Drilling 1" thru hull intakes

I am preparing/researching to add a couple JABSCO pumps to my ballast system. These bags used for surfing, will be filled completely seperate from the stock Malibu ballast system (MTC/Maliview). I have been doing research on the best method to drill a couple 1" holes in the bottom bilge/transmission area of the boat. Has anyone done this confirm this is correct? The system will be on a 2011 VLX.

Pick location and drill small pilot hole from inside of bilge area to target location
Place masking tape over target area on outside gelcoat area
Once under boat, drill 1" hole saw bit in reverse until gelcoat is broken thru, then switch to forward
Go very slow and make sure holesaw bit is level on surface
Once thru, lightly sand inside of hole to prevent any cracking of gelcoat
3M 4200 inside rim of hole and goop it all over when installing thru hull intake

I have attached a youtube of someone doing this, wakemakers says its pretty straight forward and nothing too crazy. They have installed many of these intakes on a variety of boats with no long term problems.

PART 1:
http://www.youtube.com/watch?v=2_A5sHIw66Y

PART 2:
http://www.youtube.com/watch?v=b0Bf82gwx-o&NR=1

If anyone here has done this and recommends any special bits, techniques, etc... I am going to plan on using the same bit in the video a 1" holesaw bi-metal bit.

Thanks for any input or recommendations.

Don't get it wrong. Thats all I got sorry.

Choose the holesaw size based on the OD of the thru-hull. Measure to confirm, as you dont want the hole any larger then needed. It never hurts to drill a test hole in some plywood first, just to see how the thru-hull fits.

I like to dry-fit all the plumbing in the bilge before drilling. This way I know I have no clearance issues with pumps, fittings, hose, etc.

For the sealer, lay a uniform bead of sealer around the flange of the thru-hull and then another around the hole on the bilge side. Let the clamping force of the thru-hull squeeze out the sealer as it tightens up. More is not always better when using sealers.

http://www.northerntool.com/shop/too...8193_200328193

One in the bilge, one on the outside. Much less risky than to drill a pilot hole. It works like a champ. Like what was said above, make sure you have your plumbing figured out for angles and rotation for installation before you do the deed. That would be a terrible way to find out you were just a little bit off with your calculations

Originally Posted by chpthril

Choose the holesaw size based on the OD of the thru-hull. Measure to confirm, as you dont want the hole any larger then needed. It never hurts to drill a test hole in some plywood first, just to see how the thru-hull fits.

I like to dry-fit all the plumbing in the bilge before drilling. This way I know I have no clearance issues with pumps, fittings, hose, etc.

For the sealer, lay a uniform bead of sealer around the flange of the thru-hull and then another around the hole on the bilge side. Let the clamping force of the thru-hull squeeze out the sealer as it tightens up. More is not always better when using sealers.

Thats a great idea with the plywood, and I will definitely dry fit everything for clearance issues.

I did something similar to this on my '08 Supra when I redesigned the ballast system. Although the hole was already drilled from the factory. I did have to take the old thru hull out and install a different one, never had any problems with leakage or gelcoat issues.

Thanks again for the feedback.

If the hole you drill is tight, you can adjust it easily with a flapper sanding wheel on the drill after. That way you get a snug fit.

Already Travis??? Do you even have the new one yet????

Just kidding,
Todd


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just do it

I never swich to forward when drilling thru gell. the teeth on those hole saw can easily chip/crack the gel IMO. I stay reversed the whole time. I also drill a hole thru plywood first to make sure everythign fits perfect.

After being on the fence about going with the JABSCO or aerator pumps I have decided to go with the new RULE Tournament 1100's (aerator). The nice option about these is I will be able to tap off the existing 3/4" vdrive area drain plug hole that comes stock from Malibu. The new 1100's are putting out an impressive 18.3 GPM, which is much faster than the JABSCOs. I am going run a "T" off the intake and have a seperate pump for each bag to fill. The 1100's will also be on each bag for draining. Will be installing seperate fill/drain toggles for each pump, the system will be completely seperate from the stock MLS. Which will allow me to fill the hard tanks at the same time as the 750 surf bags.

According to wakemakers you can get 2000 GPH from a 3/4" intake, I will only be running one pump for filling at a time at 1100 GPH so it should not be a problem. The bags will only be used for surfing purposes. For draining and venting I will just "Y" into the existing gunwall thru hulls that were installed by Malibu. If all goes to plan, the 1100's will fill a 750 lb bag up in 5 minutes, which is pretty impressive.

Anyway, no need for drilling at this point, which I am pretty cool with at this point. Thinking about drilling into a brand new boat is a little nerve racking.

Thanks for all the feedback, always appreciated.

Originally Posted by tgoin

Already Travis??? Do you even have the new one yet????

Just kidding,
Todd


Sent from my iPhone using Tapatalk

I know Todd, you know me.... planning already, wanted to have all the parts here so I can get right to work. Boat will not be in until late March, spray date is March 3rd. Not that I am counting days or anything

Use a carbide bit hole saw to cut through the gel coat. This way, it will not chip at all. I used this bit when I had to upgrade my ballast system. Works like a charm. I think that I bought the bit at Home Depot.

X2 on what tazz3069 says,the square teeth don't grab and chip the gel like the saw tooth ones. Here's a link for an example of this hole saw http://www.mkmorse.com/products/index.aspx?product=18

Here is a few picture





Make sure you use a quality marine grade silicone sealant.

Here's another little trick that I've used in the past to know precisely where your intake will be (you don't want to end up drilling thru to a non-flat surface!):

If there's an existing drain hole near by, get an old wire coat hanger and bend it into a squashed 'C'. Bend the tips so that they point at each other and make the overall length of the "C" the distance between your existing hole and the new one. Now just stick the bottom half of the "C" thru the existing hole. Point the top half where you'll drill the hole and the bottom half will point wherer the hole will come out.

I hope this makes sense. It's super easy, but hard to describe.