Overheating - Westerbeke 4-91

[painman8629]

Pearson 35, 1978Engine is a Westerbeke "Four 91" (4 cyl, 30 hp). It has a fresh water cooling system that transfers heat to a raw water system.)=====I am having overheating problems at higher RPM's (over 2000)Entire "fresh water system" has been purged with muriatic acid and rinsed.Heat exchanger "tubes" manually cleaned (prior to flush) with a long Teflon rod.The fresh water pump has been removed and is tight and intact. There appears to be excellent "flow" although this is visual and not measured (in GPH). At what RPM should this be checked?There is a "valve" on the top/rear that the manual says can be used to possibly make the engine run hotter/cooler dependent on the climate. Which way does this turn to make it run cooler and what is it physically doing (manual does not state this).Flow through the fresh water system has been checked for continuity with a garden hose. All appears to be clear and free flowing.A new thermostat was checked and opens at proper temp (180) prior to installation.If I run without the thermostat the temp is around 140. (What kind of problems am I likely to incur if I do this? I'm in SW FL and water temps here are very warm in the summer)I've run out of ideas and hoping someone on this list has a few I've overlooked.Thanks in advance,andy paine

 

[Steve Bloomer]

Hose

HAVE YOU CHECKED IF THE WATER HOSE ARE NOT CLASPING WHILE THE ENGINE IS RUNNING. AT TIMES AND AGE THEY DO GET SOFT AND BREAK DOWN.

 

[NYSail]

Mixing elbow

Have you checked the mixing elbow? My new to me Yanmar's was 50% blocked restricting significant water flow and causing the engine to overheat. Have you checked the engine temp. control? On my previous boat (1977 Cal 34 III - still have for sale) it had a Westerbeke 30 that ran hot....Wonder if it had the hot/cooler running control.Greg 1986 P36-2

 

[sailingseadragon]

Check the configuration of your hot water heater..

Many boats with domestic hot water heaters over heat because of their installation..... Westerbeke recommends that the hot water heater not be in series with the expansion tank. See the following linksThis is a link to a discussion on this topic from Pearson 365/367 owners along with other links on the same problem.http://pearson365.com/forum/viewtopic.php?t=31The Scanned Westerbeke Service Bulletin can be found on our web pageGo to "Manuals" then "Westerbeke Water Heater Plumbing Service Bulletin"http://www.sailingseadragon.comGood luckGarner