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Design Services:
We can offer a wide range of design services not just in the purely marine field.
Please ask about system design, PC installations, UNIX installations and general programming skills for PCs and microcontrollers (PIC and PC-104 type controllers). Quick Basic and Visual Basic a specialty.
We have facilities to cope with the volume production assembly, test and repair of electrical units.

Boat sitting service. I'll look after your boat while you're out of town. Check lines, run engine (if you wish), take care of emergencies, make sure your dive service is doing work OK, etc. Please call for competitive rates! Local area only.

Specializing in:




Energy Systems:

Batteries, solar, wind, alternators, regulators, chargers, inverters & monitoring systems.

Expert GPS and DGPS recommendations

Teak finishing/varnishing

We recommend the use of Sikkens CetolTM for the protection of external teak. It is easy to apply, requires fewer initial coats and is easily maintained by applying one additional coat per year. Whereas the finish is not high gloss like conventional varnishes, the advantages of using this highly UV resistant coat far outweigh any cosmetic preferences. During prepping we precisely use a small orbital sander, not a belt sander and apply blue long-life tape before work starts in order to protect the gelcoat from scratches. Meticulous finishing is ensured. A unique final UV protection coating is applied for long life.

HF radios, antennas & tuners

VHF radios

Marine Air Conditioners

Dunedin Marine Systems is owned & operated by Paul Evans and has a wide range of experience in electronics. He holds a degree in Physical Electronics (Physics & Electronics) from the University of Warwick, England. He has been involved in the manufacturing, design and testing of semiconductors as well as running complex design workstation systems.

Paul has been a hands-on radio amateur since 1972 & has a particular interest in technical issues. He is joint holder of a US patent and currently is involved in two pending patent applications. A GPS industry expert since 1989, he recently presented a paper at the Technical Meeting of the Institute of Navigation held in Santa Monica, CA on GPS tracking systems.

Hints and tricks for looking after your boat

The lightning datasheet! (essential reading)
The corrosion / electrolysis datasheet (essential reading)
Florida Waypoint List

Oil for your diesel engine?

Don’t ever put S grade oil in your diesel! Oil that starts with S grade is intended for Spark engines, not compression engines. This is the stuff you should put in your car engine, not your boat engine! What are the compression grades?

CC good
CD better
CE better
CF4 better
CX best

In practice, you’ll find it difficult to find anything better than CF4 at “regular” stores. S grade oil breaks down very quickly under the 2.5 times compression ratios that are in diesel engines compared to gasoline engines (diesel=25:1, US gasoline engines=8:1, EU petrol engines=10:1). There’s a good reason why diesels need different lubricants (smell it and you’ll immediately know the difference).

Changing Halyards? To prevent losing a halyard while you’re trying to change an old one for new – do the following.

(a)    Wrap tape around each halyard (old and new) about 3” from the end. Pull back the outer braid to that point.

(b)   Take the core and heat the end so that it is sealed and creates a slight mushroom end.

(c)    Take adhesive lined heatshrink tubing and push one core in one end and the other core in the other, so that they overlap with the mushroomed ends clear of the tubing.

(d)   Shrink the tubing until it’s tight and the adhesive oozes out. Let the adhesive set for a few minutes. You now have a strong overlap with ends that cannot pull out!

(e)    Pull the braid back up to the overlap (trim if necessary) and wrap with a small amount of adhesive tape (not too much).

(f)     Hoist the new halyard using the old, pulling the free end over the mast. You shouldn’t even feel the joint go over the sheeve.

(g)    Take the free end and melt the core and braid together, then use a small band of heatshrink tubing to act as whipping. It’s much faster and easier than whipping twine.

Adding solar vents (electric) to your boat? Walk along the dock in any marina and you see it – solar vents put into hatches, forward hatches some of them! Ugh. Why take a perfectly good hatch and cut a hole in it that will let water through when seas come over the bow? Most of these seem to be fitted under the mistaken belief that they will help to cool the boat in the Summer. Come on. Think about it. Your big boat is closed up, sitting in the Sun in 93 degree water. There isn’t a hope that the tiny little fan will do anything to move any air out of the boat and cool it. No, the only reason to have a solar vent on a boat is to keep air circulating to reduce the amount of mould (such as mildew) that can grow. Put on the fan blade that sucks air out of the boat and you’ll see that the deck around it is covered in mildew after a while. These are spores that are now outside the boat, instead of inside it.

So, if you’re going to fit vents fit them far back on the boat away from spray. You can remove the awful looking dorades on most boats and fit the solar vents in their place. Given the correct fittings and neoprene O-rings you won’t get any water leakage into the boat.

Signalling Device on your dinghy? Our friends at the USCG actually warned some friends about not having a signalling device on their dinghy when just circling their boat. The way they made sure that this was not repeated was to tie one of the plastic orange whistles to a grab handle on the dinghy and leave it there.

Does your holding tank stink? (Even when at the dock and when you don't use it!?) This can be anti-social and imply in some less-educated boaters minds that your head is in use and you're pumping all manner of evil stuff overboard! Nothing can be further from the truth, because when pumped overboard in the kind of quantities that your typical holding tank contains, there is no smell!

First, click on sanitation and find the topic Odour Control at this excellent link from a major tank maker, and then come back here and read on.................

Well, having read that, you can see that a tank frequently smells because a head is not used or the system is badly designed in some minor or major way. The bad air is trapped in the holding tank and when the boat rocks a little (stepping on and off or the wind blowing [or actually sailing :-)] ) the sediment in the tank is disturbed. This acts a little like a pump and expels a very small amount of trapped air from the vent.... and el stinko! One cure for this is to keep the tank full so it cannot slosh around (although this is not recommended). Therefore, the smell can actually be worse when the tank has recently been emptied.

None of the normal products available at the major boating stores will digest the bad stuff and pump up the good stuff. Maybe Biologic RVM (shown in the above link) is worth a try. One of these days I'll try it and see if it is any better than Odorlos. More details of Biologic RVM are contained here, but there are, unfortunately, no details of retailers or distributors. If it's not readily available, it's not for me.

You should give Odorlos a try - it's at some of the major marine stores & they claim miracles for it. I've tried this and it works very well. It stopped all signs of tank smell immediately. You might have to add more if the tank contains waste for any period of time, but I don't think so.

Another untested treatment is BacTANKT3. You can find more details here. It seems to be on mail order only. They claim that one treatment per tank full is enough.

Old signalling flares? Do you keep your old signalling flares? It sounds like a good idea doesn't it? In a recent test we found that virtually none of old out of date flares which were out of date by only a few months would go off! They were kept in their container in a dry part of the boat too. I'd recommend that you immediately place all flares new or old in zip-lock bags to keep out the damp. Notice that new flares are in a bubble pack with a plastic front BUT HAVE A CARDBOARD BACK WHICH LETS IN DAMP. Take them out of the packaging and plastic bag them right away! Furthermore, never count on those old flares you saved thinking that they'll give you X more shots if you need them they may not go off. Try to use them first. It's really wise, when you think about it, to bag the flares because if you ever have to abandon ship to the dinghy or liferaft you'll have the flares in a dry storage bag so you can count on them in the wetter environs of the dinghy. More - the height achieved by the 12 bore flares was alarmingly low. Never hold a hand-held flare over head (like they say) because bits of hot contents dribble out all the time that it's running.

Got mildew in your gelcoat? You probably have, even if you can't see it. Very close inspection will show mildew spores in the top of the gelcoat, or if your boat gets it big time it'll be very obvious. To clean the gelcoat before washing and waxing, use a terrific product called Tile Plus Mildew cleaner. This I could only find in the local Publix. Other cleaners may not be so good. This stuff really is wonderful and is the proverbial spray on - wash off product.

Got a PSS shaft seal? Dripless shaft seals are great! You should never have to adjust them and you should just give them an inspection every season to check the clips and the boot. However, when the boat has been out of the water a small air pocket can be trapped in the shaft log. This will make the seal run dry and cause clicking. To fix this, drop the boat in the water and then go down and squeeze the bellows down the shaft to push out the air.......

Need a great glue? I found a really amazing glue called PowerPoxy Stix-On Contact. It's like a cross between SuperGlue and contact glue - but better! It also stays a little flexible so it doesn't break like SuperGlue does. This stuff is available in our local Home Depots. Try it! It's the ONLY glue that really will fix shoes (gives you an idea how good it is).

Low efficiency and cut outs with your marine air conditioner? Of course, the sea strainer needs to be checked about once per week, along with the through-hull, lines, etc. I started to get cutting out (overheating) of the compressor because the heat exchanger was running hot. There was enough water going through. So what was the problem? Answer - the inside of the exchange pipe was coated with gunk (algae, etc.) but not barnacles. This was reducing the efficiency of conducting the heat from the coolant lines to the sea water. Fix? Pull the input hose off the through-hull and dunk it into a gallon of Muriatic acid (Hydrochloric acid) used for swimming pools. Be very careful! This is fuming acid and it can overcome you quickly. Keep several gallons of water to hand in case of a spill. Run just the pump for about 3 seconds. Let the acid sit in the system for 5 minutes. Run the pump again for 3 seconds and sit again for 5 minutes. Add water to the acid to dilute. Keep sending slugs of more and more dilute acid through the system until you have plain water in the system. Pull the line out of the bottle and wash with clear water. Re-attach to through-hull. Enjoy cool air again. The difference in my system was amazing! The give away is that you get a dribble of green water stains down the hull at the outlet. This tells you that algae is growing in the system (it isn't coming directly from the water itself). Do this at least once a season to keep efficiency up (more on a fresh water lake, I would guess).

Don't EVER, EVER, EVER use a pressure washer on your topsides, deck or lines it will RUIN everything it touches and cost you $$$. Gelcoat will be permanently damaged by using a pressure washer. The only time a pressure washer should be used on a boat is very shortly after the boat is hauled out for a bottom job and should ONLY be directed below the waterline at the paint or running gear.

Got nasty brown stains on your hull after sailing the ICW? It only takes a few days on the ICW before you get brown stains (from Ferric Oxide - rust!) on the gelcoat, especially up near the bow. Getting this off used to require scrubbing with Barkeeper's Friend or similar abrasive paste. Try using a product called Rust Aid. This is a light acid which won't hurt your gelcoat or paint. You don't even have to scrub - just let it run down the hull and off comes the stain!! Hose off with fresh water and all is like new....

Want to make stuff last longer in the sun? Try using a product called 303. It's not cheap at $8 a small spray bottle. However, try it on fabrics, stitching and teak finishes. It has amazing UV blocking powers.

Need to clean Hyperlon fabric on your inflatable? There are numerous products for cleaning inflatables. One that worked well for me was fairly expensive ($6 for a quart spray bottle). Try using Windex, it's just the same ammonia stuff, but costs only $1 in a Dollar Store for the same bottle size! It works a treat.

Need to mount instruments on a binnacle grab rail (like Edson)? Try buying the nylon clamps that are used typically to mount teak tables to the 1" rail of the binnacle. Mount the instrument mounting bracket to the nylon bracket and you have a quickly adjustable and removable mounting!

Want to make oil changes easy? Get an in-expensive electric fuel pump, fit a switch so it can be turned on. Attach a line from the sump plug to the pump and from the pump to the rest of the world. Put a bolt into the open end of the line and clamp it on so it won't pop out under engine pressure! Changing oil is as easy as warming the engine, removing the bolt, putting the line into a gallon jug and switching the pump on.

Need small amounts of 110VAC power? Get one of the new generation of notebook computer inverters. These come in 140W and 300W ratings and are very small. I got mine (140W) for a mere $34! You can use them to charge cordless power tools or run 110VAC tools directly.

Need carpeting in your boat? Try shopping for shower mats! These are made in soft, plush materials and have super non-slip backings. They can be washed in a machine and are very long lived. They can be obtained in several different sizes. On my boat I used K-Mart shower mats in blue in 40" x 24" sizes (they fitted the main walk way perfectly).

Trying to lubricate boat systems? There's a new product call SailKote which leaves a totally dry lubricant on the surface sprayed. It was used on the America's Cup boats. I used it on my main sail traveller and a sticky head board on my main sail. It works a treat. It can be bought at West Marine, but the normal shelf price is not cheap! I just used this stuff on a Nicro Solar Fan which was a little slow. WD-40 has never really cured it. It whizzes around like crazy (and starts with very low light level) with SailKote on it!

Want to keep paperwork dry on a trip? Buy the one gallon size of the Hefty One Zip bags. These cost about $1.50 for fifteen bags and they'll take a single sheet of standard (U.S.) paper and keep it completely dry. Also there's very easy access using a zip on the bag. Use these to carry documentation with you when using your powered dinghy.

Building a new sanitation system (head and holding tank)? Don't use the white plastic sanitation hose! For some reason 1.5" hose and fittings are not made the same! The plastic hose sold at West Marine has to be heated and fought with to try to make it fit, with limited success. The same looking hose sold for use with Spas is a loose fit! Furthermore, despite what the marine industry will tell you, any loop in the plastic which holds even a small amount of sewerage will smell after a couple of months. ALWAYS use the black reinforced hose which is black with a green tracer (and made by Shields). Catalina use it on their production boats and there is no smell. I've visited boats with the plastic hose and instantly know the difference !!!!!!!!! Please be warned - the difference in price is worth it.

Racing? Try to find a weather site near you which records wind speed and direction on a graph. Try looking at this one for Clearwater. This will show you the wind patterns you may observe unless there is a front or similar event coming through.

The Blue Water Provisioning Datasheet


Never, never use Energizer batteries in your GPS receiver. They last the least amount of time of all the Alkaline batteries (a fact also highlighted by Practical Sailor magazine).

Use New England Rope docklines with the pre-spliced eyes. They are exceptionally well wearing and can carry massive loads. They'll last you 2-3 years at least.

Don't use the floating storage holster sold by West Marine for the Garmin GPS38. The top section covers the built in patch antenna at the top of the unit. After many attempts to turn on during a recent ocean voyage, I found that I had to slide out the receiver often to get a good fix. This was worstened when the holster was wet! It works fine with the GPS45 and other Garmin units which have an antenna outside the main housing.

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