Michael McFadyen's Scuba Diving - Mak Cat
For information about the purchase of our new dive boat, replacing Le Scat, click here. For details about Le Scat, click here.
The boat, called Mak Cat, is a 6.2 metre Sailfish. The Sailfish is an aluminium catamaran built in Northern NSW. Over the years since they started building them in 1993, a variety of sizes from 5.0 metres right up to over 20 metres have been made. It is a bit hard comparing various models over the years as the model designations have changed many times and the designation does not necessarily indicate the size of the boat.
They are very popular with Government Departments such as Water Police, Waterways and Fisheries for use as patrol boats. There also used to be one running as a dive charter boat in Sydney.
Our boat was made in 1995. It measures 5.5 metres from the bow to the stern, but if you include the bowsprit and the transom, it is actually 6.2 metres. This is what it is registered as and what the model was called. It is very wide, 2.35 metres inside and 2.44 metres overall. The deck space behind the seats is 2.35 metres wide x 1.76 metres long compared to 2.0 x 1.92 metres in Le Scat.
While our old Broadbill let us walk around the cabin to the anchor bay, this one requires you to go through the cabin and open a hatch. I would much prefer going around, but it is not too hard (but it means we get water in the cabin after the dive!).
The boat has two seats for the driver and a passenger. We removed the large bin (700 mm x 700 mm) from Le Scat and installed this in Mak Cat as far forward as we could. The bin 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!
|Mak Cat anchored at Barrens Hut on a dive|
Photo by Michael Roelens
|Mak Cat coming back into Port Hacking after a dive|
Photo by Aidan Slevin
Tanks are kept on the sides of the boat, strapped to inside of gunnel the using weight belts. I also put a large swimming pool noodle along the lip of the pocket inside the hulls to protect the paint from being scratched. However I later removed it as it pushed the bottom of our dive tanks out too far and they were no standing vertically. I replaced it with a simple rubber protection strip.
There is space for three tanks on each side (they will hold twins or a tank and pony for our deeper dives). The rear starboard one holds our oxygen cylinder when we are deep diving. See later for safety features. Weight belts are stored in two small plastic bins in front of the seats under the false floors I had installed.
We have a "roll-over bar" which not only holds our GPS aerial, it holds the VHF aerial and dive flag (in a fishing rod holder). This bar is a hand hold while travelling along. The normal anchor is kept in the chain locker and the reef anchor (for wreck diving) is stored in the forward cabin in a dive bin.
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 photographs for more details. You enter the water by a backward roll or a giant stride through the transom.
Mak Cat has two 2003 Mercury 75hp 4 stroke (model 75ELPT S4) engines. These had about 330 hours on them when we got the boat in early 2016. The props are stainless steel 16 inch pitch. I thought we may need to change to the 18 inch ones from Le Scat but we seem to have the right amount of torque and top end speed so I will not change.
The Mercury 75 hp 4 stroke engines have four cylinders and displace 1,523 cc. They weigh about 177 kg each (compared to 138 kg for 2 stroke and not 162 kg as claimed in some specifications) and have 4 carburetors. Maximum revs is 5,750 rpm with the props we have installed (16 inch).
|Kelly at the rear of the boat on Mak Cat's first dive||The port engine of Mak Cat|
On 24 Aril 2016 Kelly and I took Mak Cat out for her first run. We did not have anyone on board nor any load. Launching was a bit of a problem as the ramp we used was at a very low tide and it does not have a great gradient, especially at low. I had to back up and stop hard many times before it would come off the trailer. I realised I would need to grease the rollers and runners so it goes on and off a lot easier (this was also a problem on the old boat till we did this). On our first two dives the greasing worked perfectly, it goes on and off much better.
Once in the water we took her for a run up the Georges River. The boat planed at about 3,000 rpm and at 4,000 rpm we were doing 20 knots. This is the same speed as Le Scat did at 4,750 rpm (but with a near full load). We will also need to remove the live bait setup as once we took off, water poured out of the hose, as it is powered by the forward movement of the boat.
When we finally took her out diving (with four on board), we did 22 knots at 4,200 rpm and 28 knots at 5,000 rpm. Later we did 33 knots at 5,750 rpm, almost 61 km/h, again with four and dive gear on board. Sure flies! Even with five on board, it did 20 knots at 4,200 rpm.
It seems to me that it is best (economy and handling) at 4,200 rpm. Our old boat required the engines to be tilted up till they cavitated and then dropped back till it stopped. This gave the best ride. On this boat doing that puts the bow too high in the air. Accordingly, we need to tilt the motors up only a little bit to get the best out of both the engines and the boat. Removing the trim tabs from the engines also made it far less "twitchy" when adjusting the trim.
One thing that concerned me about these engines is that when you put them into neutral after running at speed, there is a whining noise from both engines. It is not there when you first start the engines, and it is not always there.
I did some internet searching and found that this appears to be a common situation with Mercury four strokes of this age and similar size. It appears to be caused by the driveshaft vibrating and only occurs after running at speed. I read that it can be stopped by putting the engines back in gear and then back into neutral. I can confirm that this works. Another problem is that when the engines are first started, sometimes an alarm went off. Again, this appears to be common. It is the oil pressure alarm but stopping and starting the engine makes it go away (seems to only occur on cold mornings when oil is probably thick).
Now that we have done a lot of hours it is possible to work out the fuel economy pretty accurately. The tanks are said to be 100 litres each (according to specifications I have found on the net) but I am not aware of exactly where they are located (they are under the floor - forward or aft of the filler?) nor the actual dimensions, so this does not make it easy for me to measure the fuel level unless the boat is on level ground. I use some thin long dowels down the fuel filler and have marked them off in 5% increments. It seems that the 100 litre size is probably correct as adding 20 litres to a tank takes it up about 20%.
As of 23 February 2017 and about 55 hours, the engines use a constant 15.0 litres per hour (7.5 l/hr each). This is at about 4,200 to 4,400 rpm. This less than half the fuel used by the engines on Le Scat.
The boat has two fuel tanks (which feed an engine each) giving a total of 200 litres of fuel. I will normally keep the fuel between 1/3 and 1/2 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. I figure that a full tank will get us about 14 hours run time, that is, about 285 nm or 527 kilometres!
Our old boat (Le Scat) used to easily carry six divers and gear (five on deep dives). However, as Mak Cat has less deck space and is much heavier in the stern due to the heavier four stroke motors, we know that we cannot carry six divers. For the first six runs we carried four divers and this was very comfortable.
After I moved the batteries (and some other weight) forward, I decided to take out five divers to see how that went. On 22 June we dived with five on board. This was comfortable and we were no more stern heavy than with four. We will take five divers from now on if there are that many who want to go. I only take four on deep dives as we have more tanks and gear. There is space for six tanks.
Like most cats, in simple terms, generally extremely good. The boat planes when full at under 3,500 rpm and appears to be best at 4,200 rpm. At this engine speed it is doing about 40 kph (just over 20 knots). Running across flat water and tilting the engines up slightly (only a touch) lifts the nose and cuts spray. However, when running with a strong wind on the beam, the spray can come over the sides and wet us.
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.
|Mak Cat at the boat ramp||Putting Mak Cat back on the trailer|
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. I think that this boat is a bit better compared to Le Scat as it is not as twitchy.
One problem we identified early one was that when you suddenly pulled power off, water came into the boat over the transom. However, once I moved the weight forward, this seems to have basically gone away, although I do not pull off the power very quickly. We can still get some water in when at rest if we have too many at the stern or if we have seas coming from astern. I also put a blocker under the transom door to limit water ingress.
When anchored, the twin hulls make it quite stable for gearing up etc.
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.
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.
|The dash showing the new carpet||The new false floor after I carpeted|
it showing the new weight bin underneath
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.
SAFETY FEATURES - Including safe diving practices
The boat is equipped with VHF radio, EPIRB, chartplotter, depth sounder, GPS, First Aid kit and lifejackets. We carry mobile phones, a lot of drinking water as well as sun cream. There is a set of jumper leads in case one battery is dead. I became a licensed Commercial Coxswain in 1991. Kelly has been a licensed boat driver for over 20 years and also worked at NSW Maritime a couple of times and holds SES boat certificates. We are both volunteer members of NSW Marine Rescue. I hold a Senior First Aid certificate as do many others who use the boat. We always log on with Marine Rescue when we go out, using a phone app that gives them our location every 30 minutes.
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, 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).
|The rear deck ready to dive||Another shot cockpit showing all the work we did|
The people who use the boat are generally very experienced. I have done almost 4,000 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 over 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 insist on divers having 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.
The boat has a dry area at the bow. We carry a number of plastic bins 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 for morning tea here.
|Mak Cat at the Yowie Bay boat ramp wharf||Having morning tea at Jibbon after a dive|
Michael Roelens at left and Les Caterson right
We have a system for a warm shower after a dive (to wash salt off and to warm up). This was a pressure pump that sucked water out of a container and through a pet shower head but it is not working great. I have reverted to our old system of a watering can head on a water container. Nice! There is also 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!
Mak Cat is carried on a dual axle aluminium trailer. It has mechanical brakes. It has skids rather than rollers. We have an electric winch to pull the boat back on the trailer if needed. Normally we drive it on but the boat ramp at the yacht club does not permit this, so the winch will be very handy once everything is set up (still need to recable some parts).
The all up weight of the boat and trailer, with half a tank of fuel, is about 1,650 kilograms (we think - based on claimed towing weight with 2 strokes of 1,450 kg). It is certainly much less than our old Marlin Broadbill as it is easier to tow up out of our street. 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 onto the flat section of road. 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.
The cost of the boat and modifications etc was as follows:
|Item||Cost||We sold some items from old boat and this one||Item||Sale Price|
|Welding, pumps||$1,100||Trolling arms||$325|
|Various items||Bow roller||$15|
|Deck Paint||$44||Hull aluminium||$560|
|Pipe for cover||$||Old trailer||$800|
|Spare wheel carrier||$40||Ebay fee||-$199|
|Bollards (x2)||$34||Foam/cabin dumping||-$58|
|Waterproof containers (x2)||$40|
|Small Bins (x2) and large bucket||$20|
|Goof Off (glue remover)||$51|
|Trailer rego transfer||$47|
|Boat rego transfer||$30|
|Boat rego (personalised)||$176|
|New carpet and glue||$103|
All in all, I know that Le Scat was the best set up private dive boat in NSW. Mak Cat is not as good a boat, but it is still one of the best set up private dive boats in NSW. They are even better set up than most charter boats I have been on. The big advantages of using our own boat is that we have everything on board we need, we know where it is (as do most of the friends who dive with us) and we dive where we want to. We also dive places that charter boats rarely or never visit.
Hopefully we will get as great service out of Mak Cat as we did Le Scat, although I doubt I will still be diving in 23 years!
Diving is meant to be fun, it is on our boat.