Mercruiser 5.7 EFI Water in Oil

[sarnone]

Hello and thank you to whoever reads this post.
My starboard engine is a 1998 5.7EFI 260hp with a Bravo III sterndrive. I winterize every year according to the mercruiser manual and add anti-freeze to the cooling system. I do this in my backyard on my hoist, where is stays fully covered for winter. This year, after only using the boat three times and only the last time on plane, I winterized to find milky oil but no noticeable change in level. I also got some small rust chunks out while draining the cooling from the 6 plugs. I changed the oil and ran it for 15 minutes. Checked the oil and it wasn't totally milky again, but was probably any remaining oil before the change.
I probably only put 10 hours a year on the boat over the last couple of years. I drive it like a grandma and idle it a lot. I have had it for maybe 8 years. Yes, it could probably use new risers, manifolds. It always runs trouble free and doesn't overheat. It does however look like it has had the risers or exhaust worked on, or work in general, before me because the riser bolts are painted, just a guess. Both engines are close in serial number and made in 97 I think and have 1000 hrs.
I think I have to:
1. pressure test cooling - how do i do this?
2. check oil cooler - how do I do this?
3. check risers?
4. check exhaust?
5. check intake?

I am hoping to get some confirmation on next steps.

Thanks
Steve
"whosoever calls upon the name of the Lord shall saved"
Romans 10:13

 

[alldodge]

Have a motor serial number?

Are you in fresh or salt water?

 

[Bt Doctur]

Exactly how was it winterized? If you sucked it in thru the muffs and did not drain the syatem first, you probably cracked something

 

[Scott Danforth]

Being on the hoist, I suspect salt water

If your risers and manifolds are older than 5 years, check there first

Agree with above. If you are draining everything first, you are ok. If you rely on a single point or 3-point drain, most likely the lower drain hoses are plugged. Inspect everything

If you used a block-buster suck up AF kit..... You need to inspect everything

Start with a cooling water jacket pressure test

 

[sarnone]

Have a motor serial number?

Are you in fresh or salt water?

I apologize for not responding. My account was locked and I could not reply. Engine Serial Nol.: 0L067794
Freshwater

Thanks!

 

[sarnone]

Exactly how was it winterized? If you sucked it in thru the muffs and did not drain the syatem first, you probably cracked something

Sorry for the late reply, my account was locked.
I raise the boat above the water, pull the raw water hoses and lay them down, crank it over for a split second to get an remaining water in the pump, remove the 6 cooling drain plugs, then fill the engine with coolant from the large hose at the thermostat housing. I do not use an suction kits or muffs.
Thanks in advance.

 

[sarnone]

Being on the hoist, I suspect salt water

If your risers and manifolds are older than 5 years, check there first

Agree with above. If you are draining everything first, you are ok. If you rely on a single point or 3-point drain, most likely the lower drain hoses are plugged. Inspect everything

If you used a block-buster suck up AF kit..... You need to inspect everything

Start with a cooling water jacket pressure test

Sorry for the delay. The boat is in freshwater and has always been before I owned it. The risers and manifolds are definitely older than 5 years. I do not use a kit to take up antifreeze. The engines have a 6 point drain system and I pull the hoses to the raw water pump as well.
Since my post, inspection of the gasket joint between the elbow and manifolds shows signs of rust, scale and mineral deposits. I think I might just take those off and inspect.
Thank you for help.

 

[alldodge]

Thanks for the SN
Being in fresh water the exhaust should last longer then the boat.

The easiest thing is do a compression test, might be a head gasket

Cooling system test
Disconnect hoses from exhaust manifolds and one from thermostat housing coming from the raw water pump. Plug 2 of the 3 connections and connect air compressor with regulator to the 3rd. Pressurize to 15 psi

You don't have a oil cooler but do have a power steering cooler. In any case that's not the issue

To test exhaust pull elbows off mans and see if gasket looks ok.
If gaskets are ok, plug water hose fitting on bottom of man and fill with acetone, see if there is a leak. If no leak remove plug and drain acetone into container

 

[sarnone]

Thanks for the SN
Being in fresh water the exhaust should last longer then the boat.

The easiest thing is do a compression test, might be a head gasket

Cooling system test
Disconnect hoses from exhaust manifolds and one from thermostat housing coming from the raw water pump. Plug 2 of the 3 connections and connect air compressor with regulator to the 3rd. Pressurize to 15 psi

You don't have a oil cooler but do have a power steering cooler. In any case that's not the issue

To test exhaust pull elbows off mans and see if gasket looks ok.
If gaskets are ok, plug water hose fitting on bottom of man and fill with acetone, see if there is a leak. If no leak remove plug and drain acetone into container

Alldodge, for the compression test I need to be back in the water to protect my impeller, correct? And what do I disconnect so it doesn't fire when cranking?
Also, for the on engine manifold test, where am I looking for leaks? Inside the exhaust manifold through the elbow connection?
Thank you very much.

 

[alldodge]

Alldodge, for the compression test I need to be back in the water to protect my impeller, correct? And what do I disconnect so it doesn't fire when cranking?
Also, for the on engine manifold test, where am I looking for leaks? Inside the exhaust manifold through the elbow connection?
Thank you very much.

Don't know which drive but can put some muffs on the drive or put it back in the water.

You should have a kill switch, pull it and motor won't start, even better remove connectors going to the coil

When manifold is filled with acetone it should stay full. If it leaks out then it has a crack somewhere. Acetone is thinner then water and it will leak out where water will not with a cold manifold

 

[sarnone]

Don't know which drive but can put some muffs on the drive or put it back in the water.

You should have a kill switch, pull it and motor won't start, even better remove connectors going to the coil

When manifold is filled with acetone it should stay full. If it leaks out then it has a crack somewhere. Acetone is thinner then water and it will leak out where water will not with a cold manifold

Alldodge, would you happen to know the compression range for this engine? 120?
Thanks
sarnone

 

[Scott06]

Alldodge, would you happen to know the compression range for this engine? 120?
Thanks
sarnone

New compression with an accurate gauge is 150 psi. When its starts getting below 115 give or take, or you have a big difference between cylinders you have issues.

If low a leak down test can be used to pinpoint where you are loosing it. Can also put compressed air in the cylinder and see if you get air pressure coming out through the cooling system, intake/exhaust valves, or into crank case (rings).

You need to have engine up to temp, all the spark plus out, and throttle wide open.

In fresh water unless you missed draining a manifold normally the exhaust will last the boat lifetime. Did the boat ever overheat? Can also rot out under the thermostat as well.

Does the boat get up to operating temp. If thermostat doesnt work and the engine runs cool and you rarely use it you can get condensation build up in the oil.

 

[Lou C]

To check the manifolds with acetone you have to remove them from the engine & remove the elbows. Be careful because acetone is very flammable. You can clean up the mating surfaces with a mill bastard file & then check them for flatness with a straightedge & feeler gauges. Should be less that .003” variation. Being that you have a 1998 you still have wet joint exhaust so it is possible to get water leaks in that joint which will run down the center exhaust passage into the cyls via an open exhaust valve.

 

[sarnone]

New compression with an accurate gauge is 150 psi. When its starts getting below 115 give or take, or you have a big difference between cylinders you have issues.

If low a leak down test can be used to pinpoint where you are loosing it. Can also put compressed air in the cylinder and see if you get air pressure coming out through the cooling system, intake/exhaust valves, or into crank case (rings).

You need to have engine up to temp, all the spark plus out, and throttle wide open.

In fresh water unless you missed draining a manifold normally the exhaust will last the boat lifetime. Did the boat ever overheat? Can also rot out under the thermostat as well.

Does the boat get up to operating temp. If thermostat doesnt work and the engine runs cool and you rarely use it you can get condensation build up in the oil.

Scott06, this engine gets up to operating temp more slowly than my other engine, the difference is several minutes. It has never overheated since I owned for the 7-8 years. Both engines are capable of the exact same rpms at wot. The rpms are at spec for both engines, i don't remember that rpm value. Everything else aside they always run great and I am hypercritical of any odd sounds coming from them. The last couple years I kept the engines below planing speeds. The last trip from the gas station this year I ran them at about 4000 rpms. I warmed up the oil to remove it, attained operating temp, and then noticed the milky oil.

Is the leak down test you are referring to adding the compressed air to the cylinders?

thank you

 

[sarnone]

To check the manifolds with acetone you have to remove them from the engine & remove the elbows. Be careful because acetone is very flammable. You can clean up the mating surfaces with a mill bastard file & then check them for flatness with a straightedge & feeler gauges. Should be less that .003” variation. Being that you have a 1998 you still have wet joint exhaust so it is possible to get water leaks in that joint which will run down the center exhaust passage into the cyls via an open exhaust valve.

Lou C, thank you. I am trying to understand the path if it leaks at the exhaust manifold. So I assume when this happens when the engine is off and water leaks into the cylinder and down past the rings, right?

thanks

 

[Scott Danforth]

compression test wont impact your impeller. it wont be spinning fast enough to damage the impeller.. however if you want to run some water down the line feel free.

 

[Scott06]

Scott06, this engine gets up to operating temp more slowly than my other engine, the difference is several minutes. It has never overheated since I owned for the 7-8 years. Both engines are capable of the exact same rpms at wot. The rpms are at spec for both engines, i don't remember that rpm value. Everything else aside they always run great and I am hypercritical of any odd sounds coming from them. The last couple years I kept the engines below planing speeds. The last trip from the gas station this year I ran them at about 4000 rpms. I warmed up the oil to remove it, attained operating temp, and then noticed the milky oil.

Is the leak down test you are referring to adding the compressed air to the cylinders?

thank you

this is a leakdown tester. It outs a known pressure of compressed air into a cylinder and measures the residual pressure the cylinder holds. Leakdown is measured as a % leakdown . <5% is great, start getting over 10% you have an issue.

What I was mentioning is just putting compressed air in the cylinder , a poor mans leakdown essentially so you can see where it comes out.

 

[Lou C]

Lou C, thank you. I am trying to understand the path if it leaks at the exhaust manifold. So I assume when this happens when the engine is off and water leaks into the cylinder and down past the rings, right?

thanks

yes it will usually partially fill a cylinder

 

[sarnone]

yes it will usually partially fill a cylinder

Lou C, understood. But being thicker than gasoline or combustion gases, how does it get pass the rings into the case? What are your thoughts on that?

Thank you for your feedback
Steve

 

[Lou C]

The sealing of the rings is not 100%. I had a similar problem with a different (likely) cause. I my case it was leaky head gaskets that allowed water to seep into 2 cyls after the engine was shut down & cooled off. That put a fair amount of water into the oil over about a week. When I took it apart to replace the gaskets I had the cyl heads inspected and as it turns out the heads had small cracks from a previous overheat which also damaged the head gaskets as well. However the boat ran fine with no apparent water in the oil for 2.5 years after that overheat. Reman heads new gaskets & cyl head bolts got it back up & running and no water in the oil for the last 6 seasons since the repair.