Are these F250's Running Too Hot?

[wahoo33417]

I have a pair of 2007 Yamaha F250's (3.3L) on a 282 with 300 hours each. Odd thing is the gauges for both engines show a constant engine temperature from idle on up to about 3800 rpm. No matter how long I run at 3800 rpm, the gauges stay put. Above 3800 rpm, both gauges take a small jump up and stay there for as long as I'm running above 3800 rpm.

If one gauge jumped up and the other did not, I'd be more convinced I have a problem. But both gauges behave the same.

I had the water pumps replaced as part of a full engine service 100 hours ago, when I bought the boat. Boat has run this way since I bought it. I did a chemical flush of full strength Barnacle Buster on both engines. No difference.

The boat gets better fuel economy at 3600 - 3800 rpm, so its not been hard to avoid the elevated temp. But that's not the best solution.

Any recommendations of a next step? Maybe others with these engines find that they run in a similar range on the gauges? But seems like it gets kinda high up in the gauge to me - assuming the gauge is accurate.

I'll paste some images below so you can see the how much the temp gauge jumps.

Tx, Rob

 

[WiltonGrady232]

I have the same engines and gauges. Mine do the same as yours. I've wondered the same, but have never had a problem.

 

[Doc Stressor]

My F250 would run one bar from the right side at anything over 4K. Since the gauges don't provide a real temperature output, we have to believe that is normal. My engine still made oil like crazy indicating that it wasn't getting hot enough to flash off the excess fuel from the oil. As long as the warning buzzer doesn't turn on and you don't throw an overheat code you will be fine.

 

[jtselios10]

My 06 282 with F250’s run at that notch on gauge too. I will know more this summer when I hook the motors to my nmea 2000 it will give me actual temp in degrees.

 

[wspitler]

Mine do the same for the past 900+ hours. I checked the actual temps via YDIS and they run at the design temps at higher RPM and slightly cooler at lower RPMs. Don't remember the actual thermostat design temps.

 

[magicalbill]

Remember when we had this convo after you got to Carrabelle? I told you my 2007 F200's did the same thing, just like the replies above. My tech said it was no prob; bells will go off if it really overheats as Doc stated. When I would come off plane an idle for a couple minutes, the indicator would slide back to it's normal reading until I got her above 3800-3900 again. Then it would jump back up 'till I slowed down.

I wondered about it, but ultimately dismissed it as there were no consequences associated with the "jump."

 

[wahoo33417]

Thanks guys. I remember, Magical. I just have too much 'imagination' when it comes to 12-year old engines with 200 hours on them when I bought them. But I now have 120 hours on them and they have been great. So at some point I should develop some confidence.

Tx, Rob

 

[seasick]

Just thinking out loud.

Since both motor exhibit the same condition and since it occurs after a specific engine speed I would suspect that the air/gas ration is changing or the cooling water flow has changed. In the later case, it could be the pressure relief valve has opened and that lowers the flow and pressure. Unless you have water temp gauges, you can't really tell.
In the former case, a leaner gas mixture will cause the motor to run hotter. The leaner condition could be programmed into the ECU, could be due to a weak pump or somewhat clogged filters or screens or could be injectors that just can't pass the volume of fuel needed at higher revs. If that were the cause, I wouldn't expect to see the same thing on both motors at the same time or more importantly on other owners boats.
Si, I am guessing it is pressure relief valve (poppet) related and is normal.

 

[seasick]

I forgot to mention that you can measure the head and t-stat housings with an IR, contactless thermometer to actually see the temps. I use one every season when 'un-wrapping' my boats and getting things in order for the boating season. The thermometer lets you measure not only temps but will also differences between head temps and whether additional investigation is needed.

 

[Doc Stressor]

As long as the water pump is working properly, the pressure relief (poppet) valve is wide open running at speeds much over 2000 rpm. If it is stuck shut on one bank you would definitely get an overheat warning buzzer. If it was stuck open, you would get overheating at idle speeds because the water jacket doesn't completely fill up at low rpm.

The temperature gauge monitor reading that the OP is seeing is normal.

 

[seasick]

As long as the water pump is working properly, the pressure relief (poppet) valve is wide open running at speeds much over 2000 rpm. If it is stuck shut on one bank you would definitely get an overheat warning buzzer. If it was stuck open, you would get overheating at idle speeds because the water jacket doesn't completely fill up at low rpm.

The temperature gauge monitor reading that the OP is seeing is normal.

Isn't there only one poppet valve on that motor? If so, I don't see how a bad valve would affect one bank bank only.
I do understand that a stuck open valve can result in low rev overheating but I don't see how a stuck closed valve causes an overheat warning. A stuck closed valve will result in high water pressure at high revs and would put excessive load on the pump.

 

[Fishtales]

I've seen an uptick like that from time to time and then it comes back. I'd say nothing to worry about and all the others here provide more ammo to do the same.

 

[HMBJack]

as Doc stated:
"As long as the warning buzzer doesn't turn on and you don't throw an overheat code you will be fine."

 

[Doc Stressor]

Isn't there only one poppet valve on that motor?

Of course, there is only one. And only a single thermostat as well. I don't know what engine I was picturing in my head.

The poppet valve needs to open at high rpm both to relieve water pressure and to facilitate the flow of water out of the cooling jacket. If the valve sticks shut the only way heated water can leave the block is through the relatively small thermostat opening and the pee hole. So the temperature goes up vs a properly functioning system.

 

[seasick]

I need to look at a water flow diagram to see where the poppet fits in the flow. My problem is that I have Yamaha and Mercury motors and the cooling technology is different. I have a lot more issues on my Mercs and few on my SX motor so I tend to approach many of the questions on this board using my Merc mentality.
BTW. I think that motor has two t-stats

 

[Doc Stressor]

Only 1 t-stat on the 3.3 F250. This time I checked in the service manual.

My current Honda BF250D has 2 t-stats and 2 pressure relief valves. Each cylinder bank is cooled separately. That's why I was confused. When you get old, it's easy to confuse the past with the present.

Here is a diagram of the water flow pattern for the Yamaha F200-250. You can see that both the thermostat and the relief valve control water leaving the engine. The t-stat is on the top of the block and the poppet valve is at the bottom.

 

[wahoo33417]

Thanks guys. The education to be gotten from this forum is worth the price of admission. It is valuable to the many of us that knowledgeable folks are willing to share.

I'm convinced it is just the way these engines run - or at least the way it is shown on the gauge.

For what it is worth, the thermostats were replaced to no effect. I will have to check on the poppet valves.