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Old 08-28-2015, 10:23 AM   #3
C lectric
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City: B.C.
Country: Canada
Vessel Name: Island Pride
Vessel Model: Palmer sedan 32'
Join Date: Oct 2007
Posts: 2,118
It's quite normal for the I.R. gun to not read the same as the guage. It's not in the coolant so there is some heat loss and temp. as it is transmitted to the outside.

The best place to use the gun is at the same place the temp sensor is mounted. Even better is some flat black paint put on the spot you wish to read . The farther the gun is held away the less accurate the reading will be as it will read more of the surrounding area.

Creeping temps are often indicative of a seawater low flow problem:

- R.W. pump needing a proper rebuild from a worn R.W. pump. Old vane pieces from previous failed impellers closing H.E. tubes, Sometimes impellers will take a set and not pump as effectively.

-restrictions from failing hoses especially on the suction side of the R.W. pump,

-ANY air leaks on suction side from loose clamps or hoses, seastrainer gasket failures.

-not fully open seacock valves, clogged through hulls and seacocks from junk or critters,
even the exterior scoop painted closed.

-the heat exchanger tubes can plug from debris over the years. Some times a cleaner such as muritaic acid or Rydlyme can help if the tubes are NOT blocked fully as the solution must pass through. Also impeller bits will not be dissolved, they must be mechaically removed.
David Marchand has written many times about cleaners like this. Look up his threads. I would caution about Yanmars though as they sometime use 'exotic' materials, compared to many engines, which may be damaged.
Also very important to use the CORRECT antifreeze with many Yanmars as the wrong ones can cause trouble.

-The r.w. injection point in the riser can block from rust buildup. Same for the actual shower holes where the R.W. is sprayed into the exhaust stream.

So what temps are you seeing specifically? Where did the temp used to sit? Have you double checked the wiring at the guage and the sender. Voltage off from poor connections will affect the guages ability to read properly.

Can't help with the point where actual damage is done. If what you have now is a slow buildup and then a quick cooldown when the power is reduced back to normal cruise then you MAY be ok to put it off untill the season ends. But that's a three-four thousand mile guess. Just keep an eye on it it if you go that route and watch for the temps to change more rapidly as that will tell you to not put it off longer. Use a marker pen to mark where it is now so there is no memory. Also to mark the high points. If creeping up then get after it.
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