Problem Solving

This section is designed to help members to identify and solve common faults that may develop from time to time. If any member feels they can contribute further content for this section of our web site, or wishes to make any relevant comments, please email to

Boat Serial Number: Many owners ask how to find the serial number of their boat. The HIN No (Hull Identification Number) is normally found on an oval plaque with "Seamaster Ltd Dunmow" engraved upon it. Commonly screwed to the main bulkhead above the instrument panel. Not all boats were "Factory Built" with a HIN No. Many were owner or boat builder completed. If you cannot find the HIN number it is sometimes worth looking at the back of some of the wooden panels - many models were individually built and their parts each had the HIN number written on them.

Measuring Air Draft : A useful tip picked up from the message board:
The best way is to measure it yourself. Equipment changes since she was built may mean that she is sitting lower in the water, thus reducing air-draft and increasing draft. What I did with my 27 was to tape a spirit level to a piece of batten (say 2x1) and place one end on the top of the screen. When level, measure from the batten to the water's surface, then do the same with the screen down.


      • All systems are dead.
      • Some circuits are working but others are not.

        All systems are dead.
        The most likely sources of problem are:
        - A flat battery
        - A Faulty connection to the battery. If the battery is not flat a good starting point for tracing the fault is to check that the connections to the terminal are clean and making good contact. To help prevent problems here, smear the terminals and their connections with petroleum jelly to hinder corrosion.

      • Some circuits are working but others are not.

      One very common fault, easily remedied, is that one or more fuses are not making contact properly. So, turn off the power, locate the fuse box and remove each fuse in turn (remembering which place in the fuse box the fuse belongs in). Clean each end of the fuse gently to remove any or all corrosion and then return the fuse to its place. When all fuses have been cleaned, you should have your circuits back.

Repair or Replacement of Alternators.
The original alternators were known as "AC" type. They will have separate regulator, control relay and 3AW warning light relays either fitted in the electrical locker on early engines which were originally painted "Battleship Grey", or on the back of the cylinder heads on later "Blue Painted engines. These old fashioned type of alternators are better than the new type in my opinion, its sometimes difficult to get them serviced but well worth it if you can find a nice old fashioned firm that can do them.
My reason for favouring the AC type is that they re-charge the batteries much more quickly than the later ACR type found in modern cars these days.
ACR alternators are very good at delivering high outputs when you load them with heated rear windscreens, seats etc on cars but not so good at charging batteries when no load is being used.
Paul Killick

Leaking Windows. Click here to download an article on re-sealing windows on a Seamaster 30. [ Newsletter, volume 10 issue 5]


Engine Over-heating - The following give advice on some possible causes and cures:

Basic checks: First check that there is water in the engine and that water is being expelled from the exhaust showing that raw water is circulating properly.

  • If there is insufficient water in the engine, top it up.
    Check that there are no water leaks by inspecting hoses and water pump. Replace as necessary.
  • If there is no water coming out of the exhaust, check that the Sea Cock is open; if not, open it.
    Check that the weed filter is not blocked: close sea cock, remove weed filter, wash out and replace, re-open sea cock.
    Check the impellor is not damaged; if it is, replace it.

Click here to download an article on curing over-heating on a Seamaster 30. [ Newsletter, volume 10 issue 3]



I have a 27 with a 1500 BMC diesel engine. At up to 2000 revs no problem, exceed this and temperature goes through the roof. I should add its keel cooled. I`m planning on removing the thermostat to see if that helps. Can you help?


Its a little unusual to find a 27 with keel cooling, It may have been fitted due to being used on canals where weed can be a problem blocking the inlet.

With no problems at lower revs there is presumably water in the system, the weed filters are clear and the fan belt is still there, etc.

I think checking for a thermostat is a good idea to start with, adding a cleaning agent to the system while your about it would be a good move.
Back flushing the entire cooling system using a hose may reveal lots of sludge which can reduce the cooling capability of the keel cooling pipes,
oil coolers in the system can also become blocked over the years as can the heat exchanger..

You can check the opening temperature of the thermostat by placing it in a saucepan and heating the water until it opens, measure the temperature as it starts to open and again when its fully open.

I wouldn't remove the thermostat as a permanent fix, that engine is designed to run HOT not stone COLD. A new thermostat opening at around 75-80 degrees should suffice.

Let me know how you get on, I might have some other ideas once the basic checks/maintenance are carried out.

Leaking Water Pump - Do you have a problem with your Jabsco Water Pump leaking water, this could be a cheap repair, with a bit of luck, but can be expensive. You can get away with the leak for a short period, the trouble is that the seal also lets in air when at higher RPM. This can lead to overheating and eventually no cooling water at all

To do it yourself, follow the following steps:

Remove the water hoses.
Remove the four 1/2" bolts around the pump body.
Withdraw the pump from the engine.
Note;- Affixed to the pump is a drive shaft, affixed to that is a drive gear. The drive gear is machined to fit over the drive shaft and is held in place with a roll pin. The whole lot will come out with the pump, don't worry.
Remove the pump end plate.
Remove the impeller.
Note;- An easy way is to use two flat bladed screwdrivers, insert between the impeller vanes and prize out by levering against the pump wall. (The impeller is a spline fit onto the shaft).
Remove the cam. This is attached to the pump housing via a screw through the housing.
Remove the drive shaft with the drive gear still attached.
Note;- The drive shaft is held in place via a bearing which is push fitted into the housing. Secure the pump assy in a vice, tap the drive shaft using a copper tipped drift or hammer. The shaft & bearing will come out in one through the back of the pump housing. Be very careful not to damage the splines.
Remove the wear plate. This is located in the impeller housing against the rear face. It has a small "U" shaped cut out which locates the pin on the end of the cam.
Note;- This can sometimes be difficult to see in an old pump, remove by using a small screwdriver located in the "U" shaped cut out. If you cannot do this it should come out with the seal in step 9.
Two seals are pressed into the housing, one for water the other for oil, to remove these use a small drift and tap out backwards through the hole where the shaft fitted.
Note;- Remember which way round they were, one side is flat and the other concave with a circular spring. This side always goes towards the liquid it is sealing out.
By now you should be able to spot the cause of the leak. Possibilities are worn seals or worse still grooves worn into the drive shaft where the water seals runs.

If the drive shaft is grooved, you will have to replace the drive shaft. These are expensive at around £70. I have repaired them, but it doesn't last long!

TIP;- There could be a cause! High vacuum. Its worth checking the oil coolers, take the things right off and see what's inside. Two types were used, one made slightly different to the other. If you have the type with a large rubber reducer its easy to remove any debris from blocking the small tubes within. Any scale build up can be removed by immersing in vinegar for a couple of days.
Back flushing the system is a good idea, in case any debris has built up in the gearbox cooling jacket.
If you have to purchase a new drive shaft you will have to knock out the roll pin to separate the drive from the gear. The new one will not have a pre drilled hole, this you will have to do yourself. I would suggest a local engineering shop is used, drilling the shaft must be very accurate. A pillar drill will be required.
Don't skimp on replacement parts, replace everything you removed. This includes the bearing, wear plate and cover plate, even the cam and the screws. It will cost around £130 , ASAP normally stocks the lot.

Don't forget to order the gasket that fits between pump and engine, coat all new gaskets with a thin film of heavy grease.
Also grease the entire pump body inside as you build it back up, this prevents premature wear of the impeller. It runs dry for a while until the water reaches it.

If you need further advice contact Paul Killick: email or phone 07831 204549. He is happy to provide advice to members for no charge.

If you are not happy to do it yourself, contact him for a quote. He will have to charge, as it is his job, but offers Seamaster Club members a discount on all work done.

Care & Replacement of Fuel Tanks, (based on a Seamaster 30)    
The tanks fitted to 30`s are very prone to damp at the rear corners/bottoms caused by an accumulation of dust and dirt building up where you cant see it. Rain water and leaks run down the cockpit side panels and onto the backs of the fuel tanks, this soaks into the dust and debris and starts the rust. making them corrode outside inwards.
Another common leak is through the deck fillers, water runs down the filler pipes and puddles on top of the tanks.
The tanks are not difficult to remove, once emptied and the wooden retaining stringers removed, the filler pipes and fuel feed return pipes can be disconnected and moved clear. You have to turn the tank on its side and put ropes under each end. Two people can then lift the tank up though the floor bearers on its side. I have undone the threaded metal inlet pipe to make it easier on some boats, that's if it will unscrew fairly easily.
Keeping the inside of the tanks clean also illuminates corrosion from the inside out.

The fuel Tanks on 30`s were made by "SERK SERVICES", They recondition tanks made by them but of course its down to logistics. They are based on the A3 somewhere, Sutton comes to mind. One has to deliver the tanks of course. Have had good reports on tanks repaired by them, the last owner I know of was "KIWI LADY" Roger Burnay.    
Contact Paul Killick for more info.    
Condensation in Fuel Tanks
Click here to read a contentious article on "The myth of Condensation in Fuel Tanks".
On Calorifiers

When replacing the calorifier on a twin engined boat it is worth considering a "twin coil" calorifier, this will give the added advantage of being able to heat the tank from both engines, either engine, or electricity via a mains immersion. available. (Immersion heaters are available in 1kw-2kw or 3 kw ratings. The marina cable/fuse size will dictate what size immerssion heater you can have but the 1kw is normally sufficient.
If you ever decide to fit/replace the boats heating system, it is also possible to use one of the coils to heat the tank via the heater. Eberspacher Hydronic is a good make! I have fitted these to several boats and they are quite impressive.
One more tip, get the largest cylinder you can easily fit into the space. The reason is that to get hot water out you have to put cold in, that means that you only get half a tank of hot water in reality.
A well insulated tank should hold it's heat comfortably overnight. If yours does not, investigate the insulation.

Osmosis and Hull Blisters
Click here to read interesting articles on the reasons for Hull blisters and their treatment.
Flag Etiquette when dressed overall
Click here for Flag Etiquette when Dressing Overall (for a Commodore's Sail Past, etc)

To be continued



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