Vent holes on transom leak in a following sea when under full power

[Chuck.Philips]

We have an '05 Mk II 34 with two small vents on the swim step that "appear to leak" water under the aft cabin bed. It only seems to happen when we are under full power and in a following sea. Then I can actually see water sloshing over the swim step toward the wheel.  I'm contemplating trying to seal the 2 vent holes from the inside to stop this leaking.  I have not noticed any water even in the bilge when we are just under sail or not under full power.  The transom area is always dry under sail.  Has anyone else experienced this situation and if so, what did you do to rectify it? 

I'm not sure what purpose the two vent holes serve and don't want to cap them if they really serve a purpose.  Anyone know this?

Thanks

Chuck Philips
#1725--Forever Young

[Jon W]

I have a MK1 so can't help with what they're for, but if you choose to rebed/seal them do it from the outside not the inside. Sealing from the inside risks damage by trapping the water.

[ewengstrom]

Any above water plastic/marlon thru hull is subject to UV damage. Our anchor locker thru hull fitting was cracked when we bought the boat but the crack was undetected unless the boat was cutting a bow wave thereby covering the thru hull, then it leaked and filled the area forward of the V-berth with probably 20 gallons of water before we noticed it. When I went to loosen the nut holding the thru hull in place the entire thing just broke off in my hand.
Inspect all thru plastic/marlon thru hull fittings very, very carefully.....it might prove interesting.

[Jim Hardesty]

I'm not sure what purpose the two vent holes serve and don't want to cap them if they really serve a purpose.  Anyone know this?

Not sure what you are calling vent holes.  Shamrock has 2 vent fittings, metal, one vent for aft water tank, one for fuel tank.  Also has 1 or 2 small plastic  thru-hull fittings closer to the water line, they are cockpit drains.  Takes a bit of crawling into the aft lockers to check all the hoses are connected and in good shape.  This discussion may help.

https://c34.org/bbs/index.php/topic,10656.msg82841.html#msg82841
Jim

[Robert Mann]

Chuck, I believe Jim is correct.  Our boat is 2002, number 1622 and I have the same two vents. One for the fuel tank vent line and the other the aft water tank overflow.  You shouldn't get water into the aft cabin from those unless the fittings are really deteriorated.  I also find water under the aft cabin, plywood center section floor.  This also happens when we wash the boat.  I'm thinking our swim ladder needs to be resealed to the platform.  Trouble is I don't fit very well into the aft compartment to catch hold of the nuts. 

[Ron Hill]

Chuck : You have us all trying to guess about these 2 vent holes that you mention??  Take a picture so we can see what you are talking about. 
Then maybe we can help you out with a solution. Just can't figure out what you are talking about that is down the height of the "swim-step"??? 

A thought   

[Chuck.Philips]

I took everything out of the two stern compartments yesterday and tracked down the vents and hoses attached to them--they were attached to the drains on either side of the cockpit.  Both sides were a little loose, the one on the starboard side was really loose.  I tightened both hose clamps up and will check to see if we get any more leaks on a sail next week to Dana Point. 

Thanks to all who gave me ideas as to where to look.  I really appreciate this organization.

Chuck