Haines Hunter V19R project boat | Wiring and electronics
When we last visited our ripper Haines Hunter V19R project boat she had just gone into Henry Hill’s spray booth. When painting a boat
Next on the agenda were the outboard engine, electricals and marine electronics.
Here Michael Fitzallen from Nautek Marine talks us through the many important steps that go into a proper wiring job in a project boat. Did we mention he has an avionics engineering degree?
PROJECT BOAT ELECTRICAL FITOUT
The key to any boat restoration job, including an electrical installation, is to start from the ground up and work to a plan. An electrical plan looks a little like a tree starting at the base and branching off to all of the components with the foundations for future growth. It all stems from the amount of power you can generate and store.
Our Haines V19R project boat — since dubbed the Nautek N19R — produces plenty of power at the propeller, as well as 50amp from the alternator charging system. Many older engines produce less than 25amp and others have alternative sources of power including generators, shorepower, inverters and solar, but none of these are usual in trailerable boats. Some will have a detachable trickle solar unit to keep batteries charged in storage but that’s about all.
Your electronics plan on your restoration boat needs to consider all of the items you wish to run and start and for a worst-case scenario based on how long you will run lighting and accessories without starting the engine. While many items such as LED lighting are far more thrifty with their current draw, we continue to fit more power-hungry appliances such as massive multifunction units (GPS, radar, colour sounders), TVs, berley dispensers, bilge pumps, spotlights, etc.
In other words, you need to calculate how much you can produce and how much you need to produce, and from that can be calculated your storage requirements, remembering that engine starts, electric anchor winches and all other electrical components need peak power sources.
Power use estimates leads to correct battery selection. There are a multitude of different batteries but for our Haines V19R our friends at Exide batteries recommended a marine stowaway starting battery as well as an AGM battery fitted with a VSR (Voltage Sensitive Relay).
The marine stowaway starting battery features cells with thicker lead plates producing more cranking power but less amp hours over a drain. Outboard engines need immediate grunt for a short peak load, especially with EFI (Electronic Fuel Injection). We use the engine battery in conjunction with an AGM deep cycle battery. This fairly new breed of maintenance-free, high-current output, long-life battery will perform to a really low drain point and then charge back up again quickly. Michael tells us that customers often shy away from them as they are around 30 per cent more expensive, but it's false economy as they last much longer on average.
AGM batteries have a fibreglass weave between the plates that actually absorbs the acid but stops the sulphation from sitting on the plates. It also aids electrolytic flow. They are humorously called ‘sailor proof’ in the trade, as yachties are notorious for leaving their batteries turned on and destroying them in the process.
I was interested to find out that many larger outboard engines supply dual power cables to feed twin-battery systems. As most good batteries can only be charged at a maximum of around 40amp there is sufficient power to charge both. Many boaters still use single battery systems, particularly in small boats but as a battery can drop a plate any time it’s wise to consider alternatives such as emergency jump packs.
VOLTAGE SENSITIVE RELAYS
Voltage sensitive relays for marine use have developed in leaps and bounds in recent times. VSRs sense the load inline between two batteries and divert power to equalise the two. Most are now solid state silicone-based units without minute mechanical parts to fail. They are particularly important in multiple charging systems with generators, shorepower, solar and engine alternators, as they sense the load and divert it to needy areas.
Michael said: “Electronics are renowned to fail, so we give ’em the best chance we can."
“Older VSRs basically had a mechanical clicker that would just look for high voltage on one side and send the power to the other. Our new VSRs will always leave power in your engine start battery. They are smarter, stronger and much more reliable!”
There is a centrally located on/off power switch for each battery on the Haines V19R, as well as an emergency parallel switch which basically joins both batteries together to combine their power for an unexpected failure, or if you fall asleep and it all goes flat.
Marine batteries need to be secured to a solid base and preferably with stainless steel supports. The plastic mounts work okay but often get very brittle. Many boats now have dedicated battery compartments that are off the floor and out of harm’s way. We’ve all heard many a tale of the damage that a thrashing tuna or shark can cause kicking around a boat, so you don’t want your batteries and electrical wiring exposed to the unexpected.
The experienced crew at Nautek Marine simply don’t like battery terminals. Michael said: “They are 1950s technology and are just another connection to fail. It doesn’t matter how clean you keep your boat, you will still get salty moisture causing corrosion.”
Nautek uses the screw terminals on the top of a battery as a priority and keep the connections to a minimum at this critical point. It’s crucial to keep the connections tight as loose terminals won’t operate correctly and they can also damage equipment, cause sparking or — in extreme circumstances — an explosion and fire.
Keep them tight but take care not to over-tighten as you can easily snap them off, rendering the battery virtually useless. It is also vital to use one of the rubberised battery terminal sealants to minimise corrosion. If you have ever seen the sparks fly when you drop a gaff across the battery terminals you’ll know why battery protection is important – it is frightening and very dangerous.
PROJECT BOAT WIRING
Just as batteries ain’t batteries, it seems that wire ain’t always wire either, and tinned cable is the only really acceptable alternative for marine use. Tinned cable is not only almost corrosion proof but it can actually carry more charge due to its high silver content – hence less voltage drop.
Michael said: “We still see some low-end manufacturers and contractors using non-tinned cable but the result is generally failure. Also, look out for multiple-strand wire over solid core as it generally handles larger vibration without snapping.”
We run the large main house (positive) and negative wires to individual terminal blocks (large insulated stud) and take fused or circuit breaker systems off each.
Many people use stainless steel bolts for this purpose but it’s not a great idea as stainless steel doesn’t carry current well. The correct studs are tinned brass. We have even seen people bolting straight through aluminium hulls, charging the entire boat and causing a very dangerous situation plus electrolysis. Be careful that the first supply run wire is large enough for the entire boat current draw, plus 20 per cent.
Remember the tree. The stump must be the strongest and thickest to carry all of the individual branches. Excess draw can create heat and corrosion. Blackened wires may occur from heat and corrosion, meaning there is too much current draw off the circuit.
Michael said: “We often see wicking from poorly sealed wiring. Wicking occurs when a cable is in touch with saltwater. It will draw salt corrosion right up the wire. Heat shrink and sealant are very important.”
WHAT CABLE THICKNESS TO USE?
We asked Michael what cable thickness to use when doing wiring on a restoration boat and his immediate response was to do an avionics engineering degree in the RAN like him – in jest, of course.
There are Australian Standards for both 12V and 240V systems. The applicable one for the Haines V19R is specific to short runs like our six-metre boat. A rule of thumb is 1mm² for every 10amp minus 10 per cent for smaller current-drawing systems.
Going too thin can create major problems with heat. Too big is better but can cost a lot more and the physical rigidity in tight places isn’t practical.
Michael said: “Recently we have seen some problems with modern LED lights. They require very little power and hence are supplied with thin wiring, but the wiring doesn’t stand up to motion and vibration terribly well.
“For most of the accessories commonly used on trailerboats, we use 1.5 to 2.5mm² that will safely handle between 10 to 18amp. A marine radio may only use half an amp in standby but it will peak at 5 to 6amp while transmitting,” he adds.
There is peak loading on startup for most accessories but modern cables are built to withstand such impact. Your calculations should not be based on the combined minimal load. Work out your requirements, including allowance for future plans for the total feed, and add 20 per cent.
Nautek actually constructed the entire loom for all of the power in our Haines V19R on a planning board before installation (above). Michael explained that his aviation background required much higher standards than the marine industry and the quality was regularly audited, but they continue such practices in their boating facilities.
The main power feeds should always be run to an unswitched fuse block and individually dispersed from there. Some systems need individual switching and some don’t. For example, navigational lighting needs to be individual but depthsounders don’t. Do not double up on wiring into a fuse block. If required, run a bigger or multiple blocks.
Make each component an individual circuit and label them. Colour-coded wiring is certainly recommended and can make fault finding so much simpler but it’s not always practical, so labelling at each end is acceptable. Each circuit also needs a fuse or circuit breaker and it’s a real no-no taking multiple accessories from one fuse.
Remember, if you blow a fuse then nine times out of ten there’s a fault and not a dodgy fuse. Michael said: “Circuit breakers are quite reliable. They also stop dummies from putting overrated fuses in systems, when they continually blow for other causes and there is a reason why fuses blow! There are now dedicated marine circuit breakers but most are still open from the rear and need a good heat shrink and perhaps plastic boxing to avoid corrosion.”
We asked Michael about electrical interference and he explained that all outboards have terrific interference suppression nowadays. He explained that the most common cause of interference is a dirty alternator, power cables too close to the VHF transmission coaxial, or inverters and some generators.
“Most problems can be fixed with suitable conduit or sensible placement of wires,” explained Michael. “We believe in the use of conduit wherever possible. I can’t emphasise strongly enough the need for conduit, shrink wrap, suitable terminals, secure cabling and sealant on all marine electrical circuits.”
ELECTRIC WINCH CURRENT DRAW
Other than engine start, electric winches are the biggest current draw on any boat. Nautek always takes the winch feed from the engine battery and emphasise that the engine should be running and hence charging for operation. Many people use the winch to drag the boat up but in reality you should take the load off by aiding it with the engine. Sensible ergonomics are essential, so be sure in your dashboard plan that you can operate the throttle with one hand and the winch switches with another.
Winches definitely need their own circuit and power feed from large cables. Small wires over a long length will lead to a big voltage drop and create heat.
Winches have switches and solenoids, so care is required. Michael said: “Winches create a huge current draw and may shut down electronics if wired incorrectly. For instance, many GPS units will drop out at 11V, so wire accessories to the house battery circuit and the winch to the engine battery to avoid problems.”
A FINAL WORD
There is a lot more to marine electrical systems than meets the eye, and plenty to go wrong for the inexperienced. There is a reason why we have trained professionals for these purposes and hence we strongly recommend that you consult a qualified contractor before attempting any installation.
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See the full version of this story in Trade-A-Boat#455, July / August 2014. Why not subscribe today?