Water entering via exhaust?

Mar 11, 2015
2
Catalina 30 Tall Rig Vancouver
I've got a Catalina 30 Tall rig with Yanmar 22hp engine. At revs over about 2800 rpm, the stern is pulled down enough that that exhaust is pretty well under water. Then, there seems to be seepage of salt water into the hold.
So, two questions - is it normal for the stern of a Cat 30 tall rig to sit down that far under higher revs? Second, does anyone have any experience of water coming in through the exhaust system.
FWIW: the stuffing box is tight, with no leakage, and a new rebreather was installed last fall and is in excellent shape.
 
Nov 8, 2007
1,523
Hunter 27_75-84 Sandusky Harbor Marina, Ohio
Hull waves...

If you watch a boat slowly accelerating in calm water, you will see that the hull generates waves along its side you may see 3 to 5 at slow speed. As the boat goes faster, the waves lengthen, and there are fewer of them. Finally, there is just one wave with one crest at the bow, and one at the stern. This is why you see higher water at the stern as you get to 2800 rpm. On our boat, this hull wave actually backs up a little water into the cockpit through the cockpit drains.

When the hull waves reach this point, the boat is really sitting down in the wave, and which makes it hard for the boat to go any faster. This is the cause of the “hull speed” phenomenon. The boat can move out onto the wave at its bow (this is called “planing”) but it takes a lot of power to overcome the hull wave.

I would check the sealing of your exhaust to the stern, and the integrity of the exhaust hose itself. Water was coming into our boat through a crack in the cockpit drain hose. A mysterious leak that only occurred when we were sailing at or near hull speed.
 
Mar 11, 2015
2
Catalina 30 Tall Rig Vancouver
Thx to David & Greg. Will check the embedding.... Also good to hear that sinking into the wave is normal...
 

HMT2

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Mar 20, 2014
899
Hunter 31 828 Shoreacres, TX
May want to examine your mixing elbow as well, they can develop pin holes that will grow.