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Morgan Paul · 17-12-2007, 15:36

Quote:

Nothing like that re assuring gush of water splurting out of the exhaust when you fire the motor.

You do not need any expensive sensors or other bulls**t. Just your eyes.

Paul

SkiprJohn · 17-12-2007, 15:52

Hard to keep your eyes on the exhaust all the time. Looking once and then forgetting about it doesn't really help if a plastic bag covers your intake. Alan already said he should have checked when he first started the engine but got in a hurry. An alarm would have helped.

If you can hold your hand in the spray and don't have to move it because it is too hot your engine is running at just below the right temp. So you don't need a temperature gauge? Yes you do because you can't keep your hand in the exhaust all the time. You should have an alarm for that too.

Let's see if Alan's engine is ok. Hope so.

JohnL

Kanani · 17-12-2007, 16:16

Quote:

Originally Posted by seafox

Wouldn't say that. Half of the Country are leaving here to go and live in Aussie

Mind you I read that when that happens the average IQ of both Country's increases

Sounds like the same old merry-go-round as when I was there. Are all of the South African's still moving to NZ?

**Ex-Calif** · 17-12-2007, 16:28

Maybe a water pressure sensor with alarm. Even though raw water is very low pressure it could be an option better than a paddle and a switch. Especially teed right after the impeller.

Also the bigger the boat the more remote the exhaust. I can imagine a big center cockpit job having pretty limited visibility to the exhaust.

Water temp won't necessarily go south imediately. There is a closed coolant recirculation system that will stay low temp for a while - especially right after start.

When our impeller went I noticed the exhaust note change and because I am 3 feet from the exhaust port it was easy to verify the failure. Luckily we were 400 meters off the dock but even so we popped the genny and sailed in the last bit as soon as engine room smoke started showing.

Kanani · 17-12-2007, 16:51

Quote:

Originally Posted by Ex-Calif

Maybe a water pressure sensor with alarm. Even though raw water is very low pressure it could be an option better than a paddle and a switch. Especially teed right after the impeller.

Also the bigger the boat the more remote the exhaust. I can imagine a big center cockpit job having pretty limited visibility to the exhaust.

Water temp won't necessarily go south imediately. There is a closed coolant recirculation system that will stay low temp for a while - especially right after start.

When our impeller went I noticed the exhaust note change and because I am 3 feet from the exhaust port it was easy to verify the failure. Luckily we were 400 meters off the dock but even so we popped the genny and sailed in the last bit as soon as engine room smoke started showing.

You're right. On my Passport 45, center-cockpit, we had to lean over the stern and look at the exhaust. If we were in the cockpit, we couldn't hear it at all.

Steve Pope · 17-12-2007, 17:03

I have a small bleed from the exhaust elbow that dribbles onto the cockpit floor which tells me that all is in order, also it lets me know when the salt build in the connection from the salt water cooling circuit into the exhaust elbow is restricting the flow and that it is time to ream out the fitting and increase the flow again.

seafox · 17-12-2007, 19:48

Quote:

Sounds like the same old merry-go-round as when I was there. Are all of the South African's still moving to NZ?

Quite a lot of them lately.

MidLandOne · 17-12-2007, 19:54

Sorry to hear that Alan but you can rest in the knowledge that you are not the first by far to melt a plastic water lift muffler.

We ALWAYS hang the engine key on the seacock for the engine seawater cooling but that not so easy if the seacock is in a not easily accessed place as you say yours is. Even so I have , er um,

, but fortunately only for a very short time.

Centek make very nice water lift mufflers from fire resistant fibreglass which will take such misadventures far better - however I don't know how much they are. Maybe quite a bit more.

PS We are probably heading your way, outer Sounds (based around Ship Cove, Guards Bay, D'Urville), there about last half of January early February.

John

senormechanico · 17-12-2007, 21:48

A 140 F snap switch hose clamped to the downstream side of the raw water injection elbow and tied into your oil pressure alarm will tell you right away if the raw water cooling isn't happening.

Steve B.

seafox · 17-12-2007, 23:02

How is the motor today Alan? I hope we don't have two mates with cracked heads!

**Alan Wheeler** · 17-12-2007, 23:09

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.

seafox · 17-12-2007, 23:18

Why did the water box melt and where did the smoke come from?
It must have been pretty hot?

yachtrodney · 17-12-2007, 23:23

Yes Alan - I can post a Google Earth image if you tell me just where you are - so I can zoom in.

Lat/Long - but just the place names will be OK too

Rodney