Aqualarm Water Flow & Exhaust Alarm
This entire section is devoted to a $175 option on Alto, because it addresses an issue that anyone with a Ranger Tug, or any other boat, with any diesel engine should know. First, know these engines are all sea water cooled, sea water is sucked in through an inlet on the bottom of the boat which is pumped into a water jacket that surrounds the engine. The sea water, in turn, cools the Yanmar coolant fluid which is an antifreeze with no salt in it to corrode the interior of the engine. The seawater gets quite hot, and after circulating through the water jacket it is returned to the ocean through a big heavy duty hose (HD), like 6” in diameter. BTW, the water jacket has two sacrificial anodes made of zinc, which help reduce corrosion from the seawater; the antifreeze coolant does not need this sort of help as it has no salt.
In all raw seawater cooled diesels the engine exhaust gets mixed in with the seawater that is used to cool the engine, just before the water is discharged overboard. You’ll see bubbles and burbling gas in the water coming out from boats that have their engines turned on. This system quiets and cools the exhaust, but the seawater gets even hotter from the engine exhaust gases. Furthermore, once mixed, the seawater/exhaust gas goes through an even bigger HD rubber hose through a muffler, to further quiet the noise. The R-25’s all have a standard Velux muffler which is made of plastic and works quite well, normally.
However, engines fluctuate in how hot they get, and the new computer controlled commonrail diesels all run at very high temperature, close to boiling; furthermore, they have superchargers to force air into them to run even hotter. When the engine temperature gets too high, an warning alarm sounds off. This is most commonly due to seaweed growing on or around the seawater strainer inlet, on the bottom of the boat compromising the intake of raw water to cool the engine’s coolant, to cool the engine.
Sooner or later you’ll have to go over the side and brush off the seaweed, as you can’t run any engine too hot. If you are lucky, this happens while you are at the dock and you can hire a diver, or pull the boat out to clean the bottom. I bought a special diver’s mask with my eyeglass prescription built-in, as in warmer water I just anchor is 3 feet of water (remember Alto’s draft is < 2’) and scrub at it for a few minutes. But, you’ll get lazy and you can’t see the growth accumulating on your boat’s bottom which will have separate raw seawater inlets for the main engine and marine toilet, for the generator and for the AC system–three opportunities for clogs! This is so common, that my marina offers a monthly raw water inlet check and service program which most boats engage in, for extra cost.
Yanmar diesel engines all run at 190° at initial throttle opening (when the boat gets warmed up) and at 205° at wide open throttle (WOT). If the Yanmar ECU (electronic control module, like the one in your car) detects coolant temperatures at 226° or higher, an audible alarm sounds and the Garmin chart display blinks a visual alarm. The good news it that you usually have time to get somewhere and turn off the engine to let it cool, since the max. operating temperature is quite high–248° at which point the engine shuts itself down to avoid damage. The bad news is that your Velux muffler is made of plastic and melts at around 220°. I suspect you see where I’m going here…
By the time your engine alarm goes off, it is too late to save the muffler. It’s not earth shattering, but it costs between $200-$300 to replace it and it leaks raw seawater into the bilge until you do. It is a hassle, as remember, the hoses going to and from the muffler are huge, heavy duty with steel wiring in them for stiffness and strength. Getting them on and off the muffler can be tough! It’s better to just avoid the problem in the first place.
The less you use the boat, the more stuff grows under it. Since the new bottom paints are ablative, they shed-off taking with it growth, but this only works when the boat is underway. Since Alto did not get a lot of use, I’ve replaced a couple mufflers. Sooner or later you will, too, if you are not using the boat frequently. You’ll note that most used Ranger Tugs tend to have low hours, at least compared to the thousands of hours diesel engines are designed to go. Admit it! We tend to be casual users tootling along at low cruise speeds (10 mph) with dirty bottoms, having cocktails in the marina rather than crossing rough seas…
OK, so what’s the solution? Well you add an engine over-heat alarm that sounds off before 200° so you can take action before your muffler melts. Duh! It so happens this is a very common issue and boaters (more so occasional boaters then full-time loopers) add these alarms. They come in two types: 1. one has a sensor that straps around the big heavy rubber exhaust gases hose from the engine (left below), and 2.) one that measures the flow of water through the hose that goes from the raw seawater strainer to the engine’s impeller pump. This gets inserted into the hose and has a little rotor that spins when the water is moving through the hose (right below). It’s a no brainer, the best are made by Aqualarm and they look like this:
This entire section is devoted to a $175 option on Alto, because it addresses an issue that anyone with a Ranger Tug, or any other boat, with any diesel engine should know. First, know these engines are all sea water cooled, sea water is sucked in through an inlet on the bottom of the boat which is pumped into a water jacket that surrounds the engine. The sea water, in turn, cools the Yanmar coolant fluid which is an antifreeze with no salt in it to corrode the interior of the engine. The seawater gets quite hot, and after circulating through the water jacket it is returned to the ocean through a big heavy duty hose (HD), like 6” in diameter. BTW, the water jacket has two sacrificial anodes made of zinc, which help reduce corrosion from the seawater; the antifreeze coolant does not need this sort of help as it has no salt.
In all raw seawater cooled diesels the engine exhaust gets mixed in with the seawater that is used to cool the engine, just before the water is discharged overboard. You’ll see bubbles and burbling gas in the water coming out from boats that have their engines turned on. This system quiets and cools the exhaust, but the seawater gets even hotter from the engine exhaust gases. Furthermore, once mixed, the seawater/exhaust gas goes through an even bigger HD rubber hose through a muffler, to further quiet the noise. The R-25’s all have a standard Velux muffler which is made of plastic and works quite well, normally.
However, engines fluctuate in how hot they get, and the new computer controlled commonrail diesels all run at very high temperature, close to boiling; furthermore, they have superchargers to force air into them to run even hotter. When the engine temperature gets too high, an warning alarm sounds off. This is most commonly due to seaweed growing on or around the seawater strainer inlet, on the bottom of the boat compromising the intake of raw water to cool the engine’s coolant, to cool the engine.
Sooner or later you’ll have to go over the side and brush off the seaweed, as you can’t run any engine too hot. If you are lucky, this happens while you are at the dock and you can hire a diver, or pull the boat out to clean the bottom. I bought a special diver’s mask with my eyeglass prescription built-in, as in warmer water I just anchor is 3 feet of water (remember Alto’s draft is < 2’) and scrub at it for a few minutes. But, you’ll get lazy and you can’t see the growth accumulating on your boat’s bottom which will have separate raw seawater inlets for the main engine and marine toilet, for the generator and for the AC system–three opportunities for clogs! This is so common, that my marina offers a monthly raw water inlet check and service program which most boats engage in, for extra cost.
Yanmar diesel engines all run at 190° at initial throttle opening (when the boat gets warmed up) and at 205° at wide open throttle (WOT). If the Yanmar ECU (electronic control module, like the one in your car) detects coolant temperatures at 226° or higher, an audible alarm sounds and the Garmin chart display blinks a visual alarm. The good news it that you usually have time to get somewhere and turn off the engine to let it cool, since the max. operating temperature is quite high–248° at which point the engine shuts itself down to avoid damage. The bad news is that your Velux muffler is made of plastic and melts at around 220°. I suspect you see where I’m going here…
By the time your engine alarm goes off, it is too late to save the muffler. It’s not earth shattering, but it costs between $200-$300 to replace it and it leaks raw seawater into the bilge until you do. It is a hassle, as remember, the hoses going to and from the muffler are huge, heavy duty with steel wiring in them for stiffness and strength. Getting them on and off the muffler can be tough! It’s better to just avoid the problem in the first place.
The less you use the boat, the more stuff grows under it. Since the new bottom paints are ablative, they shed-off taking with it growth, but this only works when the boat is underway. Since Alto did not get a lot of use, I’ve replaced a couple mufflers. Sooner or later you will, too, if you are not using the boat frequently. You’ll note that most used Ranger Tugs tend to have low hours, at least compared to the thousands of hours diesel engines are designed to go. Admit it! We tend to be casual users tootling along at low cruise speeds (10 mph) with dirty bottoms, having cocktails in the marina rather than crossing rough seas…
OK, so what’s the solution? Well you add an engine over-heat alarm that sounds off before 200° so you can take action before your muffler melts. Duh! It so happens this is a very common issue and boaters (more so occasional boaters then full-time loopers) add these alarms. They come in two types: 1. one has a sensor that straps around the big heavy rubber exhaust gases hose from the engine (left below), and 2.) one that measures the flow of water through the hose that goes from the raw seawater strainer to the engine’s impeller pump. This gets inserted into the hose and has a little rotor that spins when the water is moving through the hose (right below). It’s a no brainer, the best are made by Aqualarm and they look like this:
Using the Aqualarm
When you start turn the key half-way, it activated the glow plugs you need to wait until the red light goes off, indicating they have warmed up the system enough to start the engine. During that 5–10 seconds the engine is not running, and thus the impeller pump is not running either, so no seawater is being sucked into the cooling system. Since there is no seawater coming through, the AquaAlarm senses no water and sounds off. It’s is loud and that is why there’s moot switch (see the red bottom in the above picture.
So mute the noise. If the alarm sounds while underway, that means there is no water circulating and while you can run for a while before the engine alarms say it is over heating, remember by that time your plastic muffler might melt. Try to “pull over” drop the anchor and turn off the engine as soon as possible. Then check the sieve (raw sea water strainer) plastic see-through cover for gook. You can TURN OFF THE RAW WATER INLET and then remove the plastic cover, and pick out any gook blocking the intake. If you don’t turn off the raw water inlet valve before you dismantle the strainer, you could sink the boat! If that doesn’t help, go overboard and peek at the exterior strainer, a slotted cover which is probably occluded by seaweed. Scrape that off, and you’re good to go. This is by far the most common reason for failure of seawater to get sucked into the engine to cool it down.
The last reason is your impeller is damaged in the raw sea water pump mounted on the engine. If the pump won’t suck, that no water comes through the system. This happens when the rubber fins on the impeller break off (usually after an engine overheating episode) although they do wear out. This is the reason you replace the impeller in all boat engines (outboard as well as inboard) yearly, or every other year if you don’t use the boat often. It’s a hassle, but any diesel mechanic or handy person familiar with removing fan belts to work on an engine, can do it in under two hours. Lots of videos on YouTube about this, here’s a tool that makes it easier.
<– Previous Page ––– Next Page –>
