Mercury OptiMax cooling system alarm

Mercury OptiMax outboards must run at the normal operating temperature (120F + at idle)or you may get an alarm and/or a poor running engine. Something to look at if you are getting a cooling system alarm and/or all of the spark plugs are fouling out on one bank of cylinders. Thanks for watching!

[@csalinas-sf6jg]

Thanks for the video sir. I was actually looking to find how the water circulation

[@sloth-worx]

Glad this video was helpful. Thank you for watching and commenting!!!

[@Sunrisenails1925]

I have a question I have 225 HP optimal. Run idle is fine but when I accelerated it turn off. I clean fuel tank and try to run small tank doing the same. Thx ☺️

[@franciscallahan4213]

Did this sound 6 beeps? I'm trying to diagnose my motor as well

[@matthewsharple]

i have a question.... I have a 2006 opt 225xl .. theres no water circulation. I have ordered the water pump and thermostats to see if that fixes it but shouldnt i be able to run the motor with the flush out valve on the lower cowl? I did that and the temp kept climbing... what would you suspect? what would i check next after the thermostats and pump is replaced?

[@sloth-worx]

If you are looking at the back of the engine on the left hand side (port side) below the power head is a strainer screwed into the adapter plate. You will need to remove the lower cowl to get to it. There will be a rubber hose attached to it that goes to the compressor. Pull that hose off, unscrew the strainer, pull it out and clean it. That strainer supplies the compressor with cooling water if it is plugged the compressor will overheat and sound the alarm. That same water line ends up at the pisser, so if your engine isn’t pissing there could be something wrong with that little cooling loop. Not knowing the history of the engine, that’s where I’d start. Also get a cheap temp gun check both heads and compressor to make sure you actually have an overheating problem. I’ve come across a few bad temp senders. Good luck. Thanks for watching!!!

[@TX_Nupe]

Without looking at the readout, was the engine acting weird or showing strange signs?

[@sloth-worx]

Warning horn would sound once and the smart craft gauge would say something like thermostat cooling system. If left alone long enough you may get a running rough and one bank of spark plugs fouled out. Hope this helps Thanks for watching!!!

[@RechnersAdventures]

I’ve got a question for you. I’m having similar issues on a 2011 optimax 250. I’ve replaced both thermostats and it still won’t reach operating temps at idle. Lucky to see just over 100 degrees every now and then it will get a little warmer but will not hold above 100 at idle typically. Not sure what to go after next have a new poppet valve was going to try didn’t know if you had any ideas.

[@sloth-worx]

Have you verified with a temp gun that the engine is running the same temperature as the gauge is reading? I have had issues with the temp senders reading wrong on occasion. Other than that it is Definitely worth looking at the poppet valve. It isn’t very hard to access with the lower cowling removed. It is possible that it could be wedged open slightly or the grommet could be damaged. Hope this helps. Thanks for watching!!!

[@RechnersAdventures]

I put a new poppet valve on that didn’t help. I have not verified with a temp gun but based on feeling the head both lower cylinders seem to be a lot cooler to the touch. I’ll have to get a temp gun and check it out.

[@cobrayzf]

Did you use aftermarket thermostats? I had a similar issue. One of mine was bad and I had purchased 2 after market OMP thermostats. I found that they were not closing properly letting just enough water through that it could not get to operating temp. Put 2 new mercury ones in and problem was solved.

[@josemariatrueba4568]

Poppet valve must be closed in order to get high enough water pressure to reach the thermostats. A partially opened relief valve will avoid water reaching the upper part of the engine where thermostats are located. Poppet valve should start opening above 1500 rpm when water pressure is high enough, otherwise hot water can't exit the engine resulting in very poor water flow causing high temperatures that may trigger the temperature alarm and eventually destroy the engine. An opened poppet valve at very low rpm may cause the engine to over heat because water pressure is too low. Conclusion is that when everything goes right, thermostats control temperature by opening more or less below 1500 rpm and poppet valve controls temperature moving freely above 1500 rpm. A clogged poppet valve, which is a common problem, results in proper cooling al low rpm but very poor cooling above 1500rpm.

[@zellerized]

Ok so i have a 40hp merc and this season i changed the water pump as it wasnt peeing after sitting over winter.. i then took it out and it ran hard across the entire lake but when slowing to idle speed, 2mph, it gives the overheat long alarm.. just replaced the old thermostate and gaskets.. havent gotten to popit valve yet. Thoughts?

[@csalinas-sf6jg]

Subscribed!

[@sloth-worx]

Thanks so much!!! People that take the time to subscribe is definitely what keeps me motivated to do more. Thanks again, it really means a lot!

[@randy1ization]

what computer are you using to access the data on the motor? is there a bluetooth device?

[@sloth-worx]

I’m using mercury’s g3 software. I think it’s only available to dealers. There is the option of the Bluetooth vessel view but I haven’t used one and don’t really know what information you can access with that device. Thanks for watching!!!

[@jamesmccaskill7329]

Question what alarm code did it give. Having a 6 beep alarm on first take off and no fault code in computer.

[@sloth-worx]

One beep periodically, smartcraft gauge said something like warning cooling system. Wouldn’t do it every time we took it out. The 6 beep alarm is a tough one, you’re probably not wanting this answer but you will probably need to run it by a dealer and get a print out of the (freeze frame data) this will or should log the issue causing the alarm. Unfortunately some faults won’t stay stored in smartcraft or vessel view. Hope this helps. Thanks for watching!!!

[@jamesmccaskill7329]

@@sloth-worx Thanks for the reply. I was just curious as if anyone might know. Just got the boat out of the shop today and made a test run. I've always had older boats and motors. They were easy to troubleshoot and even fix. The 6 beeps alarm according to the dealership was a bad thermostat. I would normally change that myself I decided to let them do the work. That won't happen again. It appears that the 6 beep alarm could be a lot of things and you're right about not showing up on my vessel view and even when the tech connect to the computer it didn't show a code. I have had the motor sound one long continuous beep from running hot due to grass around the intake. But to have that 6 beeps then I would shut down and restart and run with no issues had me puzzled. Never the less she's back to running hopefully for a long time like my old 95 Johnson fast strike. That motor was bullet proof.

[@thebasswicker6294]

What’s the part number for the stat

[@sloth-worx]

T-stat is 8M0057307 should be the same for 200 225 250 opti. Gasket part # 27-850318

[@thebasswicker6294]

@@sloth-worx thank you Sir