Preventing growth on a thru-hull speedo

Ted · Nov 28, 2015

There is an anti fouling transducer paint for that purpose. http://shop.sailboatowners.com/prod.php?12928 You can also use any waterbased bottom paint. Most speed transducers can be removed from within the boat. Some have a "trap door" which helps slow the ingress of water. once the transducer is removed. It gives you some time to set the plug before your bilge pump starts pumping and panic sets in.

kloudie1 · Nov 28, 2015

I tried that and had no luck.. I also tried "Boudreaux's Butt Paste" for its high zinc content..
(http://www.buttpaste.com/products/maximum-strength-butt-paste) Pretty much the same as Desitin that you'll hear works for some folks. The ablative antifouling kept jamming the paddlewheel.. The Butt Paste zinc depleted very quickly because of the copper bottom paint, I'd guess.. Pulling it and cleaning seems to work best. Boat is in water year 'round so no other way to clean it.

Kings Gambit · Nov 28, 2015

Rodd said:
Wondered if anyone has a recommendation on how best to prevent fouling of the impellor blades on a plastic thru hull impellor. Seems these blades always foul and necessitate my diving and scraping the junk off to allow the blades to spin freely. would regular antifouling paint work on this?

Rodd

Isn't there a "trap door" that allows you to pull the speed log transducer? Pull it out; put in the plug, then soak the transducer/impeller in vinegar for a few hours after which you should be able to nearly wipe off the encrusting material, etc. Pull it each time leaving the boat slip-bound for any extended time, etc.

Brian D · Nov 28, 2015

The only prevention that I have found is as mentioned; pull the transducer. I have tried the Desitin stuff and it did not work. I haven't tried paint yet, but I am sure it will not work either. So, pulling and soaking in vinegar got my paddles clean. Unfortunately I do not have a trap door so when the plug gets pulled, about a half gallon of water comes into the boat.

Stu Jackson · Nov 28, 2015

Brian D said:
The only prevention that I have found is

to use the boat more often!

Stu Jackson · Nov 28, 2015

Rodd, I had the same issue. Fear is a helluva motivator. I finally started doing it and got good at it. You have to have reasonable access and figure out what works, like something as easy as "what had to use to remove and which one to use to plug it or replace it."

Like this:

I used to take it out with my right hand and try to get the plug in with my left. I'm right handed. I found, finally, that if I removed with my left (easy, just pull up!) I had a better shot at getting it back in with my right hand.

Once you get over the rush of water, which is all of less than a gallon, it's easy. I surround the area with a towel.

Good luck.

njlarry · Nov 28, 2015

I have taken a different tack and would like to know others opinion. I do not use the speedo, I use the GPS speed instead. Am I missing something? My speedo does not have a trap door and being 30 plus years old, I think constant removal for cleaning is asking for a serious leak. I just don't feel comfortable with a plastic plug in a large hole below the waterline so plan to glass it up.

shemandr · Nov 28, 2015

The best way I found is to put the blank in while not using the boat. The speedo doesn't accumulate growth sitting in the bilge. It's PITA but it works. BTW exchanging them shouldn't get more than about a quart of water in the bilge once you get good at it. "Slow is smooth and smooth is fast"

Kings Gambit · Nov 28, 2015

njlarry said:
I have taken a different tack and would like to know others opinion. I do not use the speedo, I use the GPS speed instead. Am I missing something? My speedo does not have a trap door and being 30 plus years old, I think constant removal for cleaning is asking for a serious leak. I just don't feel comfortable with a plastic plug in a large hole below the waterline so plan to glass it up.

If you have a weather station at the masthead you cannot get true wind velocity at the display if the speed log is not running. Also, you will not get the correct true wind velocity if the log is not calibrated, etc. If no masthead weather station, however, then I suppose no problem.

Stu Jackson · Nov 28, 2015

njlarry said:
I have taken a different tack and would like to know others opinion. I do not use the speedo, I use the GPS speed instead. Am I missing something?

Yes, the current.

Brian D · Nov 28, 2015

Stu Jackson said:
to use the boat more often!

Touchè - LOL

frankies56 · Nov 29, 2015

I have tried a lot of things white lithium grease anti fouling paint I think the growth laughs at that. I have found tiny crabs living inside the paddle wheels. my best is sailtrack lube. but that last about 12 weeks max and then its out again. I dont use anything but a small stainless brush and water pressure. ps I do have and extra one to put in its place when I clean it, take the good with the bad. I have learned to deal with it..

seadaddler · Nov 29, 2015

My diver told me about a trick pulling the transducer and what he did one time for
me was get one of those old red toilet plunger that he removed the handle and plugged the
hole and pushes it up against the hull over the transducer and I pulled the transducer to clean it.
My old transducer had the flapper but I changed to a newer transducer and think it was
ST 800 and it does not seem to have a flapper and the amount of water that comes in is way too much to want to want to remove it often for cleaning.
Nick

Slow lane · Nov 29, 2015

I'm with njlarry the less holes in my boat the better. Unless you race why bother.

njlarry · Nov 29, 2015

I agree the less holes the better. Speedos make VERY big holes, sometimes the largest in the whole hull. Stu and Gambit point out current and true wind are lost. What do we need either of these for? The boat only sails in apparent wind, true wind is easy to estimate if I needed to but why would I need to? My sails stay adjusted to the apparent wind. Current can help or not but I can't change it and I sail from point to point on a chart as fast I can over the bottom. Obviously I am not a racer so wonder what am I missing as there must be "some method to the madness" that I am missing. Please understand that I am asking more than suggesting.

Kings Gambit · Nov 29, 2015

If all the truth be told; then why not ask why buy any of this electronic stuff? You don't need a speed log transducer or a GPS to estimate your speed through the water or speed over the ground. You don't need a weather station to estimate your true wind or your apparent wind. You don't really need a depth transducer to find your depth. You can cruise along the coast all day long with a paper chart, a hand-held bearing compass, and a good pair of binoculars and fix your position & estimate your SOG; so you don't really need GPS or Loran C for positioning either. You don't even need a VHF, or a diesel, or an outboard, for that matter, to go sailing. You certainly don't need a Honda EU2000 generator to have a cold beer; b/c in fact--you don't even need cold beer--drink rum! With none of that stuff you don't need batteries or therefore solar panels, etc. So, clearly--"need" is an irrelevant criterion!!

njlarry · Nov 29, 2015

No cold beer!? Let's not get carried away.

Along with cold beer and a GPS chartplotter I also enjoy a depth finder. (I may be old but I'm not ancient.) In years of coastal cruising I have just never felt a concern for true wind or relative current. So I wonder how does one justify the big non-seachocked hole now that GPS gives speed over course.
Again I apologize for the hijack.

Stu Jackson · Nov 29, 2015

njlarry said:
In years of coastal cruising I have just never felt a concern for true wind or relative current.

Larry, I have no idea what "relative current" is.

But I think you mean the difference between SOG and STW.

Current is current. It's either going with me or against me. In many, many cases, like KG humorously said, we don't "need" these things. But I sail regularly in a place where the current is either on my nose or behind me. Its velocity becomes important in passage planning and ETAs and the like, and I just, well, uhm, like to know.

If folks just go out and sail around, or even just sail across a current and back (except the English Channel

), it's less of an issue. They could care less.

I like things on my boat that are installed to work. When my knotmeter stopped working last year, I investigated why it didn't, fixed it, photographed it and wrote it up for Catalina's Mainsheet magazine. I got help right here from skippers helping me with BNC connectors.

I don't believe the GPS system will ever fail, but if my two on board units do fail at the same time, my knotmeter is one very important piece of navigation instrumentation that I find is pretty essential.

Otherwise, nah, I don't need it.