I'll soon be transitioning my above deck livewell (15 gallon) into a thru hull pickup and outflow. My model hull is manufactured with the starboard thru hull drain for the middle bow compartment (drainable ice/fish box). Well, I don't use this drainable bow compartment for ice/fish. I was thinking...instead of having to core 2 thru hull locations for the livewell, why not use this existing drainage thru hull for the outflow? I mean, why bore 2 holes into a 40 year old hull when I could only need 1??
As you can see in the 1st picture below, this thru hull drain is obviously above the water line, and it's located below the level of the deck, thus below the above deck livewell. However, because of the design of this hull ('76 170), it naturally sits ass heavy. So not only will this thru hull for the outflow be forward of the livewell (to be located under elevated leaning post), but it will also be slightly "uphill". In order to reduce as much outflow tubing resistance as possible, I'd widen the thru hull drain from its current diameter (I'm guessing 3/8" or 1/2") to 3/4".
This picture below I found online. It's a skeleton view of the same model year as my hull, '76 170. The white box indicates the position of above deck livewell. Yellow line indicates livewell outflow tube, ducking below deck via pie hole cut out. The red arrows indicate the path the outflow tubing will take, under fuel coffin and forward cross brace, then hang a right towards the thru hull drain. I have read numerous times on this forum how difficult it is to manipulate this thru hull drainage tube. Luckily for me, the bow compartments drain is hooked up. So the tubing is easily accessible. And if I do widen the diameter of the thru hull, at such time I'd have thru hull access to not only secure the tubing to the fitting, but also be able to feed through the new larger diameter tubing back to the bow compartment drain.
Does anyone foresee a drainage issue?? And if so, please explain why. Here's a couple of my concerns or things to consider:
1. The outflow system must be able to passively gravity drain as much water as is being pumped in, taking into account the distance the outflow must travel uphill to exit–uphill as in "against gravity" (minimum size pump for 15gal well is 300g/min, but I prefer 500g/min)
2. When running on plane, and as the the boat pitches bow to stern, how much effect on drainage will this have
