Brian Demo
New member
2012 Hurricane SD2400
Mercury MerCruiser 350 Mag
Engine: 2A030645
Transom: 2A024601
Drive: 2A019455
Problem: Port side of engine is overheating 3x that of Starboard
Water Pressure dropping 3psi to 1 psi
(Issue started with Starboard side overheating. Replaced manifold and riser, then port side started overheating. Replaced port side manifold and riser and still overheating.) No water getting to port side.
Correction/Inspections:
Not impeller-replaced
Not thermostat-replaced
Not inlet hoses- checked for clogs
New manifolds and risers replaced on port and starboard side
Possible causes found in forums……
#1 Lower unit
Bravoitis…….where the engine draws in it's water supply. The grommet in the trans plate that transfers water from the outside hose to the inside hose get worn and collapses.
(I exclude this as the cause because no water is getting to port side even at idle)
#2 Bypass Issue
The 350 has a problem with the bypass. Occasionally, too much water goes through the bypass and not enough to the engine to cool it. Apparently, they put a little restricter in at the bypass to force more water in the engine cooling hose. This fix is a plastic washer (restricter) that is placed at the "Y"at the bypass to force more water through the motor for cooling. Though this is not done on all boats. Only on the ones that seem to have a random over heating problem. This plastic diverter if broken or not installed correctly will allow most of your water to run out the exhaust and not thru the block. After reading this to my mechanic, we decided to insert a 1" stainless fender washer with a 1/4" hole in the hose to the left riser. It fixed the problem! Risers are staying cool and the engine temp is normal!
#3 Two T-fittings
Allows water to drain or circulate water from the exhaust manifolds to the block. These T-fittings are fitted to the newer (2005-ish and up) 350 exhaust manifolds. They allow water to circulate through the heads and the block. There is a valve in these fittings that is not on earlier versions of the 350. The valve opens to allow water to be drained from the manifolds for ease in winterizing. The valves remain open by pressure from the water pumps.
#4 Air Leak
Checking the blue drain, may be an air leak, perhaps in more than one place.
REPAIR HISTORY
Guardian Activated- Overheat fault code
Replace pump impeller and plates
Inspect poppet valve and all hoses
Guardian Activated- Overheat code 321, 322 fuel trim
Replace thermostat
Guardian Activated- Overheat code 321, 322
Starboard manifold running hot, 02 sensor rich and lean-may need o2 sensor
Code for low 02 input on both banks, Starboard manifold running hot,
TSB- Paint and debris found in fuel pressure regulator, Install new regulator and remove/flush fuel line from assembly to Fuel rail
Guardian Activated-
Flush hoses and replace thermostat and poppit valve
Guardian Activated-
Replace starboard manifold and riser
Guardian Activated-port side running hot, low water pressure
Sea water pump and impeller was worn and replaced (impeller was replaced 2 months ago)
Inspected water intake hose (apparently this is a known issue with hose collapsing) does not appear to be collapsing…but did not pull engine and separate transom
Seal was broken upper drive bolts to bell housing, replace seal kit and added sealer around intake
Removed all of the hoses from the engine blown thru them and back flushed the intake hose that the service bulletin talks about. Mercury tech service reps. also agree that the port side manifold is the issue. If the problem was being caused by the intake water being restricted then why wouldn’t both manifolds be overheating. You only have 1 water intake supplying water to both manifolds but only 1 manifold is overheating?? One of the test the factory offered was to remove the exhaust temp sensors from the elbows and then crank the engine. When we did that the stbd. side manifold had a solid stream of water coming from the elbow. When we did it on the port side elbow we just had a trickle of water coming out.
Port side manifold and riser replaced
Guardian Activated- Port side manifold 3x hotter than starboard side.
no water getting to port side at all.
Any advice is greatly appreciated.
Mercury MerCruiser 350 Mag
Engine: 2A030645
Transom: 2A024601
Drive: 2A019455
Problem: Port side of engine is overheating 3x that of Starboard
Water Pressure dropping 3psi to 1 psi
(Issue started with Starboard side overheating. Replaced manifold and riser, then port side started overheating. Replaced port side manifold and riser and still overheating.) No water getting to port side.
Correction/Inspections:
Not impeller-replaced
Not thermostat-replaced
Not inlet hoses- checked for clogs
New manifolds and risers replaced on port and starboard side
Possible causes found in forums……
#1 Lower unit
Bravoitis…….where the engine draws in it's water supply. The grommet in the trans plate that transfers water from the outside hose to the inside hose get worn and collapses.
(I exclude this as the cause because no water is getting to port side even at idle)
#2 Bypass Issue
The 350 has a problem with the bypass. Occasionally, too much water goes through the bypass and not enough to the engine to cool it. Apparently, they put a little restricter in at the bypass to force more water in the engine cooling hose. This fix is a plastic washer (restricter) that is placed at the "Y"at the bypass to force more water through the motor for cooling. Though this is not done on all boats. Only on the ones that seem to have a random over heating problem. This plastic diverter if broken or not installed correctly will allow most of your water to run out the exhaust and not thru the block. After reading this to my mechanic, we decided to insert a 1" stainless fender washer with a 1/4" hole in the hose to the left riser. It fixed the problem! Risers are staying cool and the engine temp is normal!
#3 Two T-fittings
Allows water to drain or circulate water from the exhaust manifolds to the block. These T-fittings are fitted to the newer (2005-ish and up) 350 exhaust manifolds. They allow water to circulate through the heads and the block. There is a valve in these fittings that is not on earlier versions of the 350. The valve opens to allow water to be drained from the manifolds for ease in winterizing. The valves remain open by pressure from the water pumps.
#4 Air Leak
Checking the blue drain, may be an air leak, perhaps in more than one place.
REPAIR HISTORY
Guardian Activated- Overheat fault code
Replace pump impeller and plates
Inspect poppet valve and all hoses
Guardian Activated- Overheat code 321, 322 fuel trim
Replace thermostat
Guardian Activated- Overheat code 321, 322
Starboard manifold running hot, 02 sensor rich and lean-may need o2 sensor
Code for low 02 input on both banks, Starboard manifold running hot,
TSB- Paint and debris found in fuel pressure regulator, Install new regulator and remove/flush fuel line from assembly to Fuel rail
Guardian Activated-
Flush hoses and replace thermostat and poppit valve
Guardian Activated-
Replace starboard manifold and riser
Guardian Activated-port side running hot, low water pressure
Sea water pump and impeller was worn and replaced (impeller was replaced 2 months ago)
Inspected water intake hose (apparently this is a known issue with hose collapsing) does not appear to be collapsing…but did not pull engine and separate transom
Seal was broken upper drive bolts to bell housing, replace seal kit and added sealer around intake
Removed all of the hoses from the engine blown thru them and back flushed the intake hose that the service bulletin talks about. Mercury tech service reps. also agree that the port side manifold is the issue. If the problem was being caused by the intake water being restricted then why wouldn’t both manifolds be overheating. You only have 1 water intake supplying water to both manifolds but only 1 manifold is overheating?? One of the test the factory offered was to remove the exhaust temp sensors from the elbows and then crank the engine. When we did that the stbd. side manifold had a solid stream of water coming from the elbow. When we did it on the port side elbow we just had a trickle of water coming out.
Port side manifold and riser replaced
Guardian Activated- Port side manifold 3x hotter than starboard side.
no water getting to port side at all.
Any advice is greatly appreciated.
