else chimes in to confirm what I have told you then it maight be worth a trip to the breezeworks to get confirmation, but I think the writing is on the wall.

Dont just change the riser, you should get the mani too if you intend to keep the boat as these parts will soon be NLA.

 

[clydey]

Re: Merc 470 oil in sump

Thanks for your input.....I will try and separate first and if that is not possible will decide then what to do.Happy sailing.