In late 1992 my friend Les Caterson sold his Sydney dive charter boat Cat Dive. This was a 7.5 metre long Marlin Broadbill which he used to operate out of Port Hacking on Sydney's southern edge. In early 1993, after much searching, he purchased a 5.6 metre Marlin Broadbill for use as a private boat. In 1999 I purchased a half share in the boat and in 2011 I purchased it outright. We dive virtually every weekend, sometimes both days. We also dive on many Wednesdays. Les still dives with us most weeks.

The following article details the boat and gives some ideas about the set up of a similar boat for diving. In April/May 2004 we repainted the boat but some photos on this page are before it was painted. The boat is now blue.

THE BOAT ITSELF

The boat, called Le Scat, is a 5.6 metre long Marlin Broadbill. The Broadbill is an aluminium catamaran built in Sydney. They come in a variety of sizes from 5 metres right up to over 11 metres and in a few different versions. They are very popular with Government Departments such as Water Police, Waterways and Fisheries for use as patrol boats. They are also very popular as dive charter boats (in Sydney there used to be at least three, Sea Tamer II and Aquatic Explorers out of Port Hacking and one out of Broken Bay). Some of the keenest divers in Sydney also use Marlin Broadbills (Max Gleeson for example).

My boat was quite old, made in 1980. It is measured at 5.6 metres but this is equivalent in length to the new 6.2 metre boats. The new boats are measured from the bowsprit to the end of the walk-through transom whereas ours is measured from the bow to the back of the hull. For all purposes, they are exactly the same length. However, the older boats have a larger useable space for diving or fishing as the newer boats have a larger enclosed cabin area which cuts down considerably on the main deck area. Our boat can easily fit six divers whereas the newwer ones can only carry four. In addition, we can walk around the cabin to the anchor bay whereas the newer boats require you to go through the cabin and open a hatch. The older ones also appear to have much higher sides.

This shows the dash area, seats and bin Tanks go on right and left sides	Here I am towing Le Scat and we are at Yowie Bay boat ramp setting up for a dive

The boat has two seats for the driver and a passenger. These were originally set back a bit from the dash but were moved forward shortly after purchase to give more space and to enable the driver to be closer to the wheel. There was originally a game chair located on a large aluminium bin in the main deck but this was removed and sold. The large bin was located a bit back from where it is now but it was moved forward as when entering the boat from the water it was a bit too close and made it cramped. The bin now holds all fins, masks, wet suit tops, gloves and lights etc. It also doubles as a seat when travelling out to a site. When gearing up, it is a perfect place to set tanks before donning them. After a dive, it becomes a table for our after dive feasts. Four things in one!

Tanks are kept on the sides of the boat, strapped to the hull using weight belts. When repainting the boat recently, we put two strips of timber along the fuel tanks to protect the paint from being scratched. There is space for three tanks on each side (they will hold twins or a tank and pony for our deeper dives) and one tank can be strapped on one side of the transom at the rear. This holds our oxygen cylinder when we are deep diving. See later for safety features. Weight belts are stored in a crate behind the bin.

As mentioned above, you can walk around the cabin to get to the bow. We have a "roll-over bar" which not only holds a light illuminating the deck at night, it holds the aerial and dive flag anchor point. This bar is a hand hold while travelling along and it also makes it easier to move to the front in rougher seas. The anchor is kept in a small chain locker but the larger reef anchor will not fit and if we use it, we have to swap anchors once we reach a wreck (see later). It is stored beside the driver's seat, together with the O2 on shallower dives.

The boat has twin motors which means it has a walk-through transom, perfect for divers. There is a ladder attached here and this is designed so that you can exit the water with your fins on. See the attached photograph for more details. You enter the water by a backward roll or a giant stride through the transom.

The hull has had some minor repairs over the years. Things like small pin-holes in welds mainly. However, over Easter 2006 while coming back to Murrays boat ramp at Jervis Bay, we took on an enormous amount of water. We did not sink but it was a very uneasy trip back at 16 kilometres per hour. It turns out that the weld on the inner rear upper hull split for about 750 mm, letting in huge quantities of water. Luckily the hulls have floatation foam and the boat would not have sunk. The weld has since been repaired and all other welds examined and repaired where needed.

ENGINES

Until February 2005 we had two Mercury 75 hp engines that were probably 1980 models. They generally had proved quite reliable. Since 1993 they had been rebuilt once each and had done about 3,000 hours as at early 2005). These motors were capable of carrying six or seven divers and their gear at about 39 kilometres an hour with a little in reserve. The motors are running at 4,700 rpm at this speed and this seemed to be the most economical and efficient speed. The 75 hp has been sufficient but I would not like any less power with this load. The props were 18 inch.

On 9 February 2005 while going out for a dive, the port engine made an awful noise and I shut it down. It turned out that it had totally imploded and after some thought, Les and I decided to bite the bullet and get new motors. We purchased two new Mercury 75 hp two stroke motors with 18 inch props. We thought about getting 90 hp motors but the cost premium ($1,300 each) was too much in my view. We did not really look at four stroke engines but the significant weight and cost penalties were not enough to convince us that these were good value.

The two engines cost $7,787 each. We looked at Johnson 90 hp ($8,900 each with alloy props) and Yamaha 90 hp ($9,629 each). Together with fitting, a discount and trade-in of the old engines, the total cost to us was about $15,000. The engines come standard with stainless steel props.

Le Scat	Another shot of the boat from the rear quarter

The Mercury 75 hp engines have three cylinders and displace 1,386 cc. They weight 138 kg each and have triple carborettors and they are oil injected. Maximum revs is 4,750 to 5,250 rpm.

The new engines were first run on 14 March 2005 and on Sunday 20 March 2005 they had their first real run with divers. We had four divers and gear plus a non-diver on board. We were using the new props on the engines. These are still 18 inch like the old ones but appear to be a bit different in overall shape. With this load, the old engines would have done about 40 to 41 kph at 4,700 rpm. On this day, we used 4,400 rpm and we were doing about 42 kph. That is, using 300 less revs we were going faster than the old motors. When run at 4,700 rpm, we did about 46 to 47 kph. What a difference! At 5,000 rpm the boat did over 50 kph. No only are the new engines more powerful, they are so much quieter than the old ones. When you put the engines into neutral, you think that the engine has stopped, it is that quiet compared to the old ones.

Over Easter 2005 I took the boat down to Jervis Bay and we did a total of seven runs over the holiday period. Loads varied from three divers and one non-diver to six divers. However, due to the very poor nature of the Murrays Beach boat ramp (where we launch the boat - it is very, very shallow), we put the old props back on so that the new ones would not be damaged. The performance was very similar to the old engines, that is, about 39 kph at 4,700 revs with six divers.

On the weekend of 2 and 3 April 2005 I took the boat on two dives out of Port Hacking. The engines had their new props back on. The first was to the wreck of the SS Undola. On this dive we had five divers, all with pony tanks as well as the oxygen cylinder. The next day we went out with six divers. For both dives, the boat ran at about 39 kph at 4,500 rpm. At 4,700 rpm, it did about 41 to 42 kph.

The boat has two fuel tanks giving a total of in excess of 250 litres of fuel (not sure of exact amount as we have never emptied it - I did put in 200 litres one day - they hold perhaps 300 litres). We normally keep the fuel between 1/2 and 3/4 at the start of a dive. There is no point in carrying around extra weight unless you need to. This is more than sufficient for even the longest run in Sydney with a large reserve. The old engines gave pretty good fuel economy, with the only exception being in rough seas when a lot of throttle changes may be required. This increased consumption dramatically. Oil consumption was also very good except for rough seas when it goes up dramatically.

Over then next 11 years, we did about 660 hours on the new motors. The average fuel use was about 29 litres per hour, that is, about 14.5 litres per hour per engine. That is generally with six divers and gear on board.

HANDLING

In simple terms, a dream. The boat planes when full at under 4,000 rpm and appears to be best at 4,500 rpm with the new engines. At this engine speed it is doing about 40 kph. Running across flat water and tilting the engines up slightly (just before they cavitate) lifts the nose and cuts spray. So far the new engines appear to be little different to the old ones in terms of handling. However, when running into the swell and wind, the spray can come over the front and wet you (we normally have the canopy open). Once on the open ocean, it takes slight chop with no reduction in speed. Even in a fair bit of chop we can proceed at normal speed. This may entail a bit of leaping almost clear of the water but the cushioning effect of the twin hulls keeps it comfortable. In very big seas we can keep going where single hull boats have to turn around. There have been many times when we have been able to dive a site that single hulls could not reach.

Like all cats, it can be a bit difficult to handle when the sea is from the behind quarters. In such cases, the boat wants to breach (it won't, but it moves around a bit). I have discovered that using slightly more throttle on the motor on the same side as the direction the swell is coming from almost stops this tendency.

When anchored, the twin hulls make it quite stable for gearing up etc.

ANCHORS

For reef diving we use a large 15 lb sand plough with about 10 metres of heavy chain. There is 100 metres of 10 mm rope attached. We do not use a reef anchor for reefs as we do not want the boat coming free when we are diving. At the start of a dive, the first divers secure it and the last divers to leave the bottom place it at the end of their dive in a position where it can be easily retrieved. For wreck dives we use a large reef anchor (as the sand plough would grab in the sand that surrounds most Sydney wrecks). This has lead in its body to make it sink quicker.

When the anchor is on a deep wreck, we use a buoy to lift it to the surface. This is done by attaching the buoy to the anchor rope once we are ready to haul the anchor in and then running the boat forward. The buoy runs down the anchor line and lifts the anchor to the surface. Contact me for a more detailed explanation. We also have a winch to lift the anchor from normal dives.

When the anchor is in water any deeper than about 15 metres, we attach a cross-over line to it. This is a lead weight which is looped over the anchor and dropped. The other end of the line (about 30 metres), is attached to the bottom of the deco weight line. This deco line goes from the back right corner of the boat to about 12 metres. The cross-over line serves a few purposes. First, it enables divers to go straight down the deco line rather than swim on the surface to the anchor (especially good in heavy seas or currents). Once at the bottom of the deco line you simply follow the cross-over to the anchor. Secondly, the weight on the anchor end lays the anchor down more horizontally, thus increasing the effectiveness of the anchor and lessening the chances of it coming loose. Thirdly, by following it back to the boat, you slow yourself down on ascent from the 30 metre to 12 metre mark. Finally, in dirty water, it enables you to easily swim back to the deco line.

There is a spare anchor, chain and rope carried at all times.

SAFETY FEATURES - Including safe diving practices

The boat is equipped with 27 Mhz radio, EPIRB, depth sounder, GPS, First Aid kit and lifejackets. We carry mobile phones, a lot of drinking water as well as sun cream. There is extra oil for the outboards, jumper leads in case one battery is dead, spare anchor, chain and rope. I am a licensed Commercial Coxswain with in excess of 20 years experience. Kelly has been a licensed boat driver for 20 years and also works at NSW Maritime. I hold a Senior First Aid certificate as do many others who use the boat.

Specific items carried relating to diving are oxygen cylinder with long hose to enable oxygen to be breathed on decompression stops after deep dives, mermaid line for use in currents, a reel of line to extend the mermaid, dive flag, small oxygen cylinder for normal dives (in case of emergency), dive flag and extra weights for underweighted divers. The deco line (see previous items) is also a great safety feature, enabling divers to deco while holding a line that is not as subject to movement as an anchor, the cross-over line enabling divers to avoid swimming on the surface before a dive. We also have diving spare parts (like fin and mask straps, spare regs and even an extra dive computer).

Le Scat off North Bowen Island at Jervis Bay	The deco line and weight and the crossover line

The people who use the boat are generally very experienced. I have done more than 3,100 dives (see My Dive Info Page for more information). The average number of dives completed by the people who regularly dive with us would be almost 1,000 dives. Since most people on the boat have already dived the locations we visit, dive briefings are not normally given. However, we give full and complete briefings to people who have never visited the site we are diving and in most cases, one of the people who are very familiar with the site will accompany them.

When diving, we always have people either in the boat or under it. The boat is never left unattended in case the anchor breaks or comes free. On deep dives, we dive in pairs. The last two can enter the water before the others have surfaced or indeed, returned to the boat. However, they must not leave the anchor unless they have seen the first two divers ascending and received an okay signal from them. On shallower dives, we set a time limit for the first two divers. They do not have to ascend, but have to be back at the anchor or under the boat within sight of the deco line by this time. If the last two divers do not see the first two and get an okay, then they cannot move away from the boat. This has worked satisfactorily since we implemented it in late 1993. We often do drift dives in which half the divers enter the water and the remaining follow in the boat. This process is repeated once the first divers have finished their dive.

When deep diving (over 35 metres), we prefer divers to have a back up air supply. In most cases this is a pony bottle. Some use twin tanks. We will not take anyone, no matter their professed level of training or experience, on a deep dive unless they have convinced us that they are competent. This convincing is only achieved by diving in normal circumstances with us and then we make a decision as to whether we will take them deep. Quite a few times we have declined to take an allegedly trained and experienced diver on a deep dive till we see them in action.

COMFORT FEATURES

The boat has a dry area at the bow. We carry a dive bin here in which we put all clothes. After a dive we normally change out of our wetsuits into dry clothes, especially in Winter. We also store our food and drinks here. We have a system for a warm shower after a dive (to wash salt off and to warm up). There is a canopy over the cabin area and we can erect a cover over the rest of the boat on hot or wet days.

We even have two Apollo underwater scooters that divers on the boat can use!

TRAILER

Le Scat is carried on a dual axle trailer. It has mechanical brakes. It used to have rollers but Les and I converted it to skids. This was because the rollers kept breaking as the boat did not sit exactly evenly on all the rollers, giving undue pressure on some rollers. The skids, after a bit of modifications, are working okay. However, it was a bit harder to launch on a shallow ramp (the boat does not slide as well on the skids) and you needed to bump it off. It was also a little harder to drive the boat back onto the trailer as more power was needed to overcome the friction. In late 2002 we started to grease the skids and the boat now slides off the trailer and is much better to drive back on the trailer. All in all, it is much better.

In late 2002 we put new axles, hubs and brakes on the trailer as the bearings had started to fail at very short intervals. This dramatically improved the reliability of the bearings, giving at least 12 months without failure. In early 2009 we totally rebuilt the trailer, with new axles, hubs and most major steel parts.

TOWING

I originally thought that the all up weight of the boat and trailer, with half a tank of fuel, was about 1,800 kilograms. However, after I ended up scrapping it, I think that it weighted at least 1,950 kg based on the weights of the various parts as I disposed of them. I use a Toyota LandCruiser Prado (V6 3.4 litre petrol engine) to tow. My Prado is capable of towing okay but on some hilly locations where I have to stop for a red light, it is hard to get restarted. From the main place where we launch the boat (Yowie Bay boat ramp), while I can use high range, it is better to use low range till I get up out of the valley.

On trips to Jervis Bay I have found no problems in towing it, even back up Mount Ousley where I use second and third gear. Fuel consumption is about 17.5 lites per 100 kilometres when towing (compared to 14.5 around town and 12.5 in country). Maximum speed that I feel safe towing such a big boat is 80 kilometres per hour.

In April and May 2004, we decided to paint the boat. "About time!!" a lot of people would say! As mentioned above, the paintwork left a lot to desire before this. A lot of work was involved in stripping the old paint off, this took quite a long time. At the same time, we took the opportunity to remove the floor, clean it and get rid of the old carpet. We also changed a few minor things and had new bollards welded on and the six fishing rod holders removed from the gunwhale (and the holes welded over). The last of the eight coats were completed in mid-May 2004 and the boat is a nice blue colour on the outside and cream inside with black on the hull bottoms, stern and between the two hulls. See the photos above. Hard work, but worth it. In early 2005 Les painted the dash and the forward fibreglass deck cream to match the inside of the rear part of the boat.

SUMMARY

All in all, I know that our old boat was the best set up private dive boat in NSW. It was even better set up than most charter boats I have been on.

Diving is meant to be fun, it was on Le Scat (and still is on our new boat).

LE SCAT'S END

Le Scat being lifted off the trailer	Ready to be chopped up for scrap - a very sad day