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Discussion Starter · #1 ·
As I look towards spring and start to get the new to me boat ready I noticed that my airmar thru hull transducer has a flapper on the thru hull when I pull it so an extra plug can be quickly swapped into it so the knotmeter paddle wheels can be cleaned. Great, seems like a great idea.

However, my flapper is cracked and is missing about 1/4 to 1/3 of the plastic flap. I assume the PO left it installed with some water stuck in there during the cold winters we get on lake michigan and the water expanded when it turned to ice and cracked the flap.

My question is: will this missing portion warrant me unable to do the swap if the paddle wheel needs to be cleaned? I know they also sell a similar type without this flapper valve but I'm not sure if that is meant for a retractable unit as you'd get much more water ingress without the flapper. Do paddle wheels need to ve cleaned very often in the cool fresh water of lake michigan?

Weighing my options whether I should replace the thru hole before I launch or not (in between all of my other tasks I have to do before launch of course...ha!) Another option might be to just let it ride this year and if the wheel gums up I can go without a speed indicator until next year.

Any advice greatly appreciated!
 

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I found that in salt water LIS the paddle wheel fouls VERY (too) quickly. Best practice is to insert only when underway... so the flay anti valve is a good idea... you still have water to clean up... but it's manageable.
 

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Boat owners near me only talk about pulling the sensor before they get hauled out in the fall so the slings don't damage it. I'm on Lake Michigan as well. I don't think it's as much an issue here. I could be wrong though. I don't have personal experience. I've just listened to the stories of others intentionally opening a 1-1/2" hole in their boat.
 

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It's not uncommon for the flap stick a bit open, from being fouled anyway, so I wouldn't rush to change it. Think about it next time you're hauled, if it lets too much water in. I think you need to break the seal and replace the whole fixture, so I'd probably avoid it, unless truly necessary.

Have you ever done this swap in the water? First time gets your heart racing, but it's like seeing blood. Looks far worse that it is. Have the opposite plug in your other hand, as you pull one out. It's not going to be pushed back like a fire hose, so focus on getting it seated and don't worry about cranking the retainer ring, until you have it snuggly in. Good idea to lubricate the orings with silicon grease too, once or twice per year.

Think about cleaning the paddle wheel and applying some MDR tranducer paint on it. It extends the fouling notably. Nothing better than actually moving regularly too.

In RI, I can get away with leaving the transducer in (with paint on it), until late June or early July, as the water is mostly cold and clear. Once it warms, I need to pull it weekly. The transducer paint allows me to sometimes get away with bi-weekly, if I've been sailing enough.
 

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Hello,

I guess I don't understand your question. I have had units with the flapper and units without. When I go to clean my speed paddle wheel I remove the transducer and insert a blank plug (or wooden plug on one of my older boats). The only difference between the flapper and no flapper is how much water comes into the boat. With the flapper I get a few ounces of water in the boat. Without the flapper I would get more water, but less than a gallon. The main difference (to me) is that with the flapper I can take my time inserting the plug. Without the flapper I would be ready to QUICKLY put the plug in.

I would not go through the trouble of changing anything just because of the flapper. To be honest, my speed fouls quickly and I only clean it if I'm going on a long trip or have an important race. Otherwise I ignore it. The speed display of 0 bothers me, but not enough to make me clean the wheel.

Barry
 

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Discussion Starter · #6 ·
Appreciate everyone's reply!

I was basically looking to tap the knowledge bank of the sailnet community as I've never owned my own boat and never had to perform the change out.

Definitely seemed like it would he a scary thing to do the first time. I mean who wants to purposely open up a hole in their boat. I figured the flap was 100% necessary but it sounds like it is just a nice to have feature.

Base of the responses it sounds like if im quick I shouldn't have any issues even if the flap is slightly cracked.

The antifouling paint sounds like a great idea too. I'll just buy some spare o-rings for the transducer and plug and get ready to sail!

Thanks again!
 

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The antifouling paint sounds like a great idea too. I'll just buy some spare o-rings for the transducer and plug and get ready to sail!
Just to be clear. Tranducer paint, not standard bottom anti-fouling. You probably don't need spare o-rings, but they can't hurt. The silicon grease keeps them flexible, but also substantially aids the seal. It's a common hack to seal up any gasket drip, until you get a new one. In this case, it also help get the plug all the way in more easily.
 
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The first few times you swap the transducer in and out of the boat without the flapper might be alarming, as you see a small water spout spewing water into your boat. Test and make sure your bilge is functioning before you make the swap happen. Not that you will sink so much as you don't want that water sitting in your bilge any longer than it has to. Also, be as patient as you can, make sure when you begin tightening the transducer that you do have it lined up correctly and that you are not tearing the top threads simply because it was misaligned and you didn't notice it. Mine is not in a particularly friendly location, so I am forced to come at it a little awkwardly.
 

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Not that you will sink so much as you don't want that water sitting in your bilge any longer than it has to.
Good point.

On my long range to-do list (the one that only gets done, when I get an inspiration caused by necessity), I plan to epoxy a box of G10 or similar fiberglass board around my speed thru hull, to capture the water ingress. It has a way to go to get to our bilge pump and some inevitably gets caught up in the corners of ribs and stringers that lie below the limber holes.

Installing the wheel is not an issue, as we'll be going out sailing and the heeling back and forth manages to move the seawater around and mostly get it to the pump. It's putting the plug in, where the boat will inevitably sit for several days that the issue. Ours flows through some hard to access bilge area, so others may find this less cumbersome. I will sometimes dam it up with towels to capture the majority or reach under the sole, with our small portable shop vac to clean it up.

All I'd need to do is create a box around it a few inches tall and then use a sponge or the shop vac in one easily access area to clean it up.
 
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