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Old 03-20-2016, 12:23 PM   #1
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Laser Targets

For those that use a laser IR gun underway: What items do you check and exactly where do you check them? For example: oil temp at the pan.

Extra points for any specific suggestions for a Yanmar 370 w/ZF-Hurth.


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Old 03-20-2016, 12:31 PM   #2
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I don't remember where I got this list, maybe TF:

Alternator: Wave the IR pyrometer around the alternator case while holding the trigger, use the highest reading.

Exhaust, dry and wet: No part of the exhaust system that can be touched should exceed 200°F. Ideally, the wet portion, the parts that rely on hose and fiberglass pipe, shouldn’t exceed 160°F. Use the same scanning technique as you would with the alternator, looking for the highest temperature.

Stuffing box: For both conventional and dripless, scan the stuffing box as well as the cutless bearing if one is installed in the shaft log just aft of the stuffing box. The temperature shouldn’t exceed 30°F above the temperature through which the vessel is moving.

Coolant expansion tank (where the pressure cap is located):
The temperature should be very close to that shown on your dashboard instrumentation, if it isn’t, there’s
a problem.

Oil pan: Measure temperature at the vertical halfway mark on the side of the pan; ideal oil temperature is between 180°F and 220°F.

Thrust bearing, if equipped: Each manufacturer has its own protocol for maximum allowable temperature. Generally, anything over 165°F is an indication of a problem.

Finally, engine room checks aren’t very useful if they aren’t carried out regularly. While you can’t check this space too often, doing so once every hour or two makes it likely that you’ll identify problems before they become critical.

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Old 03-20-2016, 01:59 PM   #3
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I have the Yanmar 6LY.

The thermostat housing is a better place to check coolant temperature on that engine. It will read about 5 degrees less than the coolant due to heat transfer losses. After I see how the water temp gauge is calibrated, I rely on that.

The oil pan is hard to get to so I just shoot the oil filter.

I check the exhaust right after the mixer. Usually runs 100-120 degrees.

I don't do these regularly, maybe once a year. Otherwise I just use my hand on the oil filter and exhaust mixer to see if all is ok after 15 minutes at cruise power after everything has warmed up. After that I will just look at the engine every few hours for smoke, leaks, etc.

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Old 03-20-2016, 03:35 PM   #4
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I just listed mine on the engine room check thread. Looking for variances from baseline readings and/or engine specs, as well as variance to gauges.

"There's the Right Way, the Wrong Way, and what some guy says he's gotten away with"
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Old 03-20-2016, 03:54 PM   #5
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I haven't done it on the new boat yet, but I saw in an article in PM mag one time to take a paint pen with you and put a dot or circle on the spot you check so you can hit the same spot every time and get accurate and consistent data to see trends and variances over several months or years. I think Steve D'Antonio may have authored the piece.
2000 Navigator 4200 Classic
(NOT a trawler)
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Old 03-20-2016, 04:05 PM   #6
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Keep in mind that various surfaces have different emissivities, and that affects IR radiation from that surface. IR gun feeds of IR radiation, so it matters. Shiny SS or Al will not give a good reading on the gun. Most painted surfaces are ok.
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Old 03-21-2016, 06:28 AM   #7
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Very helpful - thanks all.
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Old 03-21-2016, 07:51 AM   #8
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One thing to watch out for with laser temp guns is that the area sensed is much larger than the laser dot, especially as the gun gets further from the target. On the side of the gun or in the instructions it will tell/show you how wide the sensing area is at different distances from the target. The bottom line is that you want to get the gun as close to the target as possible, otherwise you are likely sensing the average temp of a much larger area than you might thing.

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