I’ve tried everything I can think of. The details-
W40(Perkins 4-107) 2200 hours in a Niagara 35
Previous owner of 10 years proudly told me he never ran the engine
above 1800rpm which he thought was a good idea so the engine
has most likely been chronically under loaded for years. Surveyor
fell in love with the boat
during the survey
and decided it was perfect so didn’t check basic things like batteries
(all dry and ruined) or engine temp. I discovered the 90* raw water elbow
at the exhaust elbow
was almost completely blocked which tells me the engine had most likely been overheating
for a long time.
under load above approximately 2000rpm. Temp increases with rpm
circuit cleaned out. New water
cooler, heat exchanger
cooler and v-drive cooler all checked. All new hoses. Exhaust
elbow removed and checked for obstructions. Raw water intake increased in size from 1/2” to 1”.
states the exhaust should be 2” all the way back. Mine is 2” from exhaust elbow to muffler
then 1.5” from there. The transom fitting is 1.5” and looks original from 1979 so this was the factory installation
Fresh water circuit-
All hoses replaced.
I discovered this past week that the coolant
pressure cap was rated at 4psi and Westerbeke says it should be 15psi. I pressure tested the 4psi cap and it couldn’t hold any pressure. Replaced with a 15psi cap and pressure tested the system. Pressure drops slightly then levels off for hours. Tightened all hose clamps. Tightened the fresh water pump/alternator belt.
shows a 30F drop in temp between inlet and outlet of coolant
installed in system a few years ago. Originally I installed it in series as Westerbeke explicitly says to do. This does not work
nor does it make sense. Now it is installed in parallel. Feed is from the coolant alarm
sender port on the head
which is reduced from 1/2npt to 1/8npt to reduce flow to the water heater
and return is to the heat exchanger. There is a shutoff valve in the feed line so I can remove the water heater from the circuit for testing purposes and it doesn’t seem to make any difference.
Air filter was cleaned out. Sea strainer has been cleaned repeatedly. I’m at a complete loss. Nothing I do seems to make any difference. Temperature is being taken at the thermostat (also replaced) with an infrared temp sensor as well as the engine sensor (also replaced).
Sorry for the long post but this has been 3 years of dealing with this and I’m desperate. I’ve been told the cooling
system on these engines is marginal to begin with so I’m not expecting perfection. I realize there are many, many reasons for an engine to overheat but I feel like I’ve exhausted most of the possibilities. Any help would be greatly appreciated.