How to Properly Add a Thru Hull

[MarkD]

Boat is a 2008 185 Sport with 4.3L engine.

I am planning to add a second bilge pump and will need to make a hole in the side for a thru hull fitting. My question is, what is the proper tool and/or procedure for doing this?

In addition, would I add the second thru hull on the opposite side to the existing one or keep everything on the same side?

Thanks

 

[Go Aweigh2452]

Boat is a 2008 185 Sport with 4.3L engine.

I am planning to add a second bilge pump and will need to make a hole in the side for a thru hull fitting. My question is, what is the proper tool and/or procedure for doing this?

In addition, would I add the second thru hull on the opposite side to the existing one or keep everything on the same side?

Thanks

Mark, you can add the bilge thru hull to either side. I'm sure it would look good next to the existing one. Best way to add is to get a hole saw the size of the outer diameter of the thru hull. Its OK if it is a tad bigger hole than the thru hull.

Place some masking or painter tape where you intend to cut through on the outside of the hull. The tape will minimize the fiberglass from chipping too much. The flange on the thru hull will cover any chips anyway... Mark and slowing drill through. The hull is less than 1/2 thick and maybe as thin as 1/4 inch.

Once through the hull, remove the tape and insert the thru hull to check for fit.

Wipe some 3M 5200 on the new cut edge to ensure good sealage, add a bead of 5200 to the inside of the flange and push in the hole. From the inside, just tighten the nut. You may need a partner to hold the thru hull in case it spins too much. you don;t have to tighten too much. The 5200 wil seal very well.

I would suggest at this time to change over to stainless steel vice the plastic thru hulls since you are redoing one anyway. This way you'll have nice bling and two matching thru hulls. ALso make sure the hose between the bilge and the thru hull is not in the way of being stepped on or near the belts or heat source... Attwood makes some nice 316 stainless at firstchoicemarine.com

Let the 5200 set for the day and then use some 5200 to seal the hose to the bilge pump and thru hull. Use a stainless steel clamp to secure the hose at both ends.

The excess 5200 can be wiped off the flange as it sets or cut it off after it sets. Use some acetone to remove if it dries hard too fast.

I just added/replaced two plastic scuppers last week...

Old verses new... plastic out, stainless in...

 

[MarkD]

Thanks for the details Doug! much appreciated. Does the hole saw have to be any specific type or just a general purpose one?

As far as the location, I have to see what side is more aesthetically pleasing. I was actually surprised that the existing thru hull is already stainless. I assume its 316, but am not 100%. what surprises me more was the fact that my 37 is just plastic. how cheap is that!!! that was the early 90's for ya... they cheaped out on some things to save a few bucks.

 

[wingless]

It wouldn't hurt to seal the bore of the hole w/ West System epoxy. The epoxy protect the fiberglass from water intrusion when the 5200 fails.

 

[MarkD]

yeah, i actually purchased some of the 2 part epoxy in anticipation of that. i am guessing the boat has a cored upper so the epoxy sealing will definately need to be done.

 

[Tail Chaser 661]

I would run your bilge hose where it is the most clean looking or out of the way. Making the boat easyer to work on.

You might consider going to a bigger pump if you have room.
A 1100 gph pump uses like 1 1/8 in bilge hose if I remember right. The height was like 1 in taller then a 500gph pump.

 

[Tail Chaser 661]

Mark, you can add the bilge thru hull to either side. I'm sure it would look good next to the existing one. Best way to add is to get a hole saw the size of the outer diameter of the thru hull. Its OK if it is a tad bigger hole than the thru hull.

Place some masking or painter tape where you intend to cut through on the outside of the hull. The tape will minimize the fiberglass from chipping too much. The flange on the thru hull will cover any chips anyway... Mark and slowing drill through. The hull is less than 1/2 thick and maybe as thin as 1/4 inch.

Once through the hull, remove the tape and insert the thru hull to check for fit.

Wipe some 3M 5200 on the new cut edge to ensure good sealage, add a bead of 5200 to the inside of the flange and push in the hole. From the inside, just tighten the nut. You may need a partner to hold the thru hull in case it spins too much. you don;t have to tighten too much. The 5200 wil seal very well.

I would suggest at this time to change over to stainless steel vice the plastic thru hulls since you are redoing one anyway. This way you'll have nice bling and two matching thru hulls. ALso make sure the hose between the bilge and the thru hull is not in the way of being stepped on or near the belts or heat source... Attwood makes some nice 316 stainless at firstchoicemarine.com

Let the 5200 set for the day and then use some 5200 to seal the hose to the bilge pump and thru hull. Use a stainless steel clamp to secure the hose at both ends.

The excess 5200 can be wiped off the flange as it sets or cut it off after it sets. Use some acetone to remove if it dries hard too fast.

I just added/replaced two plastic scuppers last week...

Old verses new... plastic out, stainless in...

Those stainless thru hulls sure are clean/quality looking.
Every time I look at my 24 yr old plastic ones.
I get curious how brittle they may have become.

 

[kpetry]

Go Aweigh - Would the procedure be the same if the new thru-hull is below the waterline? I need to add a forward anchor washdown, and the best solution for supply is a new thru-hull. I'm worried about water intrusion though. Would the West System be a better option in the below water case?

 

[tginz]

I only see the West System as an advantage if you have a cored hull. I just replaced my drain plug and it was solid fiberglass at that point in the transom. I buttered up the hole, fitting, etc with 5200 and put it back in. I saw no advantage to "westing" anything.... For a cored hull I would recommend drilling a little larger and sealing the core with West System prior to hull installation and absolutely do this for below the waterline applications.

tginz

 

[MarkD]

Tailchaser... you read my mind about the 1100GPH pump. In fact i plan on getting the Rule-Mate 1100 which has the built in float switch. I can keep it uncluttered down there with this type of setup as opposed to the separate switch. Granted, if it fails i will need to replace the whole thing. Oh well. And yes, it was a 1 1/8" hose.

kpetry...you dilema is diffferent. an underwater fitting should be bronze and tied into the bonding system of the boat (that green wire). If it were mine, I would use a west system (or similar) epoxy to seal the hole once cut and then apply 5200 to seal it... 5200 is rated for underwater use from what i have read.

 

[Skuza]

For routing I would first examine ease of routing in the bilge, then aesthetics. Just because it looks good doesn't mean it will work or be worth the routing in the bilge.
I would say to epoxy the hole no matter what. I know this is mandatory for a cored hull but even on a solid hull why not just play it safe. That way if the 5200 fails and does leak one day at least you know that the fiberglass is sealed. If it does leak also you will just have to redo the seal and not have to lay awake at night wondering if any water wicked into the fiberglass. Epoxying is going to add a day to the project and thats probably why most don't want to bother. Also epoxying may shrink the diameter of the hole if you cut it for an exact fit so keep that in mind.
I have heard about the possibility of plastic thru hulls cracking off due to age too which makes you want to upgrade to stainless ones. Think of the leverage that is on some of them with how hard those hoses are.