Hi everyone. I'm up north. Overheat alarm on my optimax 225 has been going off. Smartcraft is showing temps going up to 183. I do have water coming out of the tell hole. Took off the lower unit. Impeller looks ok... although I'm not sure I would know if it was bad. I've never replaced it yet....100 hrs and 4 seasons plus this season. Thoughts or ideas would be much appreciated! Thanks! Markbano
Try a new impeller. That will probably fix it. It should be replaced every 2 years in my opinion. jim
Thanks Jim. Willdo. I will bring it up next weekend. I read something about sticking poppets being a potential problem.. not sure what and where those are....
The poppet valve controls water pressure. Check the idle and 3000 rpm water pressure before and after the impeller change. Post the results. I would guess that the pump output is down and the poppet is closing down some to maintain pressure and the the flow is down as a result causing the overheat. The high temp is hard on the electronics, so don't delay the pump change. jim
Mark, It is good to hear that you had time to use your Dyne. My 200 had some leaks around the heads and exhaust cover. But to our surprise, the poppets on one bank were missing in action allowing that side to run cold and the side with poppets to run hot as the water would seek the path of least resistance. Think back to whether or not your Dyne has been run in shallow areas where it may have picked up some foreign material (detritus, sand, aquatic vegetation, schools of muskies, wayward diving bells) that may be blocking the intake screens and possibly lodged further up the cooling circuit. Did you try the flushing port with a high flow garden hose? Worst case scenario, could there be Zebra Mussels or the like haunting the cooling jacket galleries? As the esteemed forum member Jim stated, replace the pump with the OEM kit per service manual instructions and see if the condition abates. Carry On, Counselor. Tim
Tim, Your situation is why you should run temp probes in both banks. Probes and gauges are cheap. Overhauls are $$$. jim
Thanks Mr. Jim, I will begin the process asap. My 1977 Evinrude 200 has an overheat alarm, but I am unaware if it has circuitry for temp gauges. There are probably ready made solutions for this motor that I have not found. Tim
My motor has machined holes in the heads that do not go through to the water jacket. They accept standard sensors. You may have unused wires in your harness, or you might have to run wires. They gauges generally come with matched sensors. jim
I bought new spark plugs (wow, are they ever expensive $$$). I also bought a new impeller. I will fly up tomorrow and install everything. While I'm at it - how do I backwash the cooling system/screens? I see that there is a screw port on the back of the engine with a plug in it. Do I put a garden hose in there? Where are the screens and how do I access them? We do have a very weedy lake so maybe they are plugged. Meanwhile - my boat guy here in Illinois tells me that the warm air and warm lake temps in the midwest are causing a lot of overheat alarms on Optimax engines with weak impellers, so his suggestion was that I replace it. My temps are not that far above normal so I hope this does it... I confess that I didn't pay any attention to the water pressure reading. The temp, however, was going into the upper 170s and even up to 183 a couple times. Not sure what temp it is supposed to operate at...
Mark, To flush the powerhead, remove the plug from the fitting in the bottom of the cowl. Attach a garden hose and flush with clean water. (Don't exceed 45 lbs. of water pressure.) The only way I know of to flush clean the cooling system in the (lower unit) is with the cuffs and engine at idle in neutral. Bob
