Thru Hull Fitting Advice

I have a few questions about buying thru hull fittings for the boat and installing them. I did take a quick look to make sure that I'm not replicating another thread but there is so much info on here that I'm sure I am.

First off is there a thread that walks you through the process of drilling into the bottom of the boat and sealing the holes with 3M glue. I would really like a picture by picture walk through because honestly I am really nervous about adding these into the bottom of a perfectly good waterproof boat. I am adding 4 Johnson reversible pumps and ripping out all the 3/4 inch line for the fill and empty but the part I'm most nervous about is the drilling through the bottom of the boat part.

1. Do you use a regular hole saw, if so what size for a 1 inch fitting.

2. Should I be buying 1 inch or 1 1/8 fittings? If 1 1/8 what size hole saw do I need?

3. I understand that you run the hole saw in reverse first but there is always a certain amount of wobble in the hole saws is that going to be an issue? Do they make a diamond type hole saw and would that be better?

4. I am planning on leaving the vents 3/4 inch, does anyone know if I need a 90 degree fitting for any of these. I also wanted to know if the smaller diameter flange fittings would work for this or if I need to get the wider flange. is this area usually scuffed up underneath the fittings.

5. Also planning on putting the check valves in there to suck the bags flat. Any reason I shouldn't do this?

6. Getting back to the bottom of the boat, How much glue do you use and do you need to buy the lock-nut with the screw in it?

7. I had this done for me on the last boat I owned and it cost me 200.00 for 1 fitting, I am not prepared to pay that again, Is there someone in the forum that lives close to me (Cumming GA) that has done this before on their boat, that would like to work for BEER?

8. Anything else that I really need to look out for when doing this? I understand that you need to smooth out the hole with a dremil tool or sand paper after the hole is drilled, but any other gotcha's would be greatly appreciated.

Check this post out.

https://forum.moomba.com/showthread....rill+hole+hull

1) Yes, standard hole saw.

2) when you say fittings, do you need the thru-hull? There really isnt a big selection of 1.125" thru-hulls and ball-valves. 1" is more then plenty to feed a couple of pumps, depending on your particular setup. There is no real measurable flow advantage using 1.125" hose over 1". Its not worth the cost difference IMO. Some fittings you will use will be a 1" barbed fitting and some will be a 1.125" like the W746 and W743 Fly High female quick-connects. I would rather heat up and stretch over 1" hose, then try to crimp down 1.125" hose on a 1" barbed fitting. My suggestion would be to purchase the thru-hulls first, then measure their OD and go with the hole saw that best fits.

3) If your hole saw wobbles, you need a new saw bit or drill. Its well worth getting a quality bit from Home Depot or a Lowes as opposed to a $5 kit from harbor freight with 20 bits and a single arbor.

4) if you are going with tall sacs, the 90* vent thru-hull turned up can help reduce passive draining through the vent line. If your hole saw is a good match to the thru-hull, then a large flange is not needed. Scuffing the area is not needed IMO, but striping it of any wax, etc, before applying the sealant is best.

5) no reason not to in most cases.

6) I uses a bead of sealant around the hole on bilge side, after cleaning first, then a bead on the flange before installing. Once you get a little sealer squeezed up into the threads of the nut as its seats, the sealant will cure and it will not come loose.

8) just dont drill blind. Know where the bits going before you cut that hole. I like to use a tiny bit for a pilot hole first. Then I can see where it came through to make sure im not going to be on a trailer bunk or something. If all looks good, then proceed with the hole saw.

Thanks guys for the info, Anyone ever tried to use one of the diamond type hole saws? Would one of those be preferred.

1) Used a regular wood hole saw myself-went thru the floor with no issues at all

2) 1" fittings

3) had no wobble myself so not sure, but dont think it should

4) vent holes are able to take 1" fittings

5) yes on the check valves, makes the bags look like a raisin

6)a nice wide beam of silicone, locking nut not used on mine or from the factory, when you tighten the nut the excess silicone comes out

7)plan to be in Georgia middle of July, will work for cold beer, always willing to help out

8)never sanded the hole edges or used a dremil, to this day the hole I drilled does not leak

I appreciate the offer to come and help, maybe just cold beer and skiing instead of working when you come through. The reason I drought up the sand paper or dremal is to bevel the edge of the hole so that it doesn't crack the gel coat. Maybe I'm confusing the process for installing a tower vs a thru hull fitting.

I think I might have it I just need to grow a pair and start drilling into the bottom of a perfectly good boat. Has anyone ever used a larger thru hull fitting and ran 2 pumps off of it? I would think going to like an 1 1/4 thru hull would be able to handle the flow requirements of 2 Johnson reversible pumps.

Me & E will come and drink some beers & start drillin holes in your boat. My Dad's got an ultimate set of tools.

http://youtu.be/QUwSy-w8Apw

Use painters tape from the outside on the gel coat to prevent chipping, it usually gets covered up.

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Originally Posted by chadjitsu1

Has anyone ever used a larger thru hull fitting and ran 2 pumps off of it? I would think going to like an 1 1/4 thru hull would be able to handle the flow requirements of 2 Johnson reversible pumps.

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Do you have room for a monster like that in the bilge? I noticed the pieces start getting real big real quick after you surpass 1".

Don't notice this mentioned yet. I drilled a pilot hole from the top down. Then went under the boat and drilled up into it with the hole saw. This method allowed me to double triple check placement with the small hole before committing to the big hole. If I was off a little I could move in any direction just a little and go again as long as the pilot hole stayed within the diameter of where the hole saw was going to go.

Never had to, but liked having that option in the back of my mind as I was mustering up the courage to pull the trigger.

That's what I did too and taped over the gel coat to avoid chipping. Drilled up from the bottom using the pilot.

I used the diamond hole saw for ceramic tile, i worked perfect with out and chipping of the gel coat. It made a nice smooth clean cut that was not sharp or jagged. I would recommend this for anybody who need to cut a hole in their boat!

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Originally Posted by chadjitsu1

I appreciate the offer to come and help, maybe just cold beer and skiing instead of working when you come through. The reason I drought up the sand paper or dremal is to bevel the edge of the hole so that it doesn't crack the gel coat. Maybe I'm confusing the process for installing a tower vs a thru hull fitting.

I think I might have it I just need to grow a pair and start drilling into the bottom of a perfectly good boat. Has anyone ever used a larger thru hull fitting and ran 2 pumps off of it? I would think going to like an 1 1/4 thru hull would be able to handle the flow requirements of 2 Johnson reversible pumps.

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A 1" will handle the flow rate of 2 reversible pumps, no need to go with 1.25".

how will a 1inch intake handle two reversible pumps?? Maybe when you are filling them up but it is still only a i inch hole that two pumps are fighting to push water out of. I would just put in one extra 1 inch thru hull. I spoke to wake makers last year and they recommend for each pump to have its one thru hull. when you see the kinda pressure these pumps put out you will understand why......

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when you see the kinda pressure these pumps put out you will understand why......

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Yep, see it! been doing ballast installs for 5 years now. You would actually be surprised how little pressure these types of pumps produce. Its all about flow and volume, so pressure is just a byproduct.

My advice to the OP, If I new more details about the system as a whole and how it was going to be used, I may make the suggestion of going with a dedicated t-hull for each pump. But, the question was asked and I answered it based on my experience and knowledge. Take the recommendations of those your are purchasing from.

so what you mean is that if i run two pumps off of one 1 inch t-hull that my fill and empty times will be exactly the same as 2 separate dedicated t-hulls...... I have not being doing ballast installs for five years but I don't understand how that would be possible. I just know that if you are spending the money on the reversible pump system you would want it to be efficient as possible and if you are drilling on hole, you might as well do two and do it right.

Saskie99,

I can not comment as to why the folks at Wakemakers suggested you go with individual t-hulls. I know absolutely nothing about your system design or how its used. I do not know the exact context of the conversation. Knowing Jason and Spencer, I am sure it was solid advice at the time it was given, based on your particular setup.

Lets go back and break down chadjitsu1's question about intake size.

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would think going to like an 1 1/4 thru hull would be able to handle the flow requirements of 2 Johnson reversible pumps.

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This thread started out with some questions about the actual installation, particularly drilling holes. I drew the conclusion that the OP had already designed and purchased his ballast system. Chad later asked if a 1.25" thru-hull would handle the flow of 2 reversible pumps. The answer is yes. I stated that a 1" can handle the flow of 2 reversible pumps. He did not ask about how he should configure his system. He did no ask if he should go with a single 1.25" t-hull. In fact, he didnt state what he was/is planning on going with, he simply asked about flow rate and a thru-hull size. So as they say in court, asked and answered. I did not suggest he go with a single 1", I did not suggest he go with a single 1.25". I did not make the claim that the flow rate would be equal. You seem to be making an argument against a recommendation that wasn't made and your position is based on a recommendation made to you, that was of a different context.

Unfortunately, I am pressed for time this time of the year, so I do not have the time to mock up a dual pump system using a 1" and 1.25" t-hull and measure the flow rate of the 2. But, im willing to bet that there would be a slight reduction in flow with the 1" and it would be measured in seconds, when filling or draining a typical sac. Maybe next fall when it slows up, I can do this an report back.

Ok if i decided to go with a 1 inch fitting and run 2 pumps off of it would it make that big of a difference on the flow rate. It might be worth it to me to save 3 holes in the bottom of the boat if my fill times are only going to be changed my one minute total. I am willing to save money and peace of mind to go this rout. plus in the case where I may be filling and emptying (to change sides for surfing) this might actually not affect the fill rate at all because the one pump would be feeding the other.

Ideas?

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Originally Posted by MLA

Saskie99,

I can not comment as to why the folks at Wakemakers suggested you go with individual t-hulls. I know absolutely nothing about your system design or how its used. I do not know the exact context of the conversation. Knowing Jason and Spencer, I am sure it was solid advice at the time it was given, based on your particular setup.

Lets go back and break down chadjitsu1's question about intake size.



This thread started out with some questions about the actual installation, particularly drilling holes. I drew the conclusion that the OP had already designed and purchased his ballast system. Chad later asked if a 1.25" thru-hull would handle the flow of 2 reversible pumps. The answer is yes. I stated that a 1" can handle the flow of 2 reversible pumps. He did not ask about how he should configure his system. He did no ask if he should go with a single 1.25" t-hull. In fact, he didnt state what he was/is planning on going with, he simply asked about flow rate and a thru-hull size. So as they say in court, asked and answered. I did not suggest he go with a single 1", I did not suggest he go with a single 1.25". I did not make the claim that the flow rate would be equal. You seem to be making an argument against a recommendation that wasn't made and your position is based on a recommendation made to you, that was of a different context.

Unfortunately, I am pressed for time this time of the year, so I do not have the time to mock up a dual pump system using a 1" and 1.25" t-hull and measure the flow rate of the 2. But, im willing to bet that there would be a slight reduction in flow with the 1" and it would be measured in seconds, when filling or draining a typical sac. Maybe next fall when it slows up, I can do this an report back.

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chad, Mike (MLA) knows his stuff. Just FYI, the 2009+ model year GIII systems w/ the reversible pumps have 1 thru hull per pump (i.e. 3 total thru hulls). Prior to the reversibles, a lot of guys were having sucess with a T on the intake and running 2 aerator style intake pumps.

Jusy my opinion, but you've bought the expensive part of your system with the pumps so why not just dedicate a line to each.

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Originally Posted by wolfeman131

...Jusy my opinion, but you've bought the expensive part of your system with the pumps so why not just dedicate a line to each.

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I would agree with that, as how much is the additional hose and fittings. That's what I am doing right now.

Though the equation for flow is; Flow (Q) = V*A (Velocity of the fluid x Cross-Sectional Area), so if you keep the cross sectional area, either one inch or inch and a quarter, and double the flow (Q) you will end up just doubling the fluid's velocity. This is of course ignoring the effects of fluid velocities and drag.

But like others have said, your already drilling one hole...

Its not so much a money thing as it is a Swiss cheese thing for me. I'm just nervous about it that's all. The way it looks all I would need to do is add one extra fitting if I share fittings with a T. I am going to go out and buy a diamond bit for this no matter what. I really like what I hear from saski99. I think that is going to take a lot of the trickery out of it without the worries of chipping gel coat and other things. Maybe I will set this up in the garage and actually test it to see exactly what king of flow difference I get. All I need to do is hook my new pump up to a 1 inch fitting and read the flow rates then hook up 2 pumps and see what it looks like, should be easy enough especially since I need to buy a 1 inch fitting either way right?

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Originally Posted by wolfeman131

chad, Mike (MLA) knows his stuff. Just FYI, the 2009+ model year GIII systems w/ the reversible pumps have 1 thru hull per pump (i.e. 3 total thru hulls). Prior to the reversibles, a lot of guys were having sucess with a T on the intake and running 2 aerator style intake pumps.

Jusy my opinion, but you've bought the expensive part of your system with the pumps so why not just dedicate a line to each.

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Quote:

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Originally Posted by wolfeman131

Me & E will come and drink some beers & start drillin holes in your boat. My Dad's got an ultimate set of tools.

http://youtu.be/QUwSy-w8Apw

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Yeah, I'm in Canton and we are in Cumming all the time. Hoping to move over that way soon. But if you need help Drew and I will come hang out. We have a lot of work to do to my boat anyway so really what's one more boat...


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That sounds awesome man. Let me know when you have some time. I am thinking about getting the boat out at the end of this month. I have it a a marina now on a dry slip so I need to make sure the weather isnt going to get cold enough to do any damage before I drop it in the water to get it on the trailer

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Originally Posted by E4NASH

Yeah, I'm in Canton and we are in Cumming all the time. Hoping to move over that way soon. But if you need help Drew and I will come hang out. We have a lot of work to do to my boat anyway so really what's one more boat...


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Originally Posted by wolfeman131

Prior to the reversibles, a lot of guys were having sucess with a T on the intake and running 2 aerator style intake pumps.

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I run this with two T-1200's and one side fills faster than the other, but slower in general than when running one at a time. (Basically the 1" can't handle two pumps pulling at the same time "as well".)

You could always start with the T setup, if you don't like it, add another hole+fitting+valve. Much easier to add more holes than to remove them. :p

To keep things in perspective, I'd like to point out a couple of things in regards to what Berger is experiencing. 1) the T1200 is a higher GPH pump, and 2) the T1200 is an aerator style pump and not a self-priming impeller pump. The aerator's flow is dependent upon a good supply of water into the pump body inlet. its designed to push water. The self-priming impeller pumps have the ability to draw the water into the pump at the same time its forcing it out the other side.

For a dedicated surf setup, or at least a system thats primary focus is on surfing, you can easily and most definitely use a single t-hull for the two rear sacs. 90% of the time, you will only be filling one rear sac and a belly/bow sac at a time. So the occasions are rare that both the rear sac fill pumps will be running at the same time.

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Originally Posted by MLA

So the occasions are rare that both the rear sac fill pumps will be running at the same time.

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Mike, you need to come surfing with us. Its not so rare. :)

Later tonight I will be posting the details of my ballast project...both pumps will be running for both sides.


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Check out this Video.

http://www.youtube.com/watch?v=r8oprSN59A8

Jason, very nice video! I wish you would have showed how it's nice to have another guy hold the fitting from the bottom when you tighten the nut though. Still, nice job taking the fear away for folks. Thanks for sharing this, Mike.

Looks super easy, I think I got it. Thanks for posting that video

Ok so today i had some free time and I decided to set this up and test it to see exactly what kind of flow difference I would get if I used T fittings and ran 2 pumps off of one thru hull fitting VS one thru hull fitting per pump. Below are the results of the test.

Stand alone pump (one pump and one thru hull)
Flow rate = 13.5 GPM

400 LB Bag = 48 gal = 3.5 min
650 LB Bag = 78 gal = 5 min
700 LB Bag = 84 gal = 6.2 min
1100 LB Bag = 133 gal = 10 min

2 pumps on one thru hull only one running (one pump sucks air from the other, not a good seal)
Flow Rate = 12 GPM

400 LB Bag = 48 gal = 4 min
650 LB Bag = 78 gal = 6.5 min
700 LB Bag = 84 gal = 7.5 min
1100 LB Bag = 133 gal = 11 min

Both Pumps running connected to the same thru hull fitting
Flow Rate = 10.75

400 LB Bag = 48 gal = 4.5 min
650 LB Bag = 78 gal = 7 min
700 LB Bag = 84 gal = 8.25 min
1100 LB Bag = 133 gal = 12.4 min

So my conclusion is that there is roughly a 20% +/- when running 2 mumps through the same fitting both filling and emptying. I am not sure if this has to do with the size of the thru hull fitting or if it has to do with the T fitting but it really does make a difference when setting these things up. Also one of the biggest things that surprised me was that the one pump would suck air from the other if only one was running. This also made a little bit of a difference.

So i guess the biggest question now is now much is 2.4 minutes worth to me. Is it really worth cutting 2 more holes in the bottom of the boat for that amount of time, plus the added cost of shut off ball valves and thru hull fittings. I am trying to figure that out for my own personal set up I guess. I also wonder if once water is in the line if the air sucking issue will go away, maybe the water will create a better seal around the impeller on the pump and not let this happen. I am still on the fence about the whole thing to be honest with you.

Just thought that I would share my findings with everyone, obviously its better to go with a thru hull fitting per pump but the difference is only 2.4 minutes. Also my math may be off just a little bit, I rounded my numbers FYI.

Awesome work, excellent info. If your off-side sac had a check-valve in the vent line, I bet the other side fill pump would not draw air. This would reduce your fill time and improve the flow rate. yes, a larger intake setup would improve the numbers as it would offer more flow capacity. Down side is, there is a pretty good price increase when you step up from 1" to 1.25". But, a single 1.25" will be less expensive then a pair of 1"

Thanks Chad. Been following this because I am adding a pump and two bags to my buddy's 100k boat and there's no talking him into another thru hull. He won't mind the 20% loss, he wasn't even planning on being able to run both pumps at the same time.

that is wicked that you set it up just so we all a had info on what is best for everybody's setup. 2.4 min to me is worth a hole in the boat, only bc I have two small kids and that is 2.4 min shorter that they need to wait. But for some people they may feel that it is not worth it but test is awesome and now people have legit info to make a decision on what set up is best!
Thanks again!

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Originally Posted by saskie99

that is wicked that you set it up just so we all a had info on what is best for everybody's setup. 2.4 min to me is worth a hole in the boat, only bc I have two small kids and that is 2.4 min shorter that they need to wait. But for some people they may feel that it is not worth it but test is awesome and now people have legit info to make a decision on what set up is best!
Thanks again!

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We have a short season, 2.4 minutes difference may not sound like much but over the entire season that's a lot of time wasted..I'd rather spend it surfing... :)

The one test that I meant to try out was to run one pump in the forward direction and the other in the reverse direction to see if it forced more water through the filling pump. Maybe that sounds confusing but if you have a T fitting and one pump is emptying and the other is filling then they would both be utilizing the same thru hull fitting. I would think that the pump emptying would increase the line pressure and actually feed the other pump. I am willing to bet that there wouldnt be all that much of a difference because they should be moving the same amount of water.

I am also a little nervous about the one pump that is emptying injecting air into the system and causing the flow to go to hell. I am thinking that I'm going to go with a thru hull fitting for each pump myself. Its the air issue that I am afraid of all the way around.

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Originally Posted by chadjitsu1

The one test that I meant to try out was to run one pump in the forward direction and the other in the reverse direction to see if it forced more water through the filling pump. Maybe that sounds confusing but if you have a T fitting and one pump is emptying and the other is filling then they would both be utilizing the same thru hull fitting. I would think that the pump emptying would increase the line pressure and actually feed the other pump. I am willing to bet that there wouldnt be all that much of a difference because they should be moving the same amount of water.

I am also a little nervous about the one pump that is emptying injecting air into the system and causing the flow to go to hell. I am thinking that I'm going to go with a thru hull fitting for each pump myself. Its the air issue that I am afraid of all the way around.

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Where would the air be coming from?

Cavitation from the pump..

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Also if there is any air in the bag once it gets empty then the pump would turn into an air pump instead of a water pump and inject air into the line that the other pump is drawing from.