Technical Questions Answered…

Why is there a lot of noise and vibration coming though the boat, particularly from the stern end?
A common cause of noise and vibration through the boat from the stern is a worn cutlass bearing.   The cutlass bearing, which supports the shaft, can be found inside the p-bracket or stern tube, depending on design.  The shaft is prevented from damage as it spins inside the cutlass.  The most common cutlass bearing comprises a grooved rubber centre surrounded by a brass shell.  Also available are fibreglass and phenolic types.  The shaft should be a snug fit through the cutlass.  Over time as the bearing’s internal surface wears down against the shaft, additional space is created inside the bearing allowing for excess movement by the shaft. This movement causes noise and vibration through the vessel. Unfortunately, the only way to resolve this issue is to replace the bearing.

How do I replace my gland packing and how do I know what type to use?
Gland packing is used to make a water tight seal around the shaft at the inboard end.  There are two main types of gland packing available, PTFE (white) and Graphite (grey).  Basically, Graphite packing should not be used in saltwater; however the PTFE version can be used in all water types.  Occasionally, grease impregnated flax is also used.

To replace the gland packing, the first thing you need to do is take off the stuffing box and remove the existing packing, taking note of how many turns of packing there are around the shaft. You must now clean the stuffing box before re-packing it.  If you have a water-fed gland, this is simple and a quick wipe with a damp cloth will do the trick.  However, a grease-fed gland will require more thorough cleaning.  To re-pack the gland, wind the packing around the shaft, slightly overlapping and cut through using a sharp blade at a 45° angle which makes a better seal than a straight cut.  Repeat the same number of turns of packing to what you removed.  The seams of each piece needs to be staggered against the next, thus creating a water tight seal.   Reassemble and tighten the gland.

How often should I replace my anti-freeze?
Antifreeze is important – not only does it protect your engine from frost & ice damage, it is also a good summer coolant as it will protect all areas of the engine’s cooling system against rust and corrosion, so is best used all year round.

Antifreeze should be mixed with water, in a 50-50 ratio.  We would recommend a good quality anti-freeze is used; an Ethylene Glycol based product is best.

All antifreeze can degrade over a period of time, thus its effectiveness is reduced and the level of protection against frost damage is also decreased.  We suggest changing the antifreeze every two years, however it’s always best to check its concentration on an annual basis.

Should I change the engine oil before the winter or in the spring?
During the summer season whilst your engine is running potential harmful bi-products are produced from the combustion process which can build up in the engine oil.  Therefore we recommend changing your engine oil and filters before the winter lay-up reducing the risk of internal surface damage from prolonged exposure to these nasties.

Should I worry about the new type of diesel?
No….don’t worry, just be aware…
Recent legislation has led to a change of fuel used on the inland waterways.  The new fuel must contain no more than 10 milligrams of sulphur per kilogram of fuel and can contain up to 7% bio diesel.  Diesel bug is especially fond of bio fuels so this 7% addition can increase the likelihood of encountering issues in your fuel system. Protecting your fuel against diesel bug is therefore even more important. Water in the fuel is the number one cause of contamination where condensation collects at the bottom of the tank, filling your tank before leaving it over the winter is the best way to avoid this.  In addition to this draining off excess water from your tank and separator filter is a good way to ensure you have as little water in the tank as possible before leaving the boat over winter.

In older engines it is a good idea to keep an eye on fuel hoses and seals as these may be affected by the new additives.  Modern diesel engines, however, should not be affected.  It would be advisable to check with the manufacturer.

How do I maintain my batteries over the winter months?
It is advisable to take the time to properly maintain batteries prior to storing.  If you have wet acid or flooded type units they may require some attention.  This is a simple case of checking the distilled water level and topping up if necessary.  If your batteries are AGM or Sealed, i.e. don’t have removable caps then they will not require any maintenance.

When left for a prolonged period of time the cells can discharge to the point of no return, meaning you return to a costly replacement job in the spring.  To avoid this with small engine batteries that can be transported easily it is a good idea to take them home and store them in the garage where you can periodically top up their charge.  For bigger batteries or large banks of cells, isolate them from any potential load.  This is to reduce consumption from devices/appliances on board which can draw power even when not in use.  Over the course of the winter, in some cases this could be enough to flatten the batteries.  Charge the batteries occasionally to maintain the charge.

It is important to bear in mind when isolating or disconnecting batteries that this may affect the operation of the bilge pump.

The exterior of my engine is rusty.  What could be causing it and is it something which needs attention?
This may be an indication that there is a water leak from a pipe joint or from a gasket or casting.  This should be investigated and repaired as required. The corrosion will have to be cleaned off and the area primed and repainted.  It is easier to keep a check on a clean engine than a rusty one.

I read that most marine engine damage results from the failure to maintain the cooling system.  Can you give me some pointers on what to do?
Overheating is a common reason for engine breakdown and there can be a variety of causes.  Firstly you need to check if you have cooling water flowing through the system.  If this has stopped or the flow reduced you need to check the intake filter, impeller in the pump and also check that the first cooler before or after the pump is clear as weed can sometimes pass by the filter and restrict the flow.  Something that is often overlooked is the flow of the water after it leaves the heat exchanger/engine into the injection bend/mixer.  This is prone to corrosion that can restrict the water flow and cause the engine to overheat. If the water pump is getting on in years it may be that just changing the impeller will not be enough and the complete pump needs to be overhauled or replaced. It could be that you have a good flow of water but the heat is not being dissipated between the engine’s two cooling circuits due to scale building up around the heat exchanger or inside the engine’s internal capillaries causing a blockage. We recommend that the heat exchanger tube stack be cleaned every 200 hours.  As always good maintenance will help prevent overheating problems.

My boat is normally just used at weekends.  I have recently retired and am planning to cruise on her throughout the summer.   What steps should I take to prepare her for continuous use?
The first thing to consider is the existing systems/engine up to the heavier use, e.g. battery bank/charging system.  Whilst this may have been ok for a short trip, will it be suitable for continual use, including days where you might be moored up and not travelling?  It may be worth considering a larger battery bank and the means to charge the bigger bank as you can’t have one without the other.

It will also be very important that the engine and gearbox has a major service as this will probably be working harder in a month than it has done in the last few years put together.  This service should include oil and filter change, fuel system check and filter change; fan belts should be replaced as well as the water pump impeller.  It would also be prudent to replace all engine hoses and clips. Its all about limiting the potential problems before they arise.

It might be worth enlisting the help of an engineer for a few hours and discuss your intentions with them as they will be able to identify possible problem areas and suggest the best way to improve things.


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