Tell tale on an inboard?

alt · 20 September 2006, 13:56

I have a Mercruiser 1.7 diesel inboard with an Alpha one Leg

My main concern is that I am always paranoid that the raw water system may not be pumping (Although I know it is, as the engine never overheats). It's just paranoia I know, but when I had an outboard I had the re-assurance of being able to see a tell tale p1ssing out the back

Is there a mod available to install a tell tale on an inboard engine?

Erin · 20 September 2006, 15:02

Not as far as I know. However, you can normally fit a heat sensor with alarm onto the exhaust pipe which gets suddenly very hot if the raw water is not being expelled into the exhaust elbow. (Assuming a sterndrive works the same as a shaft drive engine with raw water injection into the exhaust).

SDGANDER · 20 September 2006, 16:22

We ve got one on our Mercruiser with a leg..

I m can't remember where the take off is thou - will look next time I m on the boat.

SDG

Andy Gee · 20 September 2006, 17:16

Is there not one already fitted, usually a flow alarm as opposed to a tell tale.
Andy

alt · 21 September 2006, 09:05

Quote:

Originally Posted by Andy Gee

Is there not one already fitted, usually a flow alarm as opposed to a tell tale.
Andy

I have a temp gauge for the enclosed water system

Andy Gee · 21 September 2006, 10:11

Quote:

Originally Posted by alt

I have a temp gauge for the enclosed water system

Do you not have a "Low Water Flow" type warning light on the panel?
cheers
Andy

alt · 21 September 2006, 11:24

Quote:

Originally Posted by Andy Gee

Do you not have a "Low Water Flow" type warning light on the panel?
cheers
Andy

Nope, the closest thing I have is "Water in fuel" ... nothing else to do with water

Nos4r2 · 21 September 2006, 18:56

Is the water pressure from the impeller high enough for you fit a water pressure gauge to the raw water side of the cooling system?

SDGANDER · 23 September 2006, 09:15

Right, finally had a look at ours - fitted to a Delta.

There is a take off from the front of the thermostat housing which has a pipe running to a skin fitting on the transom, The pipe diameter is about 5 mm.

I m not sure if this is an add on or a Delta modification or company spec.

SDG.

alt · 23 September 2006, 10:16

Quote:

Originally Posted by SDGANDER

Right, finally had a look at ours - fitted to a Delta.

There is a take off from the front of the thermostat housing which has a pipe running to a skin fitting on the transom, The pipe diameter is about 5 mm.

I m not sure if this is an add on or a Delta modification or company spec.

SDG.

Thanks for that, i'll look into it. I don't want to just throw a pipe on in fear of taking away too much water pressure from the raw cooling system

jwalker · 23 September 2006, 14:43

Quote:

Originally Posted by SDGANDER

....There is a take off from the front of the thermostat housing which has a pipe running to a skin fitting on the transom, The pipe diameter is about 5 mm.

Unless your engine is running on direct raw water cooling, the thermostat will be on the closed engine cooling circuit.

SDGANDER · 23 September 2006, 18:47

Quote:

Unless your engine is running on direct raw water cooling, the thermostat will be on the closed engine cooling circuit.

Thats a fair point - it runs as soon as the engine is started. I m not at the boat now but the more I think about it, it has to be the heat exchanger feed - although I looked at the engine manual to see if the modification was in there (its not) and the diagram showed the take off point as the thermostat housing...

SDG

alt · 23 September 2006, 23:17

Quote:

Originally Posted by jwalker

Unless your engine is running on direct raw water cooling, the thermostat will be on the closed engine cooling circuit.

That is a good point. My water temp is taken from the enclosed cooling system. I'm going to do a little research online, if I find anything of interest I will let ye know!

jwalker · 23 September 2006, 23:31

I use a temperature sensor on the exhaust a short distance below the water injection point. The temperature at that point is always around 60°c. If there was no water, I'd expect that to be closer to 600°c. I have set the alarm at 90°c and I don't expect there to be much of a delay before that temperature is reached if the water flow stops. A tell-tail is unlikely to give you sufficient warning unless you are constantly watching it. Just my opinion, of course.

Nos4r2 · 24 September 2006, 08:25

Quote:

Originally Posted by jwalker

I use a temperature sensor on the exhaust a short distance below the water injection point. The temperature at that point is always around 60°c. If there was no water, I'd expect that to be closer to 600°c. I have set the alarm at 90°c and I don't expect there to be much of a delay before that temperature is reached if the water flow stops. A tell-tail is unlikely to give you sufficient warning unless you are constantly watching it. Just my opinion, of course.

With temps like that theory says you could simply clamp an overheat sensor from a mariner 2-stroke to the exhaust in the same place then-cheap and simple. They trigger at a bit over 100 degrees C. All you'd need is an alarm beeper and a switch hooked to the ignition so it was live when it's turned on.

alt · 24 September 2006, 10:39

Great ideas guys - Something to keep me busy over the winter months!

jwalker · 24 September 2006, 11:20

Quote:

Originally Posted by Nos4r2

....you could simply clamp an overheat sensor from a mariner 2-stroke to the exhaust in the same place then-cheap and simple.

Yep, temp sensors are freely available and cheap and a wee circuit easy to make.

However, a temp gauge linked to an exhaust sensor gives a bit of indication of how hard you are running the engine. It can cheat you though if the engine gives a rich mixture at full throttle cos the excess fuel lowers the exhaust temp.

I use a combined turbo boost/temp gauge. The boost tells me how hard I'm running the motor and the gauge keeps a eye on the exhaust temp. It has settable alarms. The down side is, it's not cheap.

SDGANDER · 27 September 2006, 15:21

Took these photos today of ours. This is the fwd end and portside of the engine. The tell tell pipe is obviously the smaller pipe from the brass fitting.

Andy Gee · 27 September 2006, 15:54

Quote:

Originally Posted by SDGANDER

Took these photos today of ours. This is the fwd end and portside of the engine. The tell tell pipe is obviously the smaller pipe from the brass fitting.

I would have thought that the telltale would be better coming from the discharge side to ensure that the raw water is actually circulating the engine.
Not being familiar with these engine, would it be possible to take one from the discharge side, perhaps using a plastic straight through pipe coupler, the one with the small screw blank?
Andy

alt · 27 September 2006, 16:39

Quote:

Originally Posted by SDGANDER

Took these photos today of ours. This is the fwd end and portside of the engine. The tell tell pipe is obviously the smaller pipe from the brass fitting.

Very interesting! What sort of pressure is the raw water under? ie. how far out that pipe does water shoot? Did you do that mod yourself?