We took Rachel’s sister and her husband out for their first sail. It was partly cloudy and rained a bit. The wind died off near Blakely Rock and after sailing without much result we fired the iron genny back up.

AFD – 5:00 HOURS
15.1 NM

I did a bit of diagnosing of the temperature fluctuations. I found some reference to Volvo changing the thermostat and that the original actually had a hole in it that allow for some bypass of the thermostat. So under the guidance of the internet I drilled a 1/8” hole through the body of the thermostat. After the engine had been running about an hour at 1700RPM, the bobbing of the temp gauge had stopped, but it was sitting in the green, just shy of the redline. I measured the temperature using my infrared thermometer at the following:

Fore cylinder top 170º F
Aft cylinder top 130º F
Front of block at flywheel junction 220º F
Manifold at thermostat 145º F

So my observations lead me to the follow conclusions: the bouncing seems to have gone away; it seems to be running hotter than previous years; the front cylinder probably has a partial blockage in one of the cooling runs.

My thoughts are like this.

  • I’m going to drill the hole out larger to 3/16” essentially doubling the area of the hole.
  • At some point I’m going to need to clean the cooling channels on the cylinder.
  • There is probably nothing blocking the cooling lines downstream of the thermostat.
  • The muffler is probably operating as normal.