Ask Captain Chris – About Your Below Deck Systems

Photo tachometer

Ask Captain Chris – About Temperature Guns and More

Even after you own your boat you may need a little help with your onboard Below Deck Systems. In addition to joining us at a scheduled seminar, we can also do a virtual walk-through in your engine space. This boat owner took some time to process the new information he learned and reached out by email for follow up.

Hi Captain Chris,

You did a zoom walk-through for me a couple years ago on my Cummins BT6.9 330 engines. I suspect my Faria gauges at the helm are no longer accurate (I have heard throughout the years that they aren’t the best). I want to measure my engines running temp and also their RPMs at speed.  For temp, the consensus seems to be point a temp gun-would I do that on the cylinder heads to get the best reading?

For RPMs, I have no idea.  Any advice you have would be appreciated!

Kind regards,  Dave B


The Answers and Solutions are Simple:

First use an IR thermal thermometer and aim the beam at the fitting where the thermal sensor sends the information to your dashboard instruments. Compare the two readings. If they differ a lot then presently you may operate the boat with the mental understanding the temperature reading differences.

RPMs. Use a handheld Photo Tachometer. Tape a reflective patch on the front crankshaft pulley (harmonic balancer) and ask a helper to control the throttle. Using the Photo Tach increase the engine RPMs to a nice even number like 650 or 700. Watch that RPM to make sure the engine is settled at that RPM then compare that reading to the dashboard gauge.

Some Tachometers have a set screw hidden in the back of the instrument and you will need a long plastic tiny screwdriver known as a “tweeker” to adjust the tach up or down. If you have an “all in one” gauge cluster and cannot make that adjustment then the only solution is to purchase a new instrument cluster, oil, temp battery voltage, hour meter and RPMs.

Hope this helps, Chris

Want to Attend a Seminar?

Click here to check out our upcoming seminars for Introduction to Boat Systems and Cruising 101 FUNdamentals. Or Ask Captain Chris to do a virtual walk-through in your onboard below deck spaces. 772-205-1859 or to set up a private consultation.