Raymarine ST-40 Speed Question

[Carl Thunberg]

I just purchased an ST-40 bi-data depth/speed unit with both transducers. The speed log has the usual paddle wheel, but it's removable. When you leave the boat for a week or so, they recommend removing the speed log and inserting a plug in its place, so the paddle wheel doesn't get fouled with marine growth. I practiced switching the speed log with the plug several times last night, and it seems fairly straightforward in the comfort of my living room.

But I can't get over my reluctance to remove that which is holding the ocean out You can imagine the look my wife gave me when I explained this process to her. Speed by GPS is looking better all the time. Does anyone out there have the same, or similar, unit and can anyone tell me how much water I should expect to leak (gush?) into the boat during this switch?

[Russell]

But I can't get over my reluctance to remove that which is holding the ocean out You can imagine the look my wife gave me when I explained this process to her. Speed by GPS is looking better all the time. Does anyone out there have the same, or similar, unit and can anyone tell me how much water I should expect to leak (gush?) into the boat during this switch?

I have pulled it out a few times to clean it, but generally dont bother, as it refouls pretty quickly anyways. The only thing I have found handy about the knot meter is being able to use it to judge current better when compared to SOG from GPS.

And yes, a lot of water does come gushing in, be ready with towels and prepare to get fairly wet yourself. It does give a fair idea of how quick a boat can sink with a failed seacock!

[darmoose]

carl,

i understand your point. i have had a log in mystic rose for the past six years, and even tho i continuosly tell myself that i am going out there and pull that unit out and put in the plug to clean it......... i havent yet.

i would rather dive under the boat and clean the wheel from there. i did witness once a mechanic pulled it out, and replaced it. he stuffed a rag into the hole while he messed with the unit.

my greatest fear is that for some reason, i wouldnt be able to get either the plug or the unit back into the hole.....oh my god.

i still say i'm gonna do it.....someday.

darrell
mystic rose

[Boyd]

Hi Guys:

I just replaced my old DataMarine units with the Raytheon like yours. The transducer housing has a flap in it that is supposed to hold back the ocean while you swap it out. I havent tried it yet but will without hesitation. I swapped out the old style transducer for cleaning many times on this and my old boat.

The effect of a hole that big about 2 feet below the water line is .....like a fire hose. Just be organized and quick. The amount of water is easily handled by your bilge pump. The new style with a flap should be very managable.

I used to telll guests when they asked about the water.. "Oh no problem we were just sinking there for a minute."

Boyd
s/v Tern
CD30 MkII
Fort Lauderdale, Fla.

[Anthony P. Jeske]

Hi:
I never leave my paddle impeller in when I'm not sailing. On my current boat, a CD-28, the impeller is located in the bilge, it's easy to get to it, located right below the access panel in the sole. Yes, it's a little scary at first, but that adrenaline rush goes away after you've swapped it a few times. There's an orientation groove added by the PO on the impeller and on the plug. My last boat, a CD-25D, had one of the flappy valve thingys on the thru hull which really cut down on the water intrusion. That's a great feature.
Good Luck,
Tony Jeske
CD-28 #365
NO REGRETS
San Diego

[Russell]

The effect of a hole that big about 2 feet below the water line is .....like a fire hose. Just be organized and quick. The amount of water is easily handled by your bilge pump. The new style with a flap should be very managable.

I dont find the flap does much, but perhaps my flap has been jammed or broken, because the water flow is certainly full force.

[Dean Abramson]

Carl,

I wouldn't do it. Way too much excitement for me, and some small chance of disaster. And honestly, do you really think you would continue to do this routine on a regular basis?

I had two tricks on my 25D for this. When I first noticed it was stuck, I would motor as fast as I could in reverse (best if you have a little room around you somewhere!!); half the time, this freed it, and it would be fine for a long time. The other thing is I found I could hang off of the toe rail and free it with my feet. My sense is that it is not growth per se so much that fouls it, as it is a small piece of something getting stuck in there. And once it is free, you are good to go for quite a while. At least here in cold Maine waters like you and I are.

It would be easy enough to do with a long-handled brush. Do some measuring when the boat is on the hard, so you can be precise about where to scrub; mark the handle of the brush at, say, the bootstripe, and find a spot which is exactly vertically above the paddle wheel to orient yourself by.

Then there is diving, but I try to avoid that. Even though I have two GPSs, I like knowing speed through the water, as that discounts current, and gives me the best read on how my sail trim tweaks are working.

Good luck! Another beautiful weather day in the northeast...

Dean

[Neil Gordon]

It's a fairly straightforward swap. I put a large sponge into the locker where the hole is and I don't get any more water than can be absorbed easily. The flapper keeps most of the ocean on the outside where it belongs.

Get the plug lined up and ready to go so you pull one unit and replace it with the other. It only takes a few seconds. If you can, have someone with you who can scream for help while you cover the hole with your hand, at least until you become more comfy with the process. Oh... a wood plug nearby will provide added assurance.

[Carl Thunberg]

Thanks for all your input and experience. I'm not sure I feel any better, though .

[Marc Theriault]

Carl,

I did it many times on my Alberg 22 without any problem. Like Neil said keep a sponge near you. I will add that i never bother to remove the transducer at the end of the day but i did remove it only for cleaning the wheel or at the end of the season.

Marc

[Dean Abramson]

Carl,

I have had really good luck with my speed impellers with no in-season cleaning. I have had entire seasons where all I had to do was motor in reverse once or twice. Sometimes it would be stuck for the first few minutes after I left the dock, but would then free itself.

I wouldn't fix it until it's broken. I would just launch the boat with the impeller in, and see how it goes. On my 25D, I never once removed that transducer, ever. I am not sure how much an issue this is in our cold waters, particularly on boats that are used regularly. If by chance you moor in a river, the current may keep it (turning and) clean. My brother-in-law and I once stayed at a mooring in a river, and at ebb tide if we flipped on the juice, we were doing four knots!

Dean

[Carl Thunberg]

Hey Guys,

I've decided I'll just be present when they launch me some time in May. Before I'm out of the slings, I'll practice the switch a couple times. If there's a problem, they can yank me back out. If it's as easy as Boyd, Anthony, and Neil say it is, then I'll at least not hesitate to do it again if the scrub brush doesn't do the trick. I really don't think I'll be diving in, though. This water is wicked cold! And Dean, yes, I'm in the Piscataqua River with some pretty swift current which should help a lot. Thanks for all your help.

Carl

[Dalton]

I pull mine all the time. I spread a towel around the area and hold it around the housing and have gotten pretty good at doing it quickly. The flap works pretty well but there is still some inflow. The towel catches a lot and I just wipe the area up thoroughly afterwards. Another trick I've learned is sometimes when it stops spinning I loosen the locknut slightly and turn the transducer 180 degrees a few times and that frees it up sometimes. I also use tranducer anti fouling paint on it and that helps for a while.