finn00
New Member
I have salt water in my oil, it is fresh water cooled, the mechanic says it is coming back from the exhaust. any thoughts?
water in oil
- Thread starter finn00
- Start date
RichardS
N/A
It could be coming back from the exhaust elbow if there is a hole in the exhaust port in the cylinder head but it seems unlikely as it would only happen when the engine was not running as the exhaust gas would tend to clear away the water in the opposite direction.
I think the more likely explanations are that the head gasket has blown - a compression test may well prove this, or seawater is leaking past the water pump seals depending upon whether your seawater pump is shaft driven from the crankshaft. If you seawater pump is belt driven you can discount this.
As a first step I would remove the exhaust elbow and check it carefully and check as far as you can see'feel inside the exhaust port. An inspection camera would be helpful. If you can see nothing untoward and the seawater pump is belt driven then I think the cylinder head will have to come off.
Richard
PS I've just read it again and can now see that you are fresh water cooled. In that case forget the cylinder head gasket as that would only deposit anti-freeze laden fresh water into the oil and you would see the water level in the header tank going down. However, that opens up the possibility of a leak in the heat exchanger which I think is more likely than back-filling from the exhaust. Remove the heat exchanger to check.
I think the more likely explanations are that the head gasket has blown - a compression test may well prove this, or seawater is leaking past the water pump seals depending upon whether your seawater pump is shaft driven from the crankshaft. If you seawater pump is belt driven you can discount this.
As a first step I would remove the exhaust elbow and check it carefully and check as far as you can see'feel inside the exhaust port. An inspection camera would be helpful. If you can see nothing untoward and the seawater pump is belt driven then I think the cylinder head will have to come off.
Richard
PS I've just read it again and can now see that you are fresh water cooled. In that case forget the cylinder head gasket as that would only deposit anti-freeze laden fresh water into the oil and you would see the water level in the header tank going down. However, that opens up the possibility of a leak in the heat exchanger which I think is more likely than back-filling from the exhaust. Remove the heat exchanger to check.
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sailorman
Well-Known Member
any water via the elbow is very likely to hydraulic the engine, water cannot me compressed by the piston, the con-rod will bend first or a hole in the piston.
head as stated or the heat exchanger is the more likely the cause
head as stated or the heat exchanger is the more likely the cause
VicS
Well-Known Member
antisyphon system not operating ?
Allowing water to syphon in while engine not running until it fills the exhaust stem and floods back inot the engine via an open exhaust valve.
Short term solution ... shut inlet seacock
long term solution ......... check/clean/ overhaul syphon break valve
Other possibility, depending on engine and not related to exhaust, is seals on raw water pump if gear, not belt, driven
oldharry
Well-Known Member
Cant be the head gasket on a fresh water cooled engine, surely? Salt water shouldnt be anywhere near the gasket. Is the seawater pump driven directly by a take off from the engine or is it belt driven? If its direct drive , then the oil seal could have failed allowing seawater into the sump. Otherwise it must be coming up from the exhaust as suggested by the mechanic, and you have been lucky not to destroy the piston by hydraulic locking.
rogerthebodger
Well-Known Member
Is the level of the engine oil increasing?
Do you have an engine oil cooler that is leaking as engine oil coolers are cooled by sea water.
vyv_cox
Well-Known Member
It's unusual for a cooler leak to let seawater into the coolant as the coolant pressure is almost always considerably higher than the seawater pressure. However, in some Volvos in particular, if the exhaust manifold is caked up the seawater pressure can increase enough to breach the cooler seals. However, this would not allow water into the engine, only into the coolant, which will usually overflow into the bilge.
Seawater can get into the engine as suggested if the pump is driven by the camshaft and its seals fail. Also from the exhaust manifold into the engine via the exhaust valves but this normally happens only when the engine is stopped. Can happen if the trap is not big enough or if the engine is turned over for a long time on the starter motor.
earlybird
Well-Known Member
Are you sure that it's salt water. Approx. how much?
Heckler
Well-Known Member
"
S
never ceases to amaze me when peeps say that water comes back from the exhaust and enters sump! If it comes back up exhaaust then it gets past the ex valve and enters the cylinder. To get in to the sump it has to get past the piston rings. If it was that easy for water to go past the rings then there would be no compression. My guess, either oil inter cooler, rusted through engine parts (unlikely) or most likely if the raw water pump is integral, a worn back water seal.
S
VicS
Well-Known Member
More to this than we realise
An earlier post by the OP fell by the wayside. Even this thread was day old before it attracted any replies. ..... new user syndrome strikes again I guess ....... or Mods started there Xmas hols early perhaps??
It seems that this is a big Mercruiser power boat engine to which resonators have already been fitted to try to over come this problem.
Presumably therefore it was believed that water was entering via the exhaust while running due to "valve overlap"
An earlier post by the OP fell by the wayside. Even this thread was day old before it attracted any replies. ..... new user syndrome strikes again I guess ....... or Mods started there Xmas hols early perhaps??
It seems that this is a big Mercruiser power boat engine to which resonators have already been fitted to try to over come this problem.
Presumably therefore it was believed that water was entering via the exhaust while running due to "valve overlap"
EXHAUST RESONATOR
The exhaust resonators (provided with the engine package or available separately) aredesigned to provide increased resistance to water ingestion due to the tuning effects of the exhaust system. Quicksilver resonators are designed to break up the exhaust pulses.
CAUTION!
Avoid severe engine damage. Water ingestion by the 454 and 502 cid (7.4Land 8.2L) engines may occur in some instances without the use of speciallydesigned exhaust resonators. Install exhaust resonators in the exhaust system when specified.
IMPORTANT: Exhaust resonators must be installed on 7.4L MPI, 454 Mag MPI and 502Mag MPI Models of sterndrive engines with through the transom (or through the hull) exhaust
On 454 and 502 cid (7.4 and 8.2L) sterndrive engines using through the transom or hullexhaust systems, special care must be exercised in system design and construction toprevent an adverse tuning effect on engine exhaust output.
Exhaust system tuning can be affected by various factors that are beyond the control ofMercury MerCruiser. Following are several factors that can affect exhaust system tuning:
Type and configuration of exhaust outlet.
Length of exhaust hose.
Amount of back-pressure in exhaust system.
Exhaust Resonator Kit use on Sterndrive Models:
CAN Be Used With
1. Transom mounted muffler tips.
2. Waterlift mufflers or other mufflers that are mounted outboard of exhaust elbows.
3. Open exhaust.
CANNOT Be Used With
1. Silent Choice Exhaust System.
2. Below swim platform exhaust.
3. Mufflers that mount between exhaust elbow and exhaust tip.
The exhaust resonators (provided with the engine package or available separately) aredesigned to provide increased resistance to water ingestion due to the tuning effects of the exhaust system. Quicksilver resonators are designed to break up the exhaust pulses.
CAUTION!
Avoid severe engine damage. Water ingestion by the 454 and 502 cid (7.4Land 8.2L) engines may occur in some instances without the use of speciallydesigned exhaust resonators. Install exhaust resonators in the exhaust system when specified.
IMPORTANT: Exhaust resonators must be installed on 7.4L MPI, 454 Mag MPI and 502Mag MPI Models of sterndrive engines with through the transom (or through the hull) exhaust
On 454 and 502 cid (7.4 and 8.2L) sterndrive engines using through the transom or hullexhaust systems, special care must be exercised in system design and construction toprevent an adverse tuning effect on engine exhaust output.
Exhaust system tuning can be affected by various factors that are beyond the control ofMercury MerCruiser. Following are several factors that can affect exhaust system tuning:
Type and configuration of exhaust outlet.
Length of exhaust hose.
Amount of back-pressure in exhaust system.
Exhaust Resonator Kit use on Sterndrive Models:
CAN Be Used With
1. Transom mounted muffler tips.
2. Waterlift mufflers or other mufflers that are mounted outboard of exhaust elbows.
3. Open exhaust.
CANNOT Be Used With
1. Silent Choice Exhaust System.
2. Below swim platform exhaust.
3. Mufflers that mount between exhaust elbow and exhaust tip.
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nemodreams
Well-Known Member
It would help a bit if you said what type of engine ?
How much water ?
Is the engine below waterline - is there a water lock fitted. Do you have an anti syphon lock fitted and is it working ?
If you have no external leaks of raw water - I would check condition of wet exhaust/exhaust manifold/ port - and also try to check the fresh system/exchanger with some sort of pressure test ?
How much water ?
Is the engine below waterline - is there a water lock fitted. Do you have an anti syphon lock fitted and is it working ?
If you have no external leaks of raw water - I would check condition of wet exhaust/exhaust manifold/ port - and also try to check the fresh system/exchanger with some sort of pressure test ?
Poignard
Well-Known Member
On my engine (a BUKH) the first thing I'd suspect is failed shaft seals on the Johnson s/w pump.
rogerthebodger
Well-Known Member
I understand that but I asked if the engine has an " Engine Oil cooler" which is normally cooled by sea water and thus possible to have a leak sea water to engine oil. Unlikely but possible.
I know all to well about flesh water to sea water leak as I am currently repairing my Bowman aluminium heat exchanger due to a sea water leak past the end cap O-rings due to a broken centre bolt.
RichardS
N/A
I agreed with the OP's mechanic that water from the exhaust can get into the oil sump in post #2 ........ but not because it gets past the valve into the cylinder but because a hole has corroded in the exhaust port in the cylinder head and the water can flowstraight down the oilway. We have had several threads recently with exactly that corrosion problem although, as I said in #2, I still feel that water finding it's way back up the exhaust port is not the most likely explanation which is why I suggested several others, all of which have been repeated by other posters.
Richard
smithy
Well-Known Member
I know this can happen because I have seen it in an engine in perfect condition. Like you I thought it was impossible but I suspect it may go up the side of the ex valve guide. The engine had hydro locked but fortunately sustained no damage. After the oil had been changed several times there where no further problems.
macd
Well-Known Member
Before shooting fish in a barrel, best be sure you're aiming at the barrel with the fish.
The OP is a newby and not expressing himself as well as he might. Until he does, you'd all be well advised to read Vic's post, #10, and this thread:
http://www.ybw.com/forums/showthread.php?443875-water-in-oil&p=5501819&highlight=#post5501819
The OP is a newby and not expressing himself as well as he might. Until he does, you'd all be well advised to read Vic's post, #10, and this thread:
http://www.ybw.com/forums/showthread.php?443875-water-in-oil&p=5501819&highlight=#post5501819
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earlybird
Well-Known Member
How does valve overlap allow water from exhaust to oil??
I did wonder if the problem arose from an oil test, hence post 8.
Chloride might show in v. small amount in most marine engines IMO.
Could be nothing to worry about.
I did wonder if the problem arose from an oil test, hence post 8.
Chloride might show in v. small amount in most marine engines IMO.
Could be nothing to worry about.
VicS
Well-Known Member
Dunno... never heard of valve overlap until I read in in the OP's post. Perhaps skipper stu will explain it to us. He knows all things about all engines.
Yes the Op mentions an oil test but he does not say how much water, only that it showed up in the oil test
As You say it could be so slight as to be nothing to worry about. On the other hand it could be enough to cause concern.
The OP has been on line a couple of times this evening according to his profile and he has visited this thread. Why, one wonders, is he not offering any more information or clarifying any of the points raised.
It would have been nice to have known what engine is involved and also some indication of the level of seawater contamination.
earlybird
Well-Known Member
Valve overlap is the period of simultaneous opening of the inlet and exhaust va!ves for reasons of volumetric efficiency. Usual in most IC engines, esp. those designed for higher speeds.
Can't see any relevance at all to OP's problem.
Boat engines spend their time inducting huge volumes of salt laden air.
Can't see any relevance at all to OP's problem.
Boat engines spend their time inducting huge volumes of salt laden air.
superheat6k
Well-Known Member
I would question whether your statement here that seawater pressure is less than freshwater pressure is correct. When my heat exchanger (VP TAMD60C) developed a minute pin hole puncture the fresh water system filled from the seawater, not the other way around, manifest by coolant gathering in the bilge through the pressure cap. Even at 95oC the increased pressure in the freshwater system will be less than 1 bar, but the positive displacement seawater pump will easily achieve 2 bar.
