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Old 01-12-2021, 07:41 PM   #21
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Originally Posted by jbbmillar View Post
On two occasions while on a mooring the seas kicked up and were hitting on the starboard aft quarter and hydrolocked my engine. Our 350 is a 2002 model with a single Yanmar 6LYASTP.


The first time was nearly catastrophic, with sea water in the cylinders, crankcase and intake manifold. Quick action after being towed 25 miles to my slip removed the water and saved an overhaul, but I'm still seeing traces of sodium in the oil analysis.


The second time happened when I was ashore and didn't think it was that rough. I returned to the boat and caught it before more than a cylinder of two flooded. Just had to pull the injectors.


This also happened to a friend with a Ranger Tug with this engine.


I now pop a 2.5qt plastic paint bucket in the exhaust outlet when not in a totally protected area.


I'd like a more permanent solution that doesn't include require spending a couple of boat units and redesigning the exhaust to add more rise.


Am I the only Mainshpper who's had this happen?


Prevention suggestions? I've considered adding a flap, but undeway the exhaust outlet orientation might make a flap problematic.
I don't understand if on aa mooring bow to - how water could come back up the exhaust and flood the motor, I would think you would have to moored stern to?
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Old 01-12-2021, 08:05 PM   #22
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Originally Posted by Cartouche View Post
I don't understand if on aa mooring bow to - how water could come back up the exhaust and flood the motor, I would think you would have to moored stern to?

Because your almost level exhaust piping is hobbyhorsing up and down and rolls the seawater right up and over the little 7-8" hump at the turbo.
Even with a waterlift muffler, it must fill the muffler first, but the same thing happens. The gooseneck aft keeps the water out and the waterlift allows you to have a gooseneck.
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Old 01-13-2021, 12:01 PM   #23
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Because your almost level exhaust piping is hobbyhorsing up and down and rolls the seawater right up and over the little 7-8" hump at the turbo.
Even with a waterlift muffler, it must fill the muffler first, but the same thing happens. The gooseneck aft keeps the water out and the waterlift allows you to have a gooseneck.
Appreciate the explanation although I know I would not enjoy anchoring if the sea state was that violent as you can see by the attached picture on our Mainship 390 - the U in the exhaust is Higher than the engine almost level with the floor, that is a heck of a rise. Glad to know the limitations
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Old 01-13-2021, 12:22 PM   #24
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Anchoring in a seaway is not a choice usually but something that happens more or less often depending on where you are and weather conditions there.

But if you have been hydrolocked at your home mooring, you have a problem.
The deciding factor is not the relationship between your spillover point and your cabin sole rather between the spillover point and the waterline which in your case is too close.
Don't take our word for it, easy to educate yourself online.
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Old 01-13-2021, 12:53 PM   #25
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Arc's post above shows a classically bad exhaust installation from the maker and a proper solution in the lower picture. It may not fix the OP's problem but others should examine their exhaust for similar bad installations
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Old 01-13-2021, 01:11 PM   #26
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Arc's post above shows a classically bad exhaust installation from the maker and a proper solution in the lower picture. It may not fix the OP's problem but others should examine their exhaust for similar bad installations

Yes and no. Yes, the lower picture shows a riser which is not completely water jacketed so is unlikely to leak into the engine when it fails. No, without knowing spillover height above waterline, both look the same and could be as bad as jbbmillar's situation.
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Old 01-13-2021, 03:04 PM   #27
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Originally Posted by Brooksie View Post
Yes and no. Yes, the lower picture shows a riser which is not completely water jacketed so is unlikely to leak into the engine when it fails. No, without knowing spillover height above waterline, both look the same and could be as bad as jbbmillar's situation.
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Yes, the overall geometry to the waterline is important as well as the entire exhaust run layout. But Bayview's point is correct with the bottom photo in Arc's post #20 case being much superior to the upper picture. Arc seems a bright fellow and I'd wager he has the geometry properly figured out.
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Old 01-13-2021, 03:30 PM   #28
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I was referring to the prevention of hydro lock or water intrusion by internal failure of the water jacket.
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Old 01-13-2021, 07:14 PM   #29
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I was referring to the prevention of hydro lock or water intrusion by internal failure of the water jacket.

That's what I thought, failure of jacketed riser. Because the two pictures, other than the jacketing vs:lagging, show the same thing and say nothing of the waterline to spillover height relationship.


"In order to fix a problem, first you have to admit you have one."
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Old 01-13-2021, 07:59 PM   #30
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Years ago, I broke the crankshaft of a single cylinder Volvo diesel in a small sailboat(a 26ft Folkboat). It had a Vetus 'gooseneck" trap and a high hose loop, but on stbd tack, well heeled for a couple of hours, water went up the above normal waterline stbd exhaust outlet, despite the protections, all the way to the engine. A flap at the exhaust exit sounds a good idea. We replaced the engine.
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Old 01-13-2021, 08:01 PM   #31
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For reference the old Cummins factory mixer was 15” above waterline . The new one I squeezed another 2” up . It’s touching the insulation on the hatch. It was manufactured by Marine Manifold , Farmingdale , n.y.
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Old 01-14-2021, 11:04 AM   #32
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Quote:
Originally Posted by Brooksie View Post
Anchoring in a seaway is not a choice usually but something that happens more or less often depending on where you are and weather conditions there.

But if you have been hydrolocked at your home mooring, you have a problem.
The deciding factor is not the relationship between your spillover point and your cabin sole rather between the spillover point and the waterline which in your case is too close.
Don't take our word for it, easy to educate yourself online.
Yep I see that thanks for the heads up- must happen a lot to people out in open water / Ocean, being predominantly on Rivers and Canals I did not even think about the problem
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Old 01-18-2021, 02:35 PM   #33
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Yes, Unfortunately this was a problem with early 350/390's & the Factory tried to stonewall it for years. Your engine & the 3126 CATS, were the big problem. Mainship blamed CAT, CAT blamed Mainship. They were BOTH at fault


When Mainship was forced to change over from the 3116 to the 3126 CATs, for emmissions, which are a much bigger engine, CAT did not have a Exhaust Riser high enough to prevent water backing up thru the in line muffler into the engine, even when running. This led to the factory (if you knew about it) to issue Service Instruction to the Dealers , to add a Surge Tube & elbow from the area in front of the muffler, back to the area, along the stbd. side all the way to the engine. Unfortunately, it didn't work. The only fix that did work was to have someone Fab, a S.S elbow, which barely cleared the underside of the deck hatch. Cost, around 4K, which the factory was unwilling to pay. So Lawsuits, including mine ensued, which, of course, no one, except the lawyers liked. So ,most plugged toe exhaust, when docked or traveled directly downwind ,in a seaway. Fortunately, by now, most owners are aware of the problem & take measures.. The damage to my boat came to about 6K.



Had the boat been able to take a water box muffler, instead of an inline unit & the original design allowed for a larger engine, all this could have been avoided. But, corporate decisions, to save a buck, prevailed over good engineering!.... Ken, Tampa
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Old 01-18-2021, 03:10 PM   #34
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Sounds like a poor installation from day one. I agree with David you need a serious rise out of the engine with a elevated muffler and the downhill run to the stern. I have attached my exhaust. Straight up some 4ft above lwl then the injection elbow falling to the silencer (on the bench behind) some 3ft above LWL The gas / water is pumped up out of the silencer some 4ft above LWL to fall some 20ft to the stern where it exits some 4-5" above sea level.
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