Multiple bilge pump holes on one side - proximity

[keith]

I have a '72 23' SF and I installed 2 2000gph rule pumps. One pumped to port and one to starboard. I would like to leave the existing 450gph that is wedged in at the stern under the oil pan to remove excess water out of the bilge after wash down. My question is about drilling another hole in the side of the boat that will have to be within 4-5" of the existing hole. Is this ok? How close is too close?
The existing hole is for 1 1/8 id hose and I think it is 1 3/8 hole and the other pump would be a 1" I think.

Thanks for the advice.

[CHANCE1234]

i believe plenty of guys have multiple overboard discharges on the same side within inches of each other. I don't see a big deal with it. You should be just fine. Happy drilling...

[thehermit]

Here is what I did. No issues after 6-7 yrs. One is a 500 auto pump and one is 2000 switch (float and dash). Both wired direct to separate batts.

[Islandtrader]

I had all my bilge pump holes on the same side...but I put them on the side starboard side so when driving I could look over the gunnel and see if any thing was being pumped out.

[keith]

Thanks everyone. Someone told me not to drill a hole within 9" of another hole for structural purposes. They must have been referencing a lesser quality boat!
I was going to try to offset the holes to get more distance but I like the looks of Hermits stacked setup better.

[bigeasy1]

I did the same as hermit.A 2000 and a 1500 gph pumps with outlets on one side, zero problems.I took an additional small 500 gph pump and mounted it on a stip of aluminum flat, and slid it all the way back against the transom face and under the engines oil pan (I/O) so that I can get all the water out of the bilge
I cant see how two outlets would make any significant weak spots in the hull, especially way up high where your outlets are.I wouldnt lose any sleep over it.

[htillman]

I put the outlet for the pump that is on constant auto on one side so if I see that is comes on there is a problem that needs immediate attention. This pump was also mounted a little further forward than the other pumps.

[Bushwacker]

Originally Posted by keith

. . . My question is about drilling another hole in the side of the boat that will have to be within 4-5" of the existing hole. Is this ok? How close is too close? . . .

Depending on the stress field, a couple of smaller holes (known as shielding holes) adjacent to a larger hole can actually reduce the concentrated stress around the large hole! It's common practice to install such holes between bolt holes in the flanges of compressor and turbine disks on gas turbine engines! The extra holes cause the loads and stresses to redistribute so there are more gradual changes between holes such that the maximum concentrated stresses at the edges of the big holes are significantly reduced. You can find some guidelines for stress concentration factors vs. hole size and spacing in a Machine Design textbook or a Mechanical Engineering Handbook.

[Rufneck]

I recently placed both bilge pump discharge ports side by side on the port aft corner of the boat. Mine is a Sceptre (starboard helm) so I figured it would be easier to see the discharge on the port than on the starboard.