Author Topic: Identify engine type and Replacing Oil Pressure / Oil temperature sensors  (Read 2833 times)


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Hi everyone,

I recently bought an 8m old fishers boat for cruising the canals of Amsterdam. It's a side project and I have enjoyed working on install a new dashboard and installing an alternator in order to charge the battery.
Installing the Alternator required creating a bracket that holds the alternator in place and creating a custom pulley to drive the alternator from the crank shaft. This works nicely and I'm pretty happy with the result, installing a volt and Ammeter in the dashboard to see the charge / discharge of the alternator / battery.

Next step is to install more instruments to measure the oil pressure and temperature. The question is how to place the sensors?

Engine type
Or actually maybe the first question is - what type of engine is this?

Here are some images:

Alternator install
Final result of installing the alternator and bracket:

New Dashboard column
And here some images of the design of the dashboard column:

How / Where to install the pressure / temp sensors

However what I'm now trying to do is figure out where to put the sensors for the oil pressure and a temperature meter.

I've found this existing bolt that feeds and existing mechanical oil pressure meter (I will be replacing this one with an electrical one):

Threading of this bolt
The outside diameter of the thread is 13.2mm and the inside 11.4 which would lead me to believe it is UNF 1/2-20.
Of course my oil pressure sensor has a 1/8 NPTF thread. As well as a temp sensor would.
I could find a converter bolt that fits the thread in the engine and an NPTF on the other side.

Another interesting thing is that this bolt revealed an inner pressure tube similar to the tube connecting to the oil pressure meter. Can I safely ignore this tube and leave it dangling in the engine?


Open questions:

- Can anyone identify this engine quickly / instantly / easily? (I think it's an SR3M myself but unsure)
- Am I putting the oil pressure sensor at the right place?
- What kind of bolt is that? Is it indeed an R1/2 - 20 UNF bolt?
- What's the function and significance of the inner tube on the inside of the engine?
- Will a connector like this work for me?


Any comments or help greatly appreciated!!
« Last Edit: August 05, 2015, 01:03:22 PM by spif »


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After some more searching I've figured out the thread of the bolt is a normal 1/4 BSP thread which greatly simplifies the search.
All I need now is a 1/4 BSP to 1/8 NPTF adaptor.

Now searching for one like this that will ship to the Netherlands. ;-)


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Yes looks like an SR3. The suffix M marine version typically had an overhead hand starting shaft driving crank sprocket via chain. Click below for Workshop manual download.


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Thanks Richard Hula for the manual. I had actually found that manual before - it's been a great read.

In the end I used some putty to connect the Y-adapter to the existing 1/2 inch bolt already in the engine. The chamber behind that bolt is not under pressure so decided to use the existing piping in stead.

Happy with the result - have all my meters working now:

1. Ammeter
2. Volt meter
3. RPM meter (stationary it's just below 1000rpm - full blast on 2000rpm - but haven't calibrated the gauge yet)
4. Oil Temp (sites between 70 degrees and 110 degrees is on full blast for a while)
5. Oil Pressure (starts at 4 bar but quickly drops to below 1 bar)

So I think I have a problem with the oil pressure - will start to read up possible causes for this.