Mercury optimax running hot?

[Hamonrye]

Hi I have a 2007 Mercury optimax 150, SN 1B459138. Under light acceleration 1200-1500rpm I notice the temp will sometimes creep up to the 160-170degree range at which time I put in neutral and it will drop down to around 140-148degrees. On plane I have no issues, pressure is around 10-12psi and temp around 98-100degrees. Is this normal? I feel that it’s on the high side. Water pump is new, pee stream is strong, and all temp readings are coming from the smart craft gauge. To my knowledge the t stats have never been replace but correct me if I’m wrong those only come into play at idle from what I’ve researched.

[JOE54]

off idle plowing will result in higher temps for sure , would replace stats , engine is not designed to for that type of operation too little water flow for the load

[Savage]

Wrong forums Sir. Your 150HP motor is not a 3.0 liter. Try the boards above this one.

[Hamonrye]

Gosh dang it , that’s what I get for using my phone to post . Thank you. Moderator please delete

[EuropeanAM]

How about I just move it for you.

The gasket underneath the impeller plate is likely torn or split.

[Hamonrye]

I just removed the lower unit to inspect the water pump. No issues found, all the gaskets are intact. I happen to have another WP kit on hand and threw it in anyways but I don’t think that will fix the problem. Any other ideas? I plan to order some thermostats from Rhonda just for the the heck of it since I don’t believe they have ever been changed. And one quick thing to note as someone mentioned it, I did notice that when light accelerating and not “crashing” into waves the temp is lower, around the 150degree range. It’s only when I’m light accelerating into waves where the temp creeps up. And in case anyone is wondering why I drive like this sometimes is that my particular boat is fairly small and tears up my back when on plane and there’s a decent amount of chop on the water.

[EuropeanAM]

Please tell me you replaced ALL THREE (3) gaskets in the kit?

If so, I'd recommend you launch and see how it does. I've seen the gasket problem overlooked repeatedly by techs with decades of experience.

[Hamonrye]

Yes sir I followed the water pump write up by solverfoxx that is pinned in the FAQ forum. All 3 gaskets have been replaced. I will take it out in the next week or so to see if there is any difference and report back. Thank you so much!

[EuropeanAM]

In the meantime- see if you can snap a picture of the components you removed. Be interesting to see.

[SilverFox579]

Yes sir I followed the water pump write up by solverfoxx that is pinned in the FAQ forum. All 3 gaskets have been replaced. I will take it out in the next week or so to see if there is any difference and report back. Thank you so much!

If you followed it to the letter the water pump should be fine.

[aussiejake]

Had the same problem recently, found seaweed wrapped around the poppet valve spring, restricted the opening at off idle lower rpm but must have opened enough once on the plane at 3000 rpm + to lower temps.

[Hamonrye]

Sorry for the delay, some unfortunate bad luck. My truck was parked outside and totaled by an uninsured drunk driver. Needless to say I have not been able to take the boat out. I was able to find the old gaskets. And this time around I changed the base as well.

[Hamonrye]

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[Hamonrye]

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[EuropeanAM]

[Hamonrye]

I’m finally back with an update. I replaced the water pump and both thermostats. ordered parts through Rhonda so I know they are correct and genuine parts (= I was able to take the boat out and run it around with the same issue. Runs a little warm at slight throttle. Seems like it runs a little warmer if anything but could just be the lake temps being higher. Going to try the poppet valve next. Quick question, when I replaced the water pump the copper water pipe came out with the lower unit which has never happened. I re installed it into the motor and it felt okay (not loose) and then installed the lower unit as usual. Could that upper water pipe seal be the problem? And should I go back in there and replace it?

[JOE54]

dout its problem , you know powerhead has to come off to replace that, along with both plates underneath it

[Hamonrye]

I checked the water strainer and it was clear of debris. My next shot in the dark is the poppet valve. Upon inspection it appears to be in good condition. Am going to replace it anyways. Do you guys recommend replacing the seal that goes into the block at the back of the poppet valve? Visually looks to be in good condition and the rubber still feels soft.

[SilverFox579]

What is your at idle temperature and water pressure?

[RickCamilleri]

Under load the poppet takes over so id be inclined to think it's that, esp seeing how your compressor strainer was clear of debris