Intermitent overheat warning F225TXRB

[jercat]

Hi, I have one of my engines a 2003 four stroke 225HP that the overheat alarm turns on after 2 to 3 hours of *****ing in open sea. I turned it off/on for 10-20 seconds and then I continued for more than five hours with no warning alarm or heat indicator in the gauge.

I also had the problem at the dock with the engine cold and I did the same thing turn it off/on and continue for my fishing day. The engine has 500hrs. I changed the impeller using the Yamaha kit and also replaced the thermostats which looked a little bit rusted but they were working ok. The tell tale water stream looks fine. The engines are used in salt water and flushed with fresh water for several minutes after each use.

I have no clue what else to look for and any help will be appreciated.

[jercat]

Any ideas guys? Please, I need help!!!!

[Reel Insane]

First of all having a good stream at the tell tale only indicates good water pressure to the base of the engine. Check your exhaust for good water flow and see how hot it is getting. Corrosion inside the engine can also reduce water flow. Using salt away or other similar products can reduce salt deposits and keep corrosion at bay.

Also, if you have a laser thermometer you can check the temperature of the engine at several spots on the cylinder head. This will allow you to take an average to see if one cylinder head is getting hotter than the other. This would be indicative to a blockage or restriction somewhere in that region.

But:

It sounds like you have an electrical issue.
I am not there to see what is happening, but if you can turn the engine off and immediately back on again (within 30 seconds) and it runs fine for the rest of the day sounds like a wire issue.

I would pull the temperature senders and see if you have any corrosion on them. Also check the wires at the connector for corrosion and proper security of the pins. Check to see if any pins or dirty, bent, or corroded. Pull on the wires at the connector as well (about 10 foot pounds of pull only). This is called a 10 pound pull test. If one comes out then repair the connector. Also, check your wire harness for rubbed through wires.
Vibration, heat, and saltwater make a good breeding grounds for wire problems.

Just do yourself a favor, take a deep breath when frustrated, and then continue with your troubleshooting. When it comes to wire issues it usually takes 10 times longer to troubleshoot than it does to fix the problem.

[jercat]

Reel Insane, thanks for your reply!! Yes you are right I am very frustrated but will follow your detailed recommendations this weekend and will definitely report back on my findings.
Thank you

[jercat]

Reel Insane, just to let you know hat I verified the thermo switches and they looked ok, connectors ok, 10lb. pull test ok and just pemding to perform the IR temp tester. I think I will also pull the thermo switches out and test the conductivity in hot water to see how they respond. I will report again. Thanks!

[Reel Insane]

Testing in hot water is a great idea. Everything may work fine when it is cold, but upon warm up they act up. I see that a lot with injector problems.

[jercat]

I removed the thermo swichtes, engine temp sensor and tested them in hot water. I recycle them several times to make sure they were ok and they are ok. I will keep using the boat and will look for a good Yamaha tech. The engine was running at 140F to 150F ( I push it up in neutral up to 4000RPM for a while). That is all I can do by myself. Thanks for the sugestions and help. I will report when I get to know from the tech.

[99yam40]

Did the temp switches operate as the specs say for them to open and close at certain temps, if so then I would be looking at wiring problems