Honda BF225 Stalls over 4,000 RPM

2004 Honda 225, if cruising around 4,500 RPMs, after a few minutes the engine stalls. Red over heat light comes on, sounds once. Turn key off, restart and can immediately cruse at 3,900 RPMs for the rest of the day.

High and low Pressure filters are new, no change.

I've seen some similar threads on this, and most do not say what fixed their issue.

I've seen suggestions on VST, HP pump, water return tubes on exhaust manifold, IAB intake air bypass solenoid, clogged fuel injectors. Without throwing parts at it, has someone had this issue with a known fix?

If your red light is coming on, it is an indication of overheat. Typically causes for overheat are....bad water pump; stuck thermostats; partially clogged cooling system; clogged intake ports; or clogged bypasses.

It is also possible that the motor is mounted too high or trimmed too high and not picking up enough water....but I have to assume that the motor worked ok on this boat in the past, so the height would not be an issue.

Basically, the engine is not getting enough water through the motor to cool properly. When you try to work that engine hard, it goes into a safe mode and shuts down. It is probably getting just enough water flow to cool at the lower speeds.

Easiest thing to do is to pull the thermostats and see what they look like and what the thermostat housing looks like. Put a hose up to the hose at the thermostat and make sure that there is good flow out of the exhaust (prop). If the thermostats are coated with debris or the housing looks somewhat clogged, you are probably finding the issue. If there is not good flow out through those hoses, then it is time to check the bypasses and exhaust areas.

If all that is clear, then pull the lower unit and change the water pump. While the lower unit is off, backflush the motor from the thermostat housings with a hose to see it there is any loose debris in the system, like pieces of impeller. You can also backflush using the flush port, but be sure to also do it from the thermostats. When you backflush, put a 5 gallon bucket under the motor to catch the water and potential debris so you can see what, if anything, is in there.


Mike

To clarify, this is on a world cat with twin bf225s.

Both water pumps/impellers were changed, however. The port motor that is shutting down has 20 psi of water pressure and has a strong stream of water at idle.
The starbard motor has closer to 10 psi of water pressure and noticeably less pressure coming out at idle, but the starboard motor is not having any issues, no alarms, nothing.

I'll check the thermostats, back flush, and while I'm at it, change some of the exhaust manifold coolant lines. Looking at the exhaust manifold thermostat schematic for the 2004 225 I'm seeing small water lines #6,7,8,&9 and I'll order thermostats and o rings. Anything else?