I have a 2004 Four Winns Freedom 180 with a Volvo Penta 4.3GL-D / SX-M. As long as I have owned the boat (about a year now) it has overheated while under load. This overheat condition does not set off the overheat alarm, but shows as 220 degrees on the temp gauge. Inspecting the engine while it is at this temp, the engine is hot but the exhaust manifolds are warm. The circulation hose is hot to the touch, the raw water hose is cold, and the exhaust manifold hoses are warm. The thermostat housing is hot, but I can hold my fingers on it. The temp switch in the thermostat housing is too hot to touch. The temp sender guns at ~200F. If I run it too long, the engine will cycle several times after I turn it off.
Note, when in neutral engine holds at 170 degrees once it is warmed up. I can feel the thermostat turning on by holding my fingers on the circulation side of the thermostat housing, as it cools when the thermostat turns on.
Initially, I brought to a mechanic who replaced the impeller and thermostat. No change. Replaced temp sender. No change. Replaced impeller again. No change. Replaced thermostat again. No change.
Just to be safe, I verified that the temp gauge works properly. I have placed a 55 ohm resistor as a load instead of the temp sender, and the gauge showed about 210 (which I have read is the proper reading for that load)
I have subsequently tried to fix the issue on my own, following the Volvo Penta Gas Engine Overheat Diagnosis Manual. I placed clear hoses with gauges per the instructions. I was not able to see any bubbles in the flow to the raw water pump, from the raw water pump, or to the exhaust manifolds. Gauge readings while on the lake, in neutral at 3000RPM, was -10”hg and 15 psi.
I removed the thermostat housing, removed the drain plugs, and flushed the engine with water for an hour or so. During that time, stuck a zip tie up the drain plugs and moved them around. That increased the flow out the drain plugs. Was able to turn the garden hose about half on and drain plugs would still keep up. Also flushed the other direction, running water into the circulation pump hose. No change.
I then flushed the engine with Rydlyme for 4 hours, and then with water for an additional hour. No change.
I then checked the water inlet system for leaks by disconnecting the raw water pump inlet hose and attaching to a garden hose. Water only exits at the inlet ports, no water exiting anywhere else I could see.
I then flushed the exhaust manifolds with water. Lots of outflow, same on both sides.
So, here are my conclusions thus far:
- Inlet System – no bubbles in any of the clear hoses, no leaks during inlet testing, concluding no leaks in inlet system
- Exhaust Manifolds – manifolds never get hot even when running under load at the lake. Flow seems good and equivalent when flushing. Concluding exhaust manifolds are okay.
- Engine – have taken multiple steps to free flow through the engine. Since none had any effect, assuming flow has always been good through the engine.
One other thing to note, my raw water pump and harmonic balancer vibrate a lot when at idle and low RPMs (see video: https://youtu.be/hrZEjU1sISk).
So, two thoughts, either:
- My raw water pump isn’t pumping enough water. May explain why my 3000RPM suction was -10” instead of -19” (though I’m unsure if that has more to do with me running in neutral at 3000RPM instead of moving). Could this explain why it is vibrating so much? Is the vibration causing it to work less efficiently? How do I fix?
- My engine is out of tune and is just generating more heat that it is supposed to. How do I check this?
Looking for guidance on what to do next.
Thank you for your help.
Note, when in neutral engine holds at 170 degrees once it is warmed up. I can feel the thermostat turning on by holding my fingers on the circulation side of the thermostat housing, as it cools when the thermostat turns on.
Initially, I brought to a mechanic who replaced the impeller and thermostat. No change. Replaced temp sender. No change. Replaced impeller again. No change. Replaced thermostat again. No change.
Just to be safe, I verified that the temp gauge works properly. I have placed a 55 ohm resistor as a load instead of the temp sender, and the gauge showed about 210 (which I have read is the proper reading for that load)
I have subsequently tried to fix the issue on my own, following the Volvo Penta Gas Engine Overheat Diagnosis Manual. I placed clear hoses with gauges per the instructions. I was not able to see any bubbles in the flow to the raw water pump, from the raw water pump, or to the exhaust manifolds. Gauge readings while on the lake, in neutral at 3000RPM, was -10”hg and 15 psi.
I removed the thermostat housing, removed the drain plugs, and flushed the engine with water for an hour or so. During that time, stuck a zip tie up the drain plugs and moved them around. That increased the flow out the drain plugs. Was able to turn the garden hose about half on and drain plugs would still keep up. Also flushed the other direction, running water into the circulation pump hose. No change.
I then flushed the engine with Rydlyme for 4 hours, and then with water for an additional hour. No change.
I then checked the water inlet system for leaks by disconnecting the raw water pump inlet hose and attaching to a garden hose. Water only exits at the inlet ports, no water exiting anywhere else I could see.
I then flushed the exhaust manifolds with water. Lots of outflow, same on both sides.
So, here are my conclusions thus far:
- Inlet System – no bubbles in any of the clear hoses, no leaks during inlet testing, concluding no leaks in inlet system
- Exhaust Manifolds – manifolds never get hot even when running under load at the lake. Flow seems good and equivalent when flushing. Concluding exhaust manifolds are okay.
- Engine – have taken multiple steps to free flow through the engine. Since none had any effect, assuming flow has always been good through the engine.
One other thing to note, my raw water pump and harmonic balancer vibrate a lot when at idle and low RPMs (see video: https://youtu.be/hrZEjU1sISk).
So, two thoughts, either:
- My raw water pump isn’t pumping enough water. May explain why my 3000RPM suction was -10” instead of -19” (though I’m unsure if that has more to do with me running in neutral at 3000RPM instead of moving). Could this explain why it is vibrating so much? Is the vibration causing it to work less efficiently? How do I fix?
- My engine is out of tune and is just generating more heat that it is supposed to. How do I check this?
Looking for guidance on what to do next.
Thank you for your help.