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Old 24-02-2015, 21:31   #1
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Making a new GPS compatible with an old boat

I recently purchased a 1985 Catalina 25 as a first boat, and I'm realizing now I know very little about the electronics on this boat, specifically the GPS. Any guidance would be much appreciated.

The boat came with an old GPS unit (which appears to be broken) mounted to the right of the companionway. I'd like to replace it with a functioning unit, but I'm not sure where to start. It was suggested I look into something like a Garmin 441, but even just this model includes options between a 441 and 441s. Seems like the S model comes with a sounder. Can I get by without the sounder for depth?

There's also the option to get it with or without a transducer. Won't the model with the sounder need a transducer to function properly? I've seen a black wire on board labeled "transducer cable" but will this old cable be compatible with a new GPS?

What's the best way to proceed here? And what other information am I missing so I can make an informed decision here? Again, any help would be fantastic!
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Old 25-02-2015, 02:31   #2
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Re: Making a new GPS compatible with an old boat

On a 25 foot boat of unknown pedigree I would keep it simple.

- Remove the old crappy gps and any wiring you can
- Use your iPhone or iPad with Navionics for GPS for now - if you are worried about water get a rhino case or something

The Garmin 441 at around $600 is overkill IMO. Save your money for the stuff you are gonna need on a new to you boat.

- Buy a fish finder for less than $100 with transom mount transducer - saves you messing around with a haulout, through hulls etc. http://www.amazon.com/Lowrance-000-1...ds=fish+finder
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Old 25-02-2015, 06:18   #3
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Re: Making a new GPS compatible with an old boat

Thanks for the reply. I was considering going the tablet/Navionics route, but had pushed that to the side after reading that the screens washed out too easily in bright sunlight. Are those concerns overblown? Another consideration is that I don't currently own an iPad (or tablet) although I do have a Samsung Galaxy S5 as a smartphone. So either I use the phone and it's 5 inch screen or I buy ... something... either a GPS or a tablet.

I hadn't thought of a simply fish finder for depth. But where to mount that so it's visible in the cockpit?
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Old 25-02-2015, 06:26   #4
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Re: Making a new GPS compatible with an old boat

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...the screens washed out too easily in bright sunlight. Are those concerns overblown? Another consideration is that I don't currently own an iPad (or tablet) although I do have a Samsung Galaxy S5...
Use your phone. I would not buy a tablet JUST for use on your boat. If you have other reasons to want a tablet, great, use it for navigation also. But buying one JUST for that purpose... I'm not seeing it.

As for the screen washing out in sunlight, take a look at your phone. It sometimes washes out pretty badly, doesn't it? Well, tablets are--generally speaking--not any better (some are worse). If that worries you then I would get a simple handheld; maybe one of the Garmin 78 models.

Good luck.
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Old 25-02-2015, 06:52   #5
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Re: Making a new GPS compatible with an old boat

Some more options:

Our first GPS was a Garmin etrek vista handheld bought on ebay for around $100. Easy to read in sunlight, waterproof and durable, and very basic chart capability.

Our current GPS is an old Lowrance handheld I got at a flea market for $15. It's in a holder and I wired it to the boat 12v. It even has NMEA0183 out which will go into my DSC VHF.
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Old 25-02-2015, 07:06   #6
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Re: Making a new GPS compatible with an old boat

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Originally Posted by nickfox45 View Post
Thanks for the reply. I was considering going the tablet/Navionics route, but had pushed that to the side after reading that the screens washed out too easily in bright sunlight. Are those concerns overblown? Another consideration is that I don't currently own an iPad (or tablet) although I do have a Samsung Galaxy S5 as a smartphone. So either I use the phone and it's 5 inch screen or I buy ... something... either a GPS or a tablet.

I hadn't thought of a simply fish finder for depth. But where to mount that so it's visible in the cockpit?
Check the Samsung site for Navionics. The Garmin 76c is also a good choice but pricey - You are almost at Ipad cost (basic iPad). Anyway there are lots of choices cheaper than a full blown plotter.

As for the depth - where is the current one mounted? If you don't have a current one, it is a good add. You can have a look on Amazon - Aside from the Lowrance I linked there are several Hummingbird "in dash" units you can look at.
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Old 25-02-2015, 07:30   #7
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Re: Making a new GPS compatible with an old boat

It's unlikely you could use the old transducer with the new plotter. I would install the Garmin plotter with the largest screen you can afford that also comes with a depth sounder. One transducer option mounts to the inside of the bilge and shoots the signal through the hull without any hole in the hull. If your hull is solid fiberglass this will work, it's what I have.

Knowing how deep the water is is pretty important if you travel where it's shallow.
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Old 25-02-2015, 07:34   #8
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Re: Making a new GPS compatible with an old boat

The depth meter is critical, so I'd be tempted to get a garmin with a through-hull transducer, unless you're planning on hauling the boat sometime soon for some other reason.
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Old 25-02-2015, 10:23   #9
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Re: Making a new GPS compatible with an old boat

Yep, the cheap GPS/fishfinder is the way to go.
Learn to enter waypoints and route the new transducer cable where the old one went through.
Works fine on my MacGregor

For a chart plotter I bring my laptop with me. A USB GPS dongle and Open CPN and it all works great.
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Old 25-02-2015, 11:20   #10
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Re: Making a new GPS compatible with an old boat

Thanks so much for all the suggestions. Just last night I was thinking I was locked into buying a $600-700 unit and I wasn't even sure if that was what I needed - now I have some options and *think* I understand what I need.

After reading everything I'm leaning towards starting out with a handheld GPS and adding on the depth finder (which I agree is essential). I figure if the handheld doesn't meet my needs a few months or a season from now, it'll be a great backup when I buy a dedicated unit.

I also really like the idea of the USB dongle and laptop combo. I can keep that in the cabin to plan longer routes or get the big picture view.

So to clarify on the depth finder: that's the unit that'll need the transducer, correct? And I can either transom-mount that (as Ex-Calif suggested) or run it where the old one was? The boat is currently on the hard, so I have options as far as install goes.
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Old 25-02-2015, 11:33   #11
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Re: Making a new GPS compatible with an old boat

A Garmin 441 can be had for under $400 new, less used. I would sail without a depth sounder, but never without a chart plotter like the 441. A depth sounder tells you when you have run aground; a chart plotter not only shows you the depth under your boat but more importantly in front of it as well. Inasmuch as you are from Maryland, I presume you sail the Chesapeake. One of the great joys of sailing the Chesapeake is the literally hundreds of navigable rivers, creeks and inlets. However, the 6 foot contours on virtually all of them wiggle like a snake. If you don't have a chart plotter you are pretty well limited to navigating from marker to marker. If they truly have real chart plotter apps for cell phones you could skip all the other electronics and just sail with that.
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Old 25-02-2015, 11:36   #12
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Re: Making a new GPS compatible with an old boat

I have three GPS units on my boat, a 10" display, a 5" display at the helm, and an old backup unit also at the pedestal.

In the Chesapeake, I use my iPhone with Navionics 99% of the time. It's always in my pocket, the charts are always current, and the interface is for the most part easier to use than any chart plotter that is not touchscreen. That said, it lacks the more sophisticated chart plotting functions of a dedicated unit. But that's largely irrelevant on the Bay.

As for depth, with 4' draft you can probably get away without the depth sounder, depending on where you are on the Bay and where you go. The charts are generally accurate, despite the fact that most of the Bay outside the channels has not been surveyed since before WWII. You will likely run into infamous "Chesapeake humps" now and then, but the depth sounder will only serve to confirm that yes, you have actually run aground.

The only sailors on the Bay I know that pay much attention to their sounders are those with a 6' draft or over. You could get away without the sounder for the time being and see how it goes and how often you end up going aground. After all, there are two kinds of sailors on the Bay; those who have gone aground and those who are lying.
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Old 25-02-2015, 12:22   #13
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Re: Making a new GPS compatible with an old boat

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......... A depth sounder tells you when you have run aground; ..............
No, that sudden stop tells you when you have run aground. A depth sounder, especially one with a settable alarm tells you when you are getting close to running aground.

I'm nor discounting the value of a chart plotter, I wouldn't leave the dock without both, but charts go out of date and bottom conditions change, sometimes suddenly (think big storms).

So, I set my depth sounder alarm to a couple feet deeper than my draft and follow my chart plotter but sometimes the alarm sounds and I know to slow down or stop and figure out what is going on.
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Old 25-02-2015, 13:05   #14
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Re: Making a new GPS compatible with an old boat

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No, that sudden stop tells you when you have run aground. A depth sounder, especially one with a settable alarm tells you when you are getting close to running aground.

So, I set my depth sounder alarm to a couple feet deeper than my draft and follow my chart plotter but sometimes the alarm sounds and I know to slow down or stop and figure out what is going on.
I've heard that before; but it assumes that the bottom contours are all fairly similar--which they aren't. In some places you hit 10 feet a mile out from 6 feet; in other places you hit 10 feet 6 feet out from 6 feet--it just doesn't work.
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Old 25-02-2015, 13:58   #15
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Re: Making a new GPS compatible with an old boat

I used a TV bracket in the companionway to mount my sonar on, where I could easily swing it into the cabin or swing it outward for viewing from the cockpit.
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