Hydrolock Prevention

[Arc]

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.

 

[Cartouche]

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

 

[Ken Ongemach]

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

 

[Martin J]

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.