MD7A Water in oil

[Compass790]

Great you dodged a bullet! Sorry if I'm asking the obvious but does it have a sump plug?
Or any oil lines/fittings that go to sump bottom that you can remove?
Is it a raw water cooled engine? If so they dont run very hot so would take a fair while I'd guess to evaporate the water. Our raw water cooled engines oil temp after 2 hrs running fully loaded is only 59C
Maybe try flushing with WD40 or CRC 5-56 & turning over decompressed as Wotname suggests if you don't want to pull the sump cover off. Just a thought, can't say I've tried it but I would in yr case.

[hpeer]

So a few years ago I started a trip with my MD7A after it sitting for a prolonged time. The first 3 legs were like 60mi, 100 miles, and 60 miles. All motor sailing or straight motoring. At the end of leg 1 I noticed some milky oil. I suspect simple condensation as the motor had been sitting under a tarp outside for a winter. Ditto at the end of leg 2, still milky. But with no repair facility handy I carried on into leg 3 which would bring me to someplace where I could do something or get help. By the time I reached the end of leg 3 the oil was clear of all milkiness (sp?).

The engine has run perfectly since that time 4 years ago. No repeat.

These engines run cool, any little water in the oil will take a looong time to evaporate out. But evaporate out it will, eventually.

I don’t know the risks of letting that strategy, if there are any.

[Compass790]

Had another idea for you to try,
If you can find a fresh water cooled thermostat to fit use one of those. I'd modify one to fit if necessary if you use your boat in fresh water exclusively & leave it in there. The reason for this is it will run hotter & evaporate any water much faster. It's generally accepted fresh water cooled engines last longer & run better anyway at their higher operating temperature. Quite a few people convert their raw -water cooled to fresh water cooled.
I would certainly do what i suggest with our raw water cooled engine if it was a fresh water boat

[Shawn67]

Think this is the thermostat you would want for fresh water cooled.

https://www.ebay.com/itm/Volvo-82981...EAAOSwlV9WR5Ve

The tricky part is I've seen that part number used for the typical 60 degree raw water thermostat as well as for the 75 degree thermostat. The temp will be stamped on the thermostat itself.

Another possibility https://www.ebay.com/itm/Thermostat-...UAAOSwpcxbQwlE

If you are just trying to get the engine hotter to boil out the water just pull the thermostat out all together. On the MD7 that will actually tend to make the block run hotter as it lets all the water just flow through the exhaust manifold and out the water injection port. The thermostat really acts as a sort of flow balancer between the water through the manifold and through the block. I wouldn't leave it this way but if you were just trying to get it hotter for a bit this would help. Don't do this with a raw water engine used in salt water though. Watch block temperature with an IR thermometer. Your built in temp gauge would probably read cooler as it is measuring water temp in the exhaust manifold.

Shawn

[Pavel24]

We are going for 3 days sail this week end and i will watch motor closely , the next weekend is also 3 days sail , after that i plan to change oil and filter again hopefully it improves. Should give the motor at least 10h to run .

I know you can flush engine with diesel , kerosene and i guess there other stuffs but from what i have read it depends on the engine, if it was never done before it can do more harm then good . Also i think you need good place to drain it all properly so i should find out if there is drain plug under the motor and if i can access it.

PS the motor is raw water cooled ( so fresh water atm because of the lake)

[Pavel24]

i will verify for thermostat this weekend in shops near by

[Compass790]

Originally Posted by Pavel24

We are going for 3 days sail this week end and i will watch motor closely , the next weekend is also 3 days sail , after that i plan to change oil and filter again hopefully it improves. Should give the motor at least 10h to run .

I know you can flush engine with diesel , kerosene and i guess there other stuffs but from what i have read it depends on the engine, if it was never done before it can do more harm then good . Also i think you need good place to drain it all properly so i should find out if there is drain plug under the motor and if i can access it.

PS the motor is raw water cooled ( so fresh water atm because of the lake)

It will be fine to flush engine if you just spin it over on the starter motor decompressed & dont actually start it. But I'd go with the fresh water thermostat & the long run if you are worried about flushing. Agree with Shawn, you can only use the fresh water thermostat whilst boat is in fresh water tho but as I said it's better for the motor anyway.

[Bill Seal]

On a volvo MD11 (and probably a MD7) you have to remove the bottom half of the dipstick tube to get out all the oil. You can get an adjustable pin spanner cheap from Harbor Freight, or go Volvo expensive.

[Shawn67]

Originally Posted by Pavel24

i will verify for thermostat this weekend in shops near by

Consider bringing your existing thermostat. When I was searching for one it is easy to find a thermostat with the proper diameter but the height of the smaller size varies greatly. Anything taller than the stock thermostat won't fit the housing properly.

Shawn

[roverhi]

Sounds like you still have water getting into the oil. When my MD2 filled up with water, two oil changes were enough to get the oil back to its normal black color. Might try another oil change and see if the milk goes away. Problem with water in the system is the pump will be picking up water when first turned over because the water will separate out quickly and settle to the bottom where the oil pump pick up is. Close the water inlet seacock and turn the engine over with the compression releases up till you're sure the water has been pumped through and you have oil in the lubrication passages.

In any case, do not try and start the engine if you suspect oil in the cylinder(s). Water does not compress. Got my Volvo started raising the compression releases to get it to spin and then closed them. All the water hadn't been evacuated from the rear cylinder and ended up with a shortened rod. Fortunately it was just a matter of replacing the rod, piston and getting rid of the anti-syphon valve and all was good.

[Pavel24]

After this week end the oil is back to looking like oil at the deep stick level and oil filter and the engine runs smoothly . But now i have more white acumulation on top of the engine , i quess it is because of the evoporation.

Running motor in neutral at low rpm for few hours with out the oil cap ? Maybe it can help water vapor to escape ?

maybe stupid idea

[Compass790]

Did you get a fresh water cooled thermostat for it? Running in neutral at low revs will hardly make it warm. Much better to run it at cruising revs under load.
Yea the white crap will be from water evaporation
Not sure about oil cap off. Couldn't do it on our Yanmar, too much oil spray.
Good news motor sounds ok, would hate to be rebuilding a volvo from the parts prices point of view

[Pavel24]

No , i didnt find the right thermostat near me . For now i am not sure i still need it .