Hierarchy of Engine Instrumentation

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
jimh
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Hierarchy of Engine Instrumentation

Postby jimh » Wed Nov 01, 2017 9:32 am

For the purpose of this discussion, let's assume that the FIRST engine gauge needed is a tachometer. Okay, what comes next?

Choose from:

--engine temperature gauge

--engine cooling water pressure gauge

--engine alternator or engine battery voltmeter

--engine trim position indicator

On my boat, I have dedicated individual gauges for all five functions.

Jefecinco
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Re: Hierarchy of Engine Instrumentation

Postby Jefecinco » Wed Nov 01, 2017 7:40 pm

For me:

Delete the engine temperature gauge. Cooling water pressure tells me all I feel I need to know about engine cooling system performance. Our SmartCraft system includes engine temperature but I very seldom check it.

Keep the engine cooling water pressure gauge for the above reason.

Keep the engine battery voltmeter as it reads battery voltage when the engine is not running and alternator voltage when the engine is running (or so I'm told).

Delete the engine trim position indicator. The engine tachometer tells me all I care to know about engine trim.

I could do without the engine cooling water pressure gauge but believe it is good information to have. An acceptable substitute would be a low engine cooling water pressure audible alarm.

When I was training as a power plant control room operator I soon learned that most of the displayed data was virtually useless unless troubleshooting a malfunction. You quickly learn which gauges matter and which don't. In general, non critical alarms can be silenced by the operartor. Critical alarms require attention and only the plant superintendent can silence them.
Butch

InVision
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Re: Hierarchy of Engine Instrumentation

Postby InVision » Thu Nov 02, 2017 5:01 am

I respectfully disagree about engine temp gauge. Here, in salt water conditions, water passages in the engine can get clogged. A temperature gauge is useful if pressure is normal but the engine runs hotter than normal.
Proud owner of 2004 Boston Whaler 190 Nantucket ! ;)

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Jefecinco
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Re: Hierarchy of Engine Instrumentation

Postby Jefecinco » Thu Nov 02, 2017 9:27 am

There is nothing wrong with having an engine cooling water temperature indicator if you find the information useful. The reason I don't place much value on the information is that if cooling water pressure is normal an engine is very unlikely to overheat. High pressure can indicate an obstruction to flow which may cause over heating requiring prompt attention. Low pressure is often indicative of a worn water pump impeller. A sudden drop in pressure can indicate very low or no pressure normally caused by something covering the cooling water inlet in the lower unit.

Salt deposits in cooling water passageways is caused by an over heated engine.
Butch

jimh
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Re: Hierarchy of Engine Instrumentation

Postby jimh » Thu Nov 02, 2017 9:37 am

Most outboard engine temperature gauges show the temperature of some part of the engine block, not the temperature of the cooling water. Usually the cooling water temperature is just warm, and never reaches the actual temperature of the engine block. The engine temperature sensors are usually in the engine block cylinder heads.

On my modern V6 engine there are two engine temperature sensors, one for each side of the V-block. These sensors are read by the engine management module (EMM), which sends the engine temperature data as part of its engine parameter NMEA-2000 datagram.

If conventional instrumentation is used, there are two pre-threaded bosses on the engine block where a conventional gauge's temperature sensor can be threaded into the cylinder head area. Typically only one sensor would be installed, and it would go on the side of the block with the highest cylinder location.

conch
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Re: Hierarchy of Engine Instrumentation

Postby conch » Sat Nov 04, 2017 1:08 pm

I do not see it listed as a choice, but I have to say it is my OIL PRESSURE gauges.

Chuck

jimh
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Re: Hierarchy of Engine Instrumentation

Postby jimh » Sat Nov 04, 2017 1:24 pm

CHUCK--I guess my bias toward outboard engines being two-stroke-power-cycle engines and not having an oil sump with recirculating oil under pressure was showing. Certainly on an engine that depends on oil being re-circulated under pressure by a pump, monitoring the oil pressure on a gauge is a good idea. I would suspect, however, that your engine probably monitors oil pressure with a sensor and sounds an aural alert to indicate loss of oil pressure.

Vance's Revenge
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Re: Hierarchy of Engine Instrumentation

Postby Vance's Revenge » Sun Nov 05, 2017 2:48 am

I run all of those gauges and more. Never rely on a warning horn that comes on too late because I have an older two stroke and run in sand a lot. I have a water pressure gauge and a temperature gauge sender at the top of each cylinder head. A single cylinder-head gauge only reads off of the one head. If sand or something else were to be sucked into the motor and clog a thermostat on the opposite side you wouldn't know it. A left bank temperature gauge next to a right bank temperature gauge along with the water pressure gauge under them makes for a nice way of knowing exactly what's going on at a quick glance at the dash. Great piece of mind and easy to install for not much money. I'm very glad I did it.--Vance