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That also keeps the ballast tank from escaping thru the locker drain when the boat heels...


Eerrrrrr....how much are you heeling ALX?..

Gentlemen - thank you for taking my excessively long-winded explanation in good spirits...I was concerned that it might come across offensive in some way or another. I love getting into these technical discussions and sometimes...well...just get carried away.

So back to one of my earlier questions...has anyone done this on an S or D model boat where the vent is in the back under the stairs?

vizwhiz wrote:Gentlemen - thank you for taking my excessively long-winded explanation in good spirits...I was concerned that it might come across offensive in some way or another. I love getting into these technical discussions and sometimes...well...just get carried away.

Hey, good times! I enjoyed the respectful conversation too! I didn't mean to run on like I had a hook in my craw. The kitchen sink experiments were great! At least no one turned " ", like can happen in the Back Room.

Catigale wrote:That also keeps the ballast tank from escaping thru the locker drain when the boat heels...


Eerrrrrr....how much are you heeling ALX?..

If you look at an end-on diagram of the ballast tank's, the side tubes, and draw a line from the outermost limit of the ballast tank tube ( either side ) there to the anchor locker drain directly, that line's angle to level will represent the limit of heel before ballast begins to escape. Turn the diagram until the line is horizontal. It is a significant difference from the line between the ballast tank's side tube to the underside of the deck at the farthest point forward in front of the anchor locker.

Note that the anchor locker drain and the higher point under the deck forward of it will both be getting lower relative to the ballast tank tube as the boat heels further, so every bit of height possible is important for an open ballast vent hose.

Having started to modify my vent valving I noticed the following 1.as we don't have the horsepower ie only 15hp we can't drain on the move so all draining takes place on the ramp....we drive forward untill drainvalve at rear is out off the water and observe water coming out.I haven't timed it but as I have lengthened the vent tube the time it takes seems to have increased ???? ie are we creating a partial vacuum in our ballast tank by the small vent tube inability to allow enough air flow....my thoughts also ran to introducing air under pressure to the vent valve BUT stopped....how many square inches are there in the ballast tank and what PSI would damage things.My biggest problem is the other people at the ramp.....all in a hurry and not inclined to wait 10-15 minutes????....we can't drain on flat land as some water is always left in the ballast tank.....we also tow with a truck so we take up a large space ie 18.5-19 metres which further aggravates the situation.......talk about road rage that's nothing compared to ramprage!!!

Maybe the hose you are using is too small, or maybe it has a kink partially forming in a bend. I have noticed that even if you use a thick and fairly stiff hose, when you bend it it will appear to be forming a good radius and staying open, but after a time it begins to collapse and form a sharp kink bend, which constricts air passage, especially at the onset of warm / hot weather.

I have not noticed any change of time-to-empty when motoring after doing the vent hose mod. But I admittedly have not compared the drain-time difference on the trailer.

I agree with ALX, sounds like you may have a kink in the hose (or some other kind of blockage). A 3/4" fitting/hose is plenty large enough to let enough air in fast enough because it is so thin...