2004 Optimax 225 cold operating temperature

[apenland01]

I got my new vessel view mobile installed this weekend and took it out on Sunday. My temperature gauge was broken, so I have never known what my engine temp is until now, which is why I bought the vessel view mobile. I've owned the boat since August and previously just idled through a long no-wake zone and then fast idled a bit more to make sure it was up to temp before taking off. I always let it run for about a minute or two after getting in place to let the temps stabilize.

Anyway, after idling through the no-wake zone on Sunday, the engine never got above 108. I went to about 1500 rpm for a few minutes longer and it never got above 111. Since it had been running for about 15 minutes already, I went ahead and got on plane, then kept it about 3500rpm for about 5 minutes. The temps were around 102-105 the entire time. Once I got in place and idled, the temps never rose above 111. Water temp was 54 degrees and outside temp was about 58. Is this normal operating temperature in 54 degree water? Is the vessel view mobile reading taken at a point that would show a lower temp than usual? I've always had the idea that I shouldn't run the Optimax hard until it hits 120 or a little hotter.

Since this is a 2004 Optimax with about 70 hours on it, I'm a bit paranoid about cold seizing this engine.

[Savage]

Check both thermostats for debris. Never try to get on plane until the motor reaches 120+ degrees. You dodged a big bullet!

[apenland01]

Thank you! I have been driving it like this since I bought it last year. It's possible it has never been up to operating temperature, since I didn't have a temp gauge this whole time.....

[06 SB]

A perfect example of why you cannot just let it idle for a while. There are those that think spending money on a Smartcraft gauge is money wasted. It is WELL worth the $ in my opinion.

[OH_Ranger]

If you have an infrared temp gun, you could probably isolate which one is stuck.

[10ga]

Not trying to highjack your thread but other than this issue, how do you like the 225? I'm going to look at a 2004 TR-20 Triton tomorrow with the same engine. He said in the spring when the water comes up and gets full of trash and limbs, his does the same thing. He said he took it to the mechanic and he said there was debris in the thermostat and it was stuck. He said the guy showed him what to do and after the thermostat was clear, it was fine. Said he wound up doing once a year.

[apenland01]

I love this engine, it's been fantastic so far. It has fired up every time in less than a few turns of the motor and runs flawlessly. The sensor in the engine mounted oil tank had gone bad and alarmed the first time I had it out. Most likely because it hadn't been used much in the recent past. Once I got that replaced, it's been great. If the engine has good compression and checks out on the computer, I wouldn't hesitate to buy another one. 2004 and newer had fewer problems than the earlier models.

[tomloans]

Your temperature will decrease at top end speeds and also at hi idle as you are motoring out. On plane at lower speeds where you may be somewhat barely on plane, then your temp could stay at 120ish. 120ish only happens only when you are at perfect idle and neutral. Mercury states that you should Idle for 10 minutes before you hit it. If you give it gas it immediately starts going down. Mine usually will reach 122 at idle but the minute I put it in gear and start idling faster like in a 5 mile an hour zone, the temp will go down. After idling through a 5 mile zone I will look at the temp and will actually put it in neutral and wait a few seconds for it to come up a bit before I hit it - if the temperature dropped below 105 to 110. Overkill probably but that's what I do. Mercury states that you should Idle for 10 minutes before you hit it. So I am not sure if 120 is the magic number but the motor needs to warm up for sure and around 110 to 115 is not the end of the world as least with my talks with the Mercury guys.

IN your case though, there might be something stuck in one of your thermostats. Pull them both out and clean them. I usually also flush the motor ( not running ) so water pours out of two areas for a few seconds. Once you do this, go fish and enjoy the boat.

One time I couldn't get it above 100 degrees at idle and I had a piece of wood the diameter of a toothpick and about 1/4" long stuck in a thermostat, so pull the thermostats for good measure. And no you didn't hurt your engine.

[angle iron]

Your temperature will decrease at top end speeds and also at hi idle as you are motoring out. On plane at lower speeds where you may be somewhat barely on plane, then your temp could stay at 120ish. 120ish only happens only when you are at perfect idle and neutral. Mercury states that you should Idle for 10 minutes before you hit it. If you give it gas it immediately starts going down. Mine usually will reach 122 at idle but the minute I put it in gear and start idling faster like in a 5 mile an hour zone, the temp will go down. After idling through a 5 mile zone I will look at the temp and will actually put it in neutral and wait a few seconds for it to come up a bit before I hit it - if the temperature dropped below 105 to 110. Overkill probably but that's what I do. Mercury states that you should Idle for 10 minutes before you hit it. So I am not sure if 120 is the magic number but the motor needs to warm up for sure and around 110 to 115 is not the end of the world as least with my talks with the Mercury guys.

IN your case though, there might be something stuck in one of your thermostats. Pull them both out and clean them. I usually also flush the motor ( not running ) so water pours out of two areas for a few seconds. Once you do this, go fish and enjoy the boat.

One time I couldn't get it above 100 degrees at idle and I had a piece of wood the diameter of a toothpick and about 1/4" long stuck in a thermostat, so pull the thermostats for good measure. And no you didn't hurt your engine.

My temp never drops till I get on plane.

[SilverFox579]

My temp never drops till I get on plane.

+1.

No way I'd accelerate until I see minimum of 120° just like Don has repeatedly posted here.

[EuropeanAM]

In addition to inspecting/testing the Thermostats- you need to make sure that you actually HAVE 130 degree thermostat in the engine. If not- get with Rhonda and she can assist with the correct kit.

[apenland01]

Thanks everyone. I've got the boat scheduled for the shop next week to get the thermostats replaced with the 130 degree versions. I'm not sure what is in it now, but I'm not willing to take a chance on these and I'm willing to spend a couple hundred bucks to have new thermostats installed instead of taking a chance of ruining a great engine with only 70 hours on it.

[apenland01]

I'm looping back to update this thread. I got the new thermostats installed and the mechanic said he thought the thermostats looked good, no debris and they were the original 130 degree stats. He put the new ones in and I took it out on Saturday for a test run. The vessel view mobile now showed temp was at 120 or more within a minute or so. By the time I got out of the no-wake zone, it was bouncing between 122-128 and I was able to clear the no-wake zone and get on plane.

So even though the original 15 year old thermostats looked good, obviously, one or both of them was failing, since the motor came up to temp quickly and ran great all day after the new stats were put in. I wasn't sure if I was just throwing money away, but replacing the thermostats was a great move and likely saved my engine.

[Savage]

Perfect.

[SilverFox579]

+1!