SVTatia, When someone goes to visit a doctor for a checkup, the physician usually starts with recording aspects of the patient's current
condition to help establish a baseline. Each of us is slightly different from another, but we all exhibit changes according to our personal baseline when we are undergoing stress or disease. So, the idea is to begin recording things when we are feeling "normal", and comparing things when we are not. Whether it's blood pressure, blood chemistry, body temperature, heart rate, or whatever, it's very helpful to a medical
professional (and ourselves) to know what is our personal "normal" and what is not.
I like to keep aware of several critical factors. If I shoot the heat gun laser beam on the seawater intake valve, I have a pretty good idea of the current water
temperature. After running the engine for a few minutes, at idle and neutral, I can take a look at the cooling
water temperatures at several points along the pathway: at the saltwater impeller casing, at the water temp sensor, the heat exchanger
casing, and the inlet to the exhaust manifold, as well as the outlet side, a couple inches away (or even the exhaust hose. This gives me the basic info to know what is happening under no load conditions, how efficiently the heat exchanger
is doing its work, and how well the exhaust/seawater mixer is doing its thing.
Then, with the dock
lines secured, run the boat in forward gear
at about normal low idle speed for ten minutes. Take the range of temps and record
them. Increase the speed to normal cruising RPMs and do the same. You can also record
this static test at higher RPMs if you trust your dock cleats
. Then take the boat out for a spin and get the same range of temp testings.
If, over time, with similar seawater temperatures, you notice that the temperature is rising significantly, especially at the temp sensor, the inlet to the exhaust mixer and the exhaust hose at the connection to the mixer, you might want to consider further examination of the possible causes: an impeller that is starting to go bad, issues with the heat exchanger, or possible blocking of the exhaust elbow
by corrosion. This gives you an easy way to regularly check the engine's performance, based on temperature data. I also record temperature at a number of other spots, just because I'm curious. These include the alternator
case, the transmission
box, the injectors, the shaft log, and shaft bearings. Think, anything that might go bad, will, especially if you aren't paying attention to them. Heat guns
are relatively cheap
and provide a great deal of info, but only if they are used in a regular and consistent manner, and the results are recorded. I like to keep mine in the engine maintenance
log for future playing around with on the Excel program. You can have a ball making charts
that might be very useful when discussing performance with your mechanic.