2013 Evinrude E-TEC 25 HP – WOT Power Loss

[Mattynp]

Hey everyone! I’m at my wits end with this loss of power at WOT. I think ChatGPT is about to dis-own me! Any help would be greatly appreciated, thank you!

My motor is a 25hp Evinrude E-Tec (E25DTLABA). Tiller with electric start (no key). Has about 335 hours on it. I’ve owned it for about 1.5 years, and am meticulous about flushing it after saltwater use. Worked great for the first year I owned it.

short explanation: at WOT, it’s like the throttle is just getting rolled to idle quickly. No fault lights, motor works fine right after.

Symptoms

• 2013 Evinrude E-TEC 25 HP (E25DTLABA)
• Approximately 335 engine hours
• Starts immediately and idles well.
• Runs perfectly up to about 1/2 throttle all day.
• Under sustained WOT (around 5,500-5,700 RPM), the engine will suddenly lose power as if the throttle was rolled back.
• There is no chugging, misfiring, or shaking when the power drops.
• Brief white steam/vapor appears for a few seconds after the event.
• Engine continues running and immediately operates normally again - no throttle limitation.
• No active fault LEDs are illuminated after WOT loss of power events

Original Failure (July)
Originally the failure was much worse:

• Power loss after only 1-2 minutes at WOT.
• Engine began shaking after loss of power.
• Engine shut down shortly afterward.
• Would not restart for about 30 minutes. Started and operated normally after 30 min cool down. No shakes.
• BRP Diagnostics later showed the engine had entered S.A.F.E. mode due to Code 43 (Engine Temperature Above Range).

Diagnostics

Previous freeze frame for Code 43 recorded:

• Engine Temp: 194°F
• RPM: 5362
• TPS: 95%
• EMM Temp: 93°F

Parts Replaced (all OEM) / Checks Performed

• New OEM water pump kit
• New thermostat
• New pressure relief valve
• New engine temperature sensor
• New high-pressure fuel pump (VST)
• New external fuel line and primer bulb
• New fuel filter
• Fuel tank vent issue corrected
• Intake screens cleaned and installed correctly
• Cooling passages reverse flushed (small sand/sediment only, no impeller pieces or blockage found)
• Repaired leaking EMM cooling hose
• Both spark plugs inspected and look nearly identical with normal appearance
• Thermostat bench-tested in boiling water and operates correctly

Current Status

The problem has improved significantly but still has an intermittent WOT loss of power:

• Originally failed after 1-2 minutes at WOT.
• After repairs, it now runs approximately 25+ minutes of repeated WOT before the same sudden power reduction occurs.
• Fuel Primer bulb is inflated and hard before and after WOT loss of power
• Engine no longer shuts down after WOT loss of power. Motor immediately works 4.0, throttle not limited
• No longer requires a cool-down period before running normally again.

At this point I’m trying to determine whether I’m dealing with:

• a real high-load cooling issue,
• a false temperature indication,
• or something else that only appears after prolonged high-load operation.

Has anyone experienced similar symptoms on an E-TEC?

 

[Mattynp]

UPDATE – September 2026: I think the problem is fixed


Wanted to update this thread in case someone runs into the same problem in the future.


After all of the troubleshooting above, I eventually became convinced this was a cooling-system problem rather than fuel related. The engine had historical high-temperature faults, including Code 43, and the power loss consistently occurred only after sustained higher-RPM operation.


Here is what I ultimately did:

• Replaced the PRV (pressure relief valve) with a new assembly.
• Discovered that the thermostat spring was missing from a previous thermostat replacement and installed the correct spring.
• Removed the thermostat and circulated a 1:1 mixture of RYDLYME Marine and water through the cooling system for approximately 3 hours, using the threaded garden-hose/telltale flush connection and an external pump with the engine OFF.
• Filtered the returning solution. The RYDLYME became cloudy and removed a surprising amount of fine gray/black sediment and debris, even though the thermostat and PRV cavities themselves did not look heavily scaled.
• Thoroughly flushed the engine with fresh water afterward and reassembled the cooling system.

Sea trial result: I ran the engine hard, including more than 30 continuous minutes at WOT, with zero loss of power. It ran perfectly. Previously, sustained WOT would reliably cause the engine to suddenly lose power, so this is by far the best it has run since the problem began.


I can’t say definitively which repair fixed it because I replaced the PRV, installed the missing thermostat spring, and descaled the cooling system at the same time. My suspicion is that the PRV and/or restriction/debris in the cooling passages was responsible for the high-RPM overheating/power loss, while the missing thermostat spring may have contributed to the low-temperature fault I was also seeing.


One issue I’m still investigating: I can still get the low-engine-temperature warning/Code 58 while running on a hose with cold water, even with the thermostat spring installed. However, that did not affect the latest in-water test and the engine performed flawlessly at WOT.


So, at least for now, I believe the original WOT power-loss problem is fixed.


For anyone finding this thread later with a similar E-TEC problem: don’t assume a strong telltale means the entire cooling system is flowing properly. In my case, the engine had a telltale throughout this problem, but flushing/descaling still removed a significant amount of debris from the cooling system.