"....My Westerbeke 13A engine overheats after about 20-30 minutes....gets up to 215-225 degrees. Temp comes back down if I let it idle for 10 min....
from this fact you observed that the temp gets up high enough to overheat after 20-30 minutes , i am assuming there is a loss of adequate cooling at the higher engine temps and rpms. the cooling capacity is related to both the amount of cold raw water being pumped thru the raw water pump, and the amount of engine heat that can be transferred to t he r aw water from the antifreeze circulating in t he closed heat-exchanger system. so i assume both t he r aw water pump and impeller, and the fresh water antifreeze pump are functional, and not losing fluid through their weep holes ? . once you've decided that the pumps are functioning as designed, look for why ehat is not properly being carried off by the cooling systems . a scaled up heat exhanger could certainly do this but i would more suspect a piece of raw water pump impeller that is clogging the ht ex tubes. rx is to pull the ht exc run a pipe cleaner or straw thru each hole and be sure no pieces of broken impeller are trapped in there. if your ht ex is clean then look a t possible loss of coolant as a reason why your engine overheats:
-- are you seeing any loss of antifreeze coolant externally ie leak of antifreeze into the bilge from rear ht ex gasket, thermostat gasket, etc ?measure your a/f level, then run your engine to hot and see if you have lost coolant. if you have, that could be the problem.
--are you having to top up the antifreeze more often than usual ??
-----if there is an antifreeze leak in the pressure system of overflow container-radiator--ht ex-- thermostat, you can find a pressure leak with a STANT tester. this is a pressure pump that allows you to pressurize the closed antifreeze system thru the radiator cap. you can pressurize the system without running the engine at all or to hot. you need to get a stant cap that fits the rad cap on your westerbeke.some autoparts store will r ent you 1, i bought one for 445 on the internet..
--- i used the stant to find a very peculiar leak of antifreeze caused by pinholes in my hose loops from the t stat block back into the hot water heater. the hot water heater hoses that carry engine residual heat run from the t stat block back through the hot water htr, to heat the hot water htr water by engine waste heat. both hoses at lower circumference had both abraded on the bulkhead , and both hoses had pinhole leaks that only got serious when the pressure in the system was high, ie after my engine was running at 2800 rpm for 10-15 minutes. the engine temp gauge would be fine then after 10-15 minutes the temp alarm would go off . i could not figure out why. this leak drove me crazy as we could not see any fluid , water or antifreeze, in the engine compartment ( well that was because the antifreeze was draining out on the other side of the bulkhead between engine compartment and water heater, where the hot water hoses came thru the bulkhead . that way the pinhole leaks could drain right into the bilge..unnoticed by me ) .
also check for weeping of antifreeze from the antifreeze (also called) fresh water pump. this pump won't be under pressure from the stant, you could try fixing a colored cloth under it and run the engine to see if a leaky freshwater pump is causing your problem. (dont get the test rag caught in the alt belt or any other moving part...)
if your fresh water antifreeze system checks out, move to t eh r aw water system": assume a good new impeller and good gasket on the raw water pump, and no weeping under the r aw water pump...
-if you have a leak in the raw watersystem, i'd take a colored rag-- like a red shop rag -- and hold it methodically at every joint where raw water could be escaping : (watch for the rag to turn color when wet by water, that is why red is good . ) start at the raw water seacock inlet, go to strainer gasket, bottom of raw water pump especially check at the weephole , up to hose clamps on all hoses into/ out of counterflow part of ht exchanger.
now i have run out of ideas, let us know what you find....
fair winds from the hard at erie PA
