I’ve tried everything I can think of. The details-
1979
Westerbeke 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.
Overheating under load above approximately 2000rpm. Temp increases with
rpm increase.
Things done/replaced-
Raw water circuit cleaned out. New
water pump">raw
water pump.
Oil cooler,
heat exchanger,
transmission 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”.
Westerbeke 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.
Heat exchanger shows a 30F drop in temp between inlet and outlet of
coolant circuit.
Water
heater 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.
Dylan