PBO Project Boat Maximus will need a rewire so it's time to think about upgrading electronics. Raymarine's Richard Marsden steps onboard to talk transducers, tiller-pilots and chartplotters

Upgrading electronics on Maximus seemed like a huge leap in the first weeks of ownership. We were still discovering new leaks and lockers, choosing antifouling and scraping the bottom.

I couldn’t imagine being on the water just yet, let alone using high-tech navigation equipment.

Frankly, with everything else, the complex world of electronics was the last thing I wanted to think about on our 28ft Maxi 84. However, it looked like the PBO Project Boat might require a rewire.

While she was laid up in the yard, any mast and thru-hull fittings needed to go in now… and so it made sense to decide what would be attached to them. Fortunately, Raymarine’s expertise came to my rescue.

Flat batteries

Also, I’d booked a meeting with a marine electrician, and planned to bring along new batteries so he could test the boat’s electrical systems – something we were unable to do during the survey because the batteries were flat.

Rather than replacing the batteries with like-for-like, I suspected I’d need more power if I was going to upgrade the electronics. Again, it would help to know what I was going to need.

Article continues below…

What is an in-hull transducer?

On our PBO Project Boat Maximus we need sonar simply for measuring depth, but the advanced electronics of fish finders…

Power requirements

It was while trying to work out my power requirements that I called marine electronics specialist Raymarine. Last time I’d done any offshore cruising – on a Westerly GK24 with my dad – it was with a GPS plotter and paper charts. We didn’t have a chartplotter or even a tablet with charts downloaded.

Nor had we owned a tiller-pilot. These were all things I liked the idea of having, but right now I wanted to know how much power they consumed. I got through to Richard Marsden, Raymarine sales manager – UK & Ireland.

“Needing masses of battery power for your electronics is a bit of a myth these days,” he said. “Normally most of the power comes down to screen brightness – if you’ve got it packed right up, for example – but actually 12in screens can draw as little as 1.5A per hour.”

“For a boat your size, I’d expect you’d want a VHF, depth sounder, boat speed through the water and wind angle display – though a lot of people don’t have them on smaller boats. AIS would be nice to have. Maybe a small plotter.”

I decided to tackle power requirements another day, with some help from Ecobat and Victron, but in the meantime Richard kindly offered to come down and take a look at Maximus and suggest how we could upgrade our navigation equipment. 

In-hull and thru-hull transducer

Before stepping aboard Richard took a look at Maximus’s newly scraped hull, but fortunately it wasn’t my workmanship (and the many gouges I’d made) that caught his attention. It was the transducers.

Richard points to where the in-hull transducer must be for the depth sounder but you can’t see it from the outside. The hole above is the paddlewheel for speed.

“This is the speed,” he said, flicking the paddlewheel, a thru-hull transducer.

“But then what you have here is another transducer. It’s hidden inside the boat because it’s an in-hull transducer.

Here you can see the paddlewheel for speed (bottom) and in-hull transducer for depth (top). Ignore the grey item – it’s a cap that’s fallen in the bilge

“It pings through solid laminate. We can do something similar again. We can fit a paddlewheel speed and an in-hull transducer.”

Once inside, Richard took a look at the transducers, and sure-enough, while there had only been one hole in the hull (aside from the seacock outlets), there were two transducers – the paddlewheel for speed, which went through the hull, and the in-hull transducer, bonded to the inner hull, for measuring depth.

Wind display

“Oh, crikey!” said Richard, accidentally knocking an instrument that was hanging loose by its cable. He examined the equipment just inside of the companionway.

“You have the depth and speed – that might still work – but it looks like Heath Robinson wiring,” he said. “Currently the transducer is going into the NASA Clipper Duet and it’s wired across to the traditional wind display.”

He pointed to the cups spinning at the top of the mast. “They’re giving you the wind speed, and this is the wiring we’ve just seen running forward to the transducer. You can modernise that – either with a new cable in the rig, or you can go for a wireless option.”

Richard recommended replacing the Clipper Duet with the i70 Multifunction Instrument Display, which has digital, analogue and graphical displays of depth, speed, wind and more. It’s a 4.1in screen, with extra-large digits and a back-light for night-time, as well as sculptured rubber key-pad so you can easily switch screens in all conditions.

While I’d see myself using it primarily for depth and speed, it does have the option, if connected to an adaptor via a special cable, to talk to other instruments that use NMEA 2000 networks, or Raymarine’s own version of NMEA 2000, known as STng. So, for example, you could use the screen to check your fuel levels or as an AIS repeater.

For the wind, Richard suggested the i60 Wind Instrument, with a 30m cable and transducer, which gives wind speed and direction and shows the ‘no-go zone’, which is always useful for sailing an efficient course. After dinghy sailing – where I regularly get myself in irons – that would be a luxury!

Note: We may earn a commission when you buy through links on our site, at no extra cost to you. This doesn’t affect our editorial independence.


Traditionally, all nav equipment used to be fitted below decks, but these days people prefer to have it in the cockpit so they can see where they’re going from the helm.

A 7in chartplotter, or multifunction display (MFD), would be a good size for Maximus’s cockpit. As well as showing the course, much like a car GPS, it will give speed-over-the-ground and you can integrate radar and AIS if you want to.

“The only thing you’ve got to consider is how you sail and helm as a family,” said Richard, pointing at the space either side of the companionway where the rope pockets were fitted. “If you have someone sitting on either seat they’ll be blocking the view.”

The Raymarine 7in Element S multifunction display

It’s a good point, so the higher the better, but there aren’t really any alternatives on Maximus – unless we consider fitting an MFD to the washboard, which is what Richard says a lot of people are doing these days.

The problem with this, however, is that if you want to go below deck and the plotter is plugged in and running, you’ll have to lift your leg over the board.

Richard recommended the Element range of MFDs, which are button-only options. “For this boat the 7in would be perfect,” he suggested, although they do also come in 9in and 12in models.”

Tiller pilot

We’ve been so busy on Maximus that I hadn’t even discovered the Navico tiller pilot. This was despite the fact it was right under the leaky window, which I’d spent a good amount of time fretting about! It was Richard who found it hiding under the boat hook.

If we decided to upgrade the tiller pilot (which Richard estimated to be around 20-25 years old) we could opt for Raymarine’s ST1000 or 2000 series.

Designed for tiller-steered yachts, these removable cockpit autopilots have a built-in compass and there’s even an autotack feature which lets you handle the sheets whilst the tiller pilot tacks the boat.

If power consumption is a worry there’s AutoSeastate, which keeps the boat on course whilst conserving power. Maximus is on the heavier side, so would require the ST2000 tiller pilot, designed for boats up to 4,500kg displacement (fully laden).

The Sailor radio

As you may have read in PBO’s letters pages, the vintage Sailor radio remains popular today, even though it’s at least 40 years old. Richard was delighted when he saw it. “You’ve got an old Sailor radio! You’ve got to keep that, right? You’ve got to keep it for nostalgic reasons.”

Richard’s not the first person to suggest I keep it. In fact his colleague, Greg Wells, has passed it on to his brother Rob, a radio enthusiast, who is fixing the Sailor radio right now. You can follow his progress here and on PBO’s YouTube channel. It’s looking hopeful…

If Rob can fix the Sailor we’ll have the small issue of running two VHF radios side by side – completely unnecessary, I know, but I don’t want to part with the beautiful Sailor! Modern radios just don’t have that same appeal.

“If it works you’ll have to have two separate VHF aerials,” advised Richard. “You couldn’t rely on one, and the two will need to be at least 1.5m apart so there’s no interference.”

Richard suggested we have one aerial on the back of the boat and another one at the top of the rig (our electrician recommended the Vtronix Hawk antenna).

We would need a splitter, but he pointed out that the AIS 700 transceiver has a built-in splitter so the cable will come from the aerial into the AIS unit and split back out to the VHF.

“You actually have most of the channels you would today on the Sailor VHF,” he pointed out. “However, by putting a more modern radio on you’ll have private channels added, and the DSC (digital selective calling) feature.”

Ray73 VHF radio

DSC is a definite bonus, allowing the radio to transfer information not just by voice, but digitally, sending an instant position and distress alert to the Coastguard.

That would certainly give me peace of mind when sailing with our three young children. “Push the red button,” is a much easier instruction than trying to explain how to do a Mayday, even though a follow-up voice call is still required. Hopefully we’ll never have to put it to the test.

We’re likely to go for the new Ray73 VHF radio with AIS and a loudhailer. With the GPS integrated into the VHF we don’t need the standalone Garmin GPS which is currently onboard.

The built-in AIS receiver is another benefit. We’ll be sailing in the Solent shipping lanes and hopefully crossing the Channel one day so it would be good to use the AIS to keep a safe eye on ships, especially at night or in reduced visibility.

Richard also pointed out that with two sources of AIS, from the Ray73 and AIS 700, and GPS in both the Ray73 and Element MFD, there will be some issues needing data source selection.

We’ll be testing all these products on board Maximus so I’ll let you know how we get on. First things first though… it was time to meet the electrician and get his verdict on the wiring. At least now I had a better idea of what we wanted.

Thanks to our Project Boat Supporters

Dell Quay Marine, Osculati, Raymarine, Shakespeare Marine, TruDesign, Screwfix, Coleman Marine Insurance, MDL Marinas, Premier Marinas, seajet, Marine & Industrial, Clean to Gleam, West System, Farécla, Navigators MarineRYA, Aqua Marine, Ecobat, Victron Energy, Scanstrut, T Sails and XP Rigging.

The hard sell…

Do you know any young boaters or people who dream of owning a boat one day? A recommendation from you to start reading PBO could save them money in the long run and means our experts can continue helping all boat owners with their problems.

Subscribe, or make a gift for someone else, and you’ll always save at least 30% compared to newsstand prices.

See the latest PBO subscription deals on magazinesdirect.com