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Old 07-03-2020, 04:05   #1
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Engine and sea water

Need some thoughts here. My boat's engine has less than 200 hours but has had raw water enter the engine from a failed pump seal over an extended period of time (but less than 20 engine hours) which has caused some internal corrosion. I'm currently staring down the barrel of replacing the whole show with a new engine and gearbox - something I'd really prefer to avoid if at all possible. Here's a picture of the camshaft gear that drives the PTO gear used by water pump">raw water pump and represents the worst of the corrosion.

I was going to go with a new Yanmar (the old engine is a Misubishi based unit), but it's a lot of coin and it's nagging at me that the current engine might be economically salvageable.

Am I with this motor or is it at least worth a partial tear down and inspection prior to biting the bullet and ponying up for a new Yanmar?
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Old 07-03-2020, 05:02   #2
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Re: Engine and sea water

My two cents...

Assuming the engine had plenty of life in it before the water pump seal failure, I would be trying to repair whatever damage has been caused in the last 20 hours of sea water ingression.

(EDIT - re-read that the engine only has 200 hrs, so yes, it should have plenty of life in it).

The very least I would do is to pull it apart and have decent look inside.

I suspect the damage will only be superficial and not seriously affect the reliability of the engine.



Start with a compression check then pull and inspect the head and assuming there are no show stoppers at this point, pull the pistons and oil pump.

If you have the space and time to do the work yourself, it will most likely be a whole lot cheaper than re-powering.

What model engine is the Mitsubishi?
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Old 07-03-2020, 10:49   #3
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Re: Engine and sea water

Change the oil a couple times and you should be fine. Cruise somewhere so the engine reaches full operating temperature before the oil change.
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Old 07-03-2020, 16:39   #4
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Re: Engine and sea water

I agree with Wotname and lepke about giving it a chance to live. And they both are more knowledgeable than I, as well.

Once you get it torn down, you'll be able to see what needs to be done. Rings may be shot, may need to re-bore cylinders, valve seats will need attention, and exhaust valves, may be lappable, may need replacing. Nothing too major, really, but you have to see it to tell for sure what needs doing.

It is the sort of thing that with a shop manual and parts diagrams, someone can work out.

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Old 07-03-2020, 18:17   #5
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Re: Engine and sea water

Thanks guys, that kind of mirrors my thoughts. The engine is an S3L2 (a ~30Hp motor) which is nine years old now but only was in any form of sea service for about two years due to a series of unfortunate events, including being sat in slightly brackish bilge water to the top of the sump for a while when brand new , so it certainly has done some hard time.



One more thing. AliExpress has no shortage of vendors selling rebuild kits of various components to suit these engines. Anyone had experience using similarly sourced parts?
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Old 07-03-2020, 18:25   #6
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Re: Engine and sea water

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Originally Posted by Reefmagnet View Post
.....

One more thing. AliExpress has no shortage of vendors selling rebuild kits of various components to suit these engines. Anyone had experience using similarly sourced parts?
Not directly but a mate reported he was currently having trouble getting some stuff out of AliExpress due to it being mainly in Wuhan and the Covid-19 lock down.

Dunno how widespread it is.
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Old 07-03-2020, 18:43   #7
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Re: Engine and sea water

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Originally Posted by Wotname View Post
Not directly but a mate reported he was currently having trouble getting some stuff out of AliExpress due to it being mainly in Wuhan and the Covid-19 lock down.

Dunno how widespread it is.

It's a problem, but I think that they have started removing the quarantine conditions from regions outside of Wuhan. I just received order of LFP batteries from Shenzhen this week from an order placed on the manufacturer in early January. The seller was very upfront about the problems they were having and advised that they were given permission to return to work in late Feb. I also have another small AliExpress order that is now on it's way that was ordered later, but held up also. So I'm reasonably confident that I can get delivery in a month at this time.


Not that I'm adverse to sourcing parts locally. The S3L2 isn't the most popular mainstream industrial engine around in Oz so local supply is a little limited.
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Old 07-03-2020, 18:49   #8
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Re: Engine and sea water

ReefM, FWIW the following maybe helpful.

I am currently doing a really slow rebuild of a 2QM20 that had suffered a serious raw water pump seal failure allowing large quantities of salt water into the engine.

I don't know the full history except to say it had clearly been turning oil into milk for quite some time (months or years). I do know that it could turn fresh oil into milk after a couple of hours of running. Apparently it had been running with the emulsified oil for quite awhile.

It then sat under a house for a couple of years before I got it. It was starting and running when it was removed from the boat.

By the time I got it, it had no compression.

So far I have only pulled the head. The valves are badly pitted although I think the valve seats will be OK. The guides are fine. There was a heap of rust on the rocker assembly but it has cleaned up OK.

I drained the oil and oil filter and filled the crankcase with diesel and spun the engine over (without the head on) to circulate the diesel. Did this a couple of times and then flushed with new oil a couple of times (and fitted new oil filter).

One cylinder has a rust patch and the other looks OK. I haven't measured anything yet but at the worst case, I might need a new liner.

One cylinder / piston was holding diesel and the other wasn't. After letting diesel sit in each cylinder both for some weeks, both sets of rings seem to have freed up. I will know more whenever I remove the pistons. Quite possible they will be OK and only need new rings.

I did remove the sump plate after flushing the crankcase and everything inside the crankcase looked surprising clean. The sump plate itself was still covered with a heavy milky sludge which suggested to me the engine had been running on the milk for some time.

Anyhow, the purpose of this post is to say your engine is fairly likely to be in a way better condition and once you pull the head, you should know whether to proceed or not.
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Old 07-03-2020, 19:34   #9
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Re: Engine and sea water

Quote:
Originally Posted by Wotname View Post
ReefM, FWIW the following maybe helpful.

I am currently doing a really slow rebuild of a 2QM20 that had suffered a serious raw water pump seal failure allowing large quantities of salt water into the engine.

I don't know the full history except to say it had clearly been turning oil into milk for quite some time (months or years). I do know that it could turn fresh oil into milk after a couple of hours of running. Apparently it had been running with the emulsified oil for quite awhile.

It then sat under a house for a couple of years before I got it. It was starting and running when it was removed from the boat.

By the time I got it, it had no compression.

So far I have only pulled the head. The valves are badly pitted although I think the valve seats will be OK. The guides are fine. There was a heap of rust on the rocker assembly but it has cleaned up OK.

I drained the oil and oil filter and filled the crankcase with diesel and spun the engine over (without the head on) to circulate the diesel. Did this a couple of times and then flushed with new oil a couple of times (and fitted new oil filter).

One cylinder has a rust patch and the other looks OK. I haven't measured anything yet but at the worst case, I might need a new liner.

One cylinder / piston was holding diesel and the other wasn't. After letting diesel sit in each cylinder both for some weeks, both sets of rings seem to have freed up. I will know more whenever I remove the pistons. Quite possible they will be OK and only need new rings.

I did remove the sump plate after flushing the crankcase and everything inside the crankcase looked surprising clean. The sump plate itself was still covered with a heavy milky sludge which suggested to me the engine had been running on the milk for some time.

Anyhow, the purpose of this post is to say your engine is fairly likely to be in a way better condition and once you pull the head, you should know whether to proceed or not.

Thanks Wottie, that is very helpful! I think water has been getting into this engine in very small amounts since prior to the layup 5 years ago. I have (another) gut feeling that the oil does protect surfaces to some degree from corrosion even when it has salt water mixed in with it. Of particular note, the cast aluminium rockers and covers, even in the worst exposed location, appear unaffected. Best I can tell from Internet research is that the water is detrimental when running, but it's hard to find cases where the water has sat for a while in an unused motor. For reference, this is what engine parts look like when oil can't get to them (courtesy of an emulsion "seal" forming in the bearing), but salt water can.
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Old 07-03-2020, 20:10   #10
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Re: Engine and sea water

Quote:
Originally Posted by Reefmagnet View Post
..... I think water has been getting into this engine in very small amounts since prior to the layup 5 years ago. I have (another) gut feeling that the oil does protect surfaces to some degree from corrosion even when it has salt water mixed in with it. Of particular note, the cast aluminium rockers and covers, even in the worst exposed location, appear unaffected. .......
Was the water and oil emulsifying i.e. making the oil milky?

If not, I guess the water sat on the on the bottom until the heat of running help dry it off leaving the salt behind. I have no idea if salt and oil mix but I reckon some reader will!!!
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Old 07-03-2020, 20:11   #11
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Re: Engine and sea water

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Originally Posted by Reefmagnet View Post
...... For reference, this is what engine parts look like when oil can't get to them (courtesy of an emulsion "seal" forming in the bearing), but salt water can.
That's ugly!!!!!

I will be interested to know what the final results will be.
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Old 07-03-2020, 21:13   #12
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Re: Engine and sea water

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That's ugly!!!!!

I will be interested to know what the final results will be.

I haven't got a photo of that gear cleaned up, but just wiping it over with a rag cleaned it up on removal. It needed new bearings, although the rear one was still "serviceable" if there had been no other option. After a proper wire brush and clean and new bearings installed, the gear was fine with only some minor pitting on the face of the shaft seen in the previous post's picture. I'm guess that most of that gunk came from the remains of the water pump which no amount of cleaning was going to de-uglify!
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Old 08-03-2020, 08:42   #13
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Re: Engine and sea water

It actually looks far better than what I expected from the description
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Old 08-03-2020, 09:14   #14
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Re: Engine and sea water

Question: is there a scenario where you can flush the crankcase a few times with diesel fuel (filling, cold-crank, drain, repeat) without tear down? If where water intrusion is caught soon enough and/or relatively small amount?

Aerated/hydrated oil is deadly on lower end bearings. But simple moisture over time is tough on pistons/cylinders/valves. How much of each condition do you think a diesel can sustain with just mild wear?
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Old 08-03-2020, 09:36   #15
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Re: Engine and sea water

I think it's worth a shot to save it. My main concern would be cleaning it out and the crankshaft bearing surfaces. Abrasive rust particles in the oil on those surfaces could definitely make for short engine life. Rust throughout the system will keep breaking loose. Not a fun deal to do this, but vs thousands of dollars for an engine..... I dont know of anything that will lubricate but also remove rust at the same time...? The best situation would be to remove the engine and clean everything, but most especially those crankshaft journals and bearings.

Short of that, I would open as much as possible with the engine in place and remove all the rust you can, run the engine with lightweight oil at minimal load and rpm, change oil, repeat if you see any coloration in the oil. This could be all overkill, but from the pictures there's a lot of rust going on in there.
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