Some of you have asked some good questions. Let me work through them with an explanation. The Marina I am in is at the head
of a very long sound. Two small rivers empty into the head
of the sound. This keeps a very narrow and shallow channel open. I get ruffly two to three hrs(depends on tide type) each side of high tide to come and go through the channel, after which it becomes to shallow for my draft
. The first leg of the channel is a straight line from the marina entrance and would be about 1000m in length. The channel is just wide enough for me to pass an on coming boat, but no more. At the end of that straight is a hard to starboard bend around a headland. The headland is all rock and the other side of the channel is shingle bank below the water. The water is murky and so you can not see the bottom. There is quite a current
running to add to all that. It is very much a, "stay within the markers and hope you don't drive by brail" type navigational excersise. A bit nerv racking for those that get to do it for the first time, but with experiance it is not so bad.
So hence there was no way of dropping anchor
or raising sail, as wind
and tide would have taken me up on the banks or into the rocks.
Now to the temp questions.
Being a short stretch of waterway and the fact that the Marina speed limit is 3kt and the channel speed limit is 5, the engine was only idling, so the massive amount of engine (6.354 perkins) takes some time to warm up. By the time the Exhaust failed, the engine temp was only 40degC. By the time I slowly got back to the birth, the engine was still not quite full temp. She has a big engine water system which kept everything all under control. I must say, at first I was worried that maybe the guage was lying to me. This can happen in some situations with some engines. The senders are placed above the Thermostat and if they engine runs out of water, then the sender is out of the cooling fluid and it tells you a false low reading. My system is built that the header tank and exchanger are all above that level, so it would have to be a major coolant failure to have the sender dry.
Kanai, you asked a very good question about introducing cold to hot engine. If it was a Raw water cooled engien, then yes that could be bad. But in this case, the cold is only going through the heat exchanger
. So there is no thermal shock.
Rodney, yes I have an Alarm system that goes if the engine also goes over temp. This is a seperate sender to the temp gauge sender which is a good thing. It means you have a "second opinion". So without the alarm going, I had a confirmation that the engine temp gauge was indeed telling me the truth.
Hope that answers the questions.
I must take a photo
of the channel and post it.
In fact, has anyone got the ability to do a "google earth" of my area. I can't, my computer isn't upto spec. The channel is about 7Nm of narrow shallow water way through mud flats etc.