Tony Brooks

Not if you use the correct sized tapping drill, which is unlikely to be a standard whole and half mm one. Then, as long as you have enough clearance behind the steel use a taper tap.

Just make sure that it matches the sender you get, there are two standards and if you mismatch them the gauge will not read the correct temperature.

Are you asking about a temperature gauge SENDER? If so you can get (at a price) combined senders and overheat switch. Beta use them. If not I am sure ASAP Supples or similar can supply a T piece to put both a switch and sender into the one hole. Sorry, i don't know the thread size. Edited to add: here you go for a combined sender and switch https://vdo-webshop.nl/en/34-temperature-sensors

Second one, but this type may be easier because the action holds the rivet in place rather than you trying to squeeze the handles and keep it pushed in.

Thanks, Jon, in that case the calorifier is acting as the bypass circuit, much as I suspected it might, but it seems as if the OP's boat is different, or he has not understood it. Edited to add. Although the calorifier take off is on the thermostat housing it is on the engine side of the actual thermostat valve, so is effectively an identical circuit to the vast majority of other engines.

If your original diagram is correct, then you say the flow goes from the engine to the calorifier and then through the skin tank. If so, the full coolant flow has to pass through a 15mm tube in the calorifier. That is far from ideal in my view. Fine for canals, but likely to cause overheating when pushing current on rivers. About a half inch bore (15mm o.d.) tube seems a bit large when compared with other bypass port, but it really is suck it and see. At least a 15mm bypass is more restrictive than what looks like 22mm on your original photo. Your description does not clarify the arrangement to me, in fact it seems to confuse things more. Hopefully someone with more knowledge and one of these engines will be along to help you.

Unless set up and used properly many battery monitors just lie, that is without the possibility of incorrect wiring, however, usually they say the batteries are better charged than they really are. In any case, battery monitors usually only monitor the domestic battery bank. You made a proposal to just link the two banks, most people who know feel this is a bad idea and I explained why. You don't need to understand why, just don't do it. You can link them as a TEMPORARY measure only when charging is taking place - probably solar. I also gave you one way of doing it that avoided the potential difficulties, but again, any competent person you get to do such a job should know what to do. My main reason for posting was to let you know that despite possibly significant sulphation the start battery may well still work well enough once recharged, so don't go buying new until you try it.

FWIW I used a plastic picnic knife to cut off he surpasses butyl and no sigs of a scratch. A wooden knife would do as well.

Starter batteries have a very easy life, only having to provide a few Ah per start with a decent engine. This seems counterintuitive to many. So you may be happily surprised if you can get that battery recharged. However, the fact it went so flat suggests there is a chance it has started to internally short, but definitely recharge it and see how it goes. The problem with a simple link to the starter battery is if it starts to short, it will flatten both banks. You can use a VSR to "unjoin" the banks when no charge is present.

Without seeing the whole circuit, I can't be sure. First off, have you got instructions from Redsaws for the correct way to pipe the housing. I say this because the calorifier/cab heater circuit is sometimes used as the bypass. What type of thermostat is fitted. It could be a bypass stat (two types) which will shut off the bypass when the engine is hot. A photo would identify it. The bypass port/hose on engines so equipped often has an i.d. of perhaps 5/16 to 3/8 of an inch, so naturally controls the maximum flow through the bypass.

Just make sure it is closed cell foam tape.

Certainly, the emulsifying type additive will create cloudy fuel when water is emulsified in the fuel.

If the butyl tape was what I used then yes, it would "mould" around the porthole, but despite what Truckcab says mine did squish out and continued to squish out for several months.

I say OK is you are sealing with an adequate thickness of closed cell foam, but if using a mastic type sealer, I would fear the rivets may squash too much out. You could try rivet nuts or simply tap the cabin side and use set screws. With the window out you may find countersunk wood screws through the cabin side securing the lining framing.