Tony Brooks

But I think it should have at least one anode bonded internally to all the metal parts that are underwater to stop those metal parts corroding. Even proper bronze has different metals in it, and although they claim aluminium bronze is galvanic resistant, I suspect the aluminium just reacts more slowly than the zinc in brass. However, I am unsure how one or two anodes will protect the metal underwater fittings more than a couple of meters away. I am a bit surprised the boat does not seem to have a shaft anode to protect the prop because there are no signs of bonding brushes on the shaft inside the boat.

If you buy one of the square solenoids (slightly more modern design) you can easily get them apart to look at the contacts. It is only 4 rivets to drill out, then they can be replaced with nits and screws. The type Bizzard linked to have the insulated terminal end swaged into place, so is more difficult to get apart and far more difficult to re-swage. The square type is the one shown in the manual I found and may well be the one Lister agents would supply. I don't think they are particularly less reliable than the round type. There is not much inside either type apart from a single coil, a contact bar, and two contact pads that are part of the terminal studs, so I too suspect the fault may be else where, like a terminal with a poor connection (crimp) to the cable, or, as said, a problem inside the starter. After all, those solenoids are designed to pass the full petrol engine starting current, but you are only passing the current the starter's internal solenoid coils require, which is likely to be far less. Sorry, I do not have any values. I wonder if internal modern solder joints are failing, but if so pushing the "button" should still operate the starter, so the fact it does not suggests dirty/burned contacts or an open circuit elsewhere. Some square ones have a little rubber (often red) push diaphragm to bring the contacts together, others do not.

Sounds like you bedded the impeller blades in, but why that was needed I have no idea, and by the way, it won't be 10K revs, the BMC 1.5 (automotive) should be set to top out at about 4400 rpm. You probably mean 1000 rpm. If it was not anew pump, I would have suggested that the end plate and wear plate, either side of the impeller, were badly worn.

Do you have any sort of silencer, or water separator in the exhaust line, if so it might be worth taking it out to see if anything odd has happened inside it? Boats of that age often had a rubber expansion box that looked like a pair of cones pushed together.

One other thing. If the hot, out connection on the Webasto runs downhill from the boiler, be prepared to loosen the joint to let air out of the system, if the Webasto pump does not cause it to self bleed. If it does not then the boiler will fire up, run for a sort while, and then shut down, with the Webasto connection being hot, but the rest of the hose/pipe still being cold.

You may find it cleaner to use something like a drill pump to drain the system down if the drain point is within the cabin. If it is extended into the engine area (assuming a rear engine setup) you can drain into the bilge rather than into shallow containers. Mix the antifreeze and water BEFORE refilling the system and on no account exceed a 30% mixture, 25% is probably better. If your system happens to have a pressurised expansion vessel, rather than a reservoir/expansion vessel, then you may need a pump to refill and pressurise it.

FWIW, not having specific experience. Looking on Google images, it looks as if that solenoid may be mounted on a bracket on the engine, if this is so the first thing I would do is move it to a mounting somewhere on the boat. It seems solenoids like this and relays mounted on the engine tend not to take kindly to the engine vibrations. The diagram in a manual I found looks very like an ordinary relay rather than a solenoid. If it is a small (rectangular box) relay, then I would change it for an inertia starter solenoid. You say it keeps failing, exactly in what way?

The one I saw was two half couplings welded together, but it could be machined from a large diameter metal "rod" or even hard wood. I think that I would have changed the studs on the back for set screws, but I bet they are an odd thread for nowadays like UNC. As long as they stayed oil free we fund them good flexibles and if not oil free, a readily obtainable spider - every town had a BMC garage at that time. refitting the spider and keeping the two faces aligned was the problem.

Yes, exactly that.