Yanmar 4JH3-TE re-wiring

[Sevellyn]

Good Morning,

I recently purchased a 1984 Nauticat with a Yanmar engine - not the original engine and she has 35 years of wiring and re-wiring under her, so things are a bit of a mess. I seem to have two of everything and I can't figure out how to put it back together.

For example I have two temperature sensors in the attached photo - yellow wire goes to the pilothouse engine panel, white (with the fancy duct tape tag) goes to the on-deck engine panel. Same goes for oil pressure, there seems to be an add-on sensor next to the filter that goes to the main panel and then the image below of the original sensor that went aft.

Do I need both? Can I abandon one of these?



Thanks for your help in advance!

[ScottRhodes13]

A couple things come to mind:

The different temperature sensors might be specific to the different gauges.

Regarding the oil pressure sensors -- my 4jh2 has two oil pressure sensors. The sensor near the oil filter connects to the oil pressure gauge. It measures the oil pressure before the oil enters the gallery and should read around 60 - 80 psi. There is another sensor located on the block that connects to the oil pressure light and buzzer. It measures oil pressure after the gallery, just before it returns to the oil pan, and sounds the buzzer if the pressure is under about 4 psi.

[Wotname]

I would expect you should find both a temperature sensor (used with a temperature gauge) and an over-temperature switch (used for a warning light and/or audile alarm).

Similarly for the oil pressure - one for a gauge and one for an alarm.

[Sevellyn]

Interesting - makes me wonder why those items weren't hooked up to any alarms in the primary navigation station in the pilot house, but now that I know what they are for I can correct that.

thank you both for your insight!

[tkeithlu]

While the gauge/alarm set up is as expected, your description sounds like the two sensors feed two gauges, one below deck and one at the helm. That doesn't make as much sense, but could be the case, given we cannot probe the mind of each former owner.