How do you know if your boat is operating right?
There are a set of simple test tricks to know if your boat is performing the way it is expected to.
Your boat has a basic set of parameters dictating performance expectations that the builder released when the boat was originally sold new, these numbers are an idea in most cases. These parameters would have or could have included information such as top speed, RPM at full throttle, weight of the vessel with full fuel and water, fuel burn expectations, etc. However after some engine operation hours your horsepower numbers will begin to drop off, the weight numbers will vary from boat to boat simply because some boaters will keep a lot of gear and items on their boat , other owners will have next to nothing. If you start to add accessories like a tender, radar arch, swim platform extension, a replacement swim platform or adding a big generator. Then you have definitely changed the weight of the vessel and could possibly have changed the center of gravity and created a load shift backward/forward or side to side of the vessels center line.
Changing the load from the center line or changing the center of gravity will totally change the expected performance of the hull and the way the boat rides on the water. Large loads can create changes that the hull cannot recover from, an example of this is when the load shift from center line will no longer allow the hull to get on a natural plain position. The bow will simply not drop. The only way to fix this type of problem is to start changing props, modifying or installing a hook in the hull, this is a type of permanent trim tab. You can also add more weight to the fore ward hull. All of these modifications can bring the bow down, however all these modifications will mean that your fuel bill will climb substantially. A really good accessory designer will keep this information in mind and recommend installation location instructions specific to your make and model of boat. Adding accessories like extended swim platforms can really affect the performance of the hull when backing up or travelling in following sea conditions.
This means that the new swim platform can act like a trim tab and keep the hull from rolling from bow to stern. This can create lift at the transom and make the boat very "transom loose". Which creates a situation were you loose the ability to steer the boat. In the worst case of operation in a following sea the back of the boat can be lifted up and come around to try and pass you. This is when the weight of the boat is being placed on the mounting point of your new swim platform and the water can rip it off.
Other situation that can be created is a "list" when the load weight is not even from side to side, this situation is enhanced at high speed. The boat starts to lean over and becomes unstable. You can try to correct this with trim tabs but if this is a must all the time you must address the list. If you continue to run a boat with a list you will eventually stress the trim tab and the trim tab ram or trim tab will eventually give up. Balance from side to side is far more easily addressed than any other balance problems . The load on the boat can be moved around, the best place to start is with the batteries etc. If you find the boat is listing and slowly getting worse you may have a leak, and a floatation locker maybe slowly filling up. This type of leak can go on for a long time and never show any water in the bilge. To figure this problem out you will probably need to bring in a surveyor to tell you were this maybe taking place.
When it comes to the engine there are some simple tell tail signs that you need to have some mechanical work done. What you need to do is start by reading the water, this means on a nice calm morning start the motor or motor(s) one at a time. Immediately go to the back of the boat and look at the exhaust water and the water around the back of the boat. If you see a slick of gas on the water then the motor is not cleanly burning all the gas it is consuming. This is the sign of requiring at least a tune up. If you have twins with thru hull exhaust check the water flow against each other, if one motor flows more than the other then you probably need to change a sea water pump impeller in the motor with less flow. This same trick can be used for inboard out board units. With the engines off trim the drives up and down and look for any oil slicks if there is a leak in a seal the small leak will create a slick on the surface of the water. For trim tabs use the same test. Any kind of slick is a sign that something is wrong! The water around the back of a boat that is running right will be clean.
The exhaust smoke color can also tell you a lot about what is going on with the motors. White smoke is usually just steam. A little bit of white smoke is not a horrible thing on start up or after a long run coming off plain but it should clear up quickly. However white smoke that has a sweet smell means that you are burning antifreeze from your closed cooling system. Black smoke is carbon, which may just mean the boat needs a good high rpm run to clean up and heat up the motor, or it could be a sign of bad spark plugs. Blue smoke is oil, this is a sign that you have a motor that is getting tired, if it is just blue at the start then you have a valve train or ring problem and again will need to get this fixed. This means some type of engine tear down. Any off the above problems will affect the performance of the motor(s) and this will affect the boats performance.
Take the boat for a ride and bring another driver with you. This is so you can read the water again. The information you can get from this is interesting. Look out the back off the boat while you power up through the rpm range, watch the wash coming off the back of the boat it should be even on both sides, when you do this "do not" use the trim tabs at all. Look at the prop wash and you should see a nice even flow of water, if you have twins the wash should be the same on both sides. When you get to 2500 plus rpm with twins if you match the rpm's on port and starboard motors the boat should start to sing. The sound will be even and matching (the sound should be like one motor). When this happens, run the boat like this for 15 min or so the sound should remain even and solid you will hear it if a motor starts to lag or miss immediately. With some experience doing this you will easily be able to pick out the motor that is acting up. Now take a peak up the sides of the hull and see were the water is breaking out from under the hull and how far the spray travels this will let you know if you are running with any list on plain.
When you are out for your ride you can test the rpm ranges of your motor(s), you should have push all the way from idle speed right through the range. Check the following. When you push the throttle and the rpm increases quickly but the boat is slow to react or it sounds like the motor is not loading up (Slipping), or at the top end of the rpm range the maximum speed of the boat is obtained way before full throttle is obtained, and the last of the throttle range just increases the rpm only, These are signs that you have to re prop. The best way to do this is to call the engine manufacturers and they will ask you a series of questions to determine the best prop for the performance you are trying to achieve, improving the prop can make a huge difference in performance and fuel burn.
These are simple tips but they really do work try them out on your boat or your friends boat. Reading this is may explain why quite often a mechanic will start the boat and step off the back and stare at the water he/she is reading the signs the boat are giving. A lot of times problems will show up here first before a break down. A boat is much like a car, it will tell you what is wrong, most cases long before a larger problem arises, the trick is to know what your boat is telling you.
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