225 Verado Overheating at Idle

[yolo]

Sunday coming back to my slip from a nice day of fishing (couple big fluke and keeper Sea Bass) the horn on my smart craft gauge went off indicating the motor was overheating, first time this has happened to me.

I did not have time to play with the boat much after getting back to the slip but I did do two things. I put the boat in throttle only and gave it throttle to about 2000 rpms, the temp immediately came down. I then shut the boat off, let it sit for a minute and started it back up, the boat heated up to 135 degrees at idle and did not heat up any further.

Yesterday I went down to the dock and played with it a bit more, and did the following:
A)Started the boat and let it warm up- The boat got to about 130-135 and did not heat any further.
B)Gave the boat throttle (in throttle only)- the temp fell to low 120’s I then brought back to idle and the motor heated back to 190. I gave it throttle to bring it back down. I did this two more times but I did not let the boat heat over 175.
C)I shut the motor off and restarted- the boat idled at 130 degrees and did not heat up further.
D)I gave the boat some throttle very quick and brought back to idle. The temperature began to rise again.


At this point I know something happens between idle from start – giving the boat throttle – and idle off throttle that makes it heat up. Then I started paying attention to the correlation between the water pressure and the water temp and noticed the following (all other system readings are ok);

A)I shut the boat down and restarted the motor- The boat sat at idle 550rpms with 1.0 to 1.1 water pressure and 132 degree temperature.
B)I put the boat in and out of gear with no additional throttle (forward and reverse)- the above numbers stayed the same.
C)Gave the motor throttle- I put the boat in neutral (throttle only), brought the RPMs up to about 2000 (water pressure raised accordingly and the temp fell to very low 120 ranges), dropped it back down to idle. Following this the water pressure dropped to 0.4psi and the motor began to heat up at the normal idle RPM of 550. I watched the temp and let the motor heat to about 175psi and then brought the temp back down by giving the motor throttle.
D)Once I brought temp down I shut the motor off and restarted- The pressure again read 1.0 to 1.1psi at 550rpm and the engine temp sat between 130 to 135.
E)I then gave the boat throttle only to 2000rpms and brought it back down to idle. At the normal 550rpms the water pressure dropped to 0.4psi and temp began rising. I then gave the boat throttle only again and brought to 600 to 650 rpms. The pressure went back to 1.0 to 1.1 and the temp dropped to normal.

From what I know (or at least think I know!  ) I either have a water pump or thermostat problem, it would not be the poppet valve because I’m not at a high enough RPM for the poppet to take over (correct me if I’m wrong on that). But I know I have low water pressure at idle (regardless of where it is at- 1.1 or 0.4), Mercury is telling me it should be at 2.0 to 2.2 at idle, it seems the temperature ranges are a bit drastic (when I was messing with it I was at 192 at one point and as low as 110), and it seems the idle temperature of 130-135 is low (Mercury says 142 to 149 is normal and below 130 is bad). And it makes sense that the horn went off Sunday because that is the longest that I have let the boat sit at idle while in gear. Generally when I’m in gear the boat is not at idle.

What I cannot figure out, and the reason I’m turning to you guys on this one, is I’m not understanding why the pressure and temp would keep when the boat is first started but fall off after the boat takes just a little bit of throttle?

Im also curious to hear opinions on the cause and solutions to the problem (tstat clogged, bad water pump, or somthing else). Thanks!

[yolo]

The impeller is about 200 hrs old so I was going to do it and the end of the season when the boat comes out of the water. The intakes are not clogged and I flushed the system, I also pulled as many hoses off the cooling system as I could to see if anything was built up or stuck in there. Also, I am in deep water all the time (the boat is in the slip and where I am I don’t hit shallow water). Unless something was floating in the water and got through the screen and lodged into the system, which was the first thing I checked, then its hard to believe something is in there. Also, I returned to the dock a few days later and the problem still persists so I know is something more that a temp clog or a plastic bag stuck over the screen.

Remember what I’m trying to determine is why the motor, at idle (not in gear and not throttled up), is losing the water pressure after it has been given throttle and brought back down to idle.

On all the sequences I performed, the boat was tied up at the dock, the motor did not go over 2000 rpms (Verados max rpm is 6,300) and was not held at higher rpm for more than five to ten seconds. To your other point, the boat is always at idle for a few minutes before I shut it off to ensure that supercharger has slowed and doesn’t keep spinning and brun up after it is shut off.

Keep in mind, as soon as the motor gets a small amount of throttle, 100 RPMs or so, then the pressure comes up and the motor cools down rapidly. Example I let the boat heat up to 190 degrees (this is where the alarm sounds). Once that happened I brought the RPMs to 2000 and the motor cooled back to the 120s within 10 seconds.

Remember the boat doesn’t need to move because I am having the problem at idle so the pressure from the moving water will not come into play, but Merc did give me some numbers on what the pressures should be around while running at different RPMs. I am going to run it tomorrow to see if these are low (if so I have a bad impeller). Also, I checked both the pressures and temps with Merc today on the phone to verify that the numbers in the manual were correct.

I get all the readings from the Smart Craft gauges, they throw a lot of info to you. I was thinking maybe the sensor was bad but I measured the temperature of the block where the sensor was and it was in line with the temp reading on the gauge. Also, there is a direct correlation with the drop in PSI and the rising temperature.

I’m going to change out the thermostats to see if that’s the problem, run the boat to check the pressures, and if the problem persists, haul it and change out the water pump.

[yolo]

Thanks for the post back Southern Cross.

You make some interesting points, that I never thought of before, about the water sitting down in the impeller and breaking down the rubber. The boat sits in the water with the motor tilted up at storage. After a day on the water I flush the system through the flush port with fresh water and that does have very good pressure. It defiantly makes sense that some could be sitting in there since it is tilted. The other thing you noted makes even more sense. I am constantly battling some people around me with smaller boats (15 to 18ft whaler and bow rider types) who are filling their boats at the slips with gas cans to save the minimal 35 cents a gallon on the water (these boats I’m talking about are not big enough for the slightly more expensive price of fuel on the water to make a difference). The problem is they are constantly spilling fuel in the water and it gathers around the boats mid tide in the static water. So if any of that water got in there it would make sense that it broke down that rubber impeller, and would do so rather quickly.

I know a bit about this stuff and motors in general but defiantly still need opinions and guidance to fully evaluate the problems. That’s exactly why I turn to you guys! If I didn’t post I never would have thought about water sitting in the impeller.

Also, I did read somewhere that a guy had a similar issue and it turned out being the power head. I am PRAYING that is not the case, but it seems like the guy i was reading on has a defective one from the manufacture. But, I was talking with the coast guard one time and he also noted that the powerheads go quickly on these motors if you get water in the exhaust. Again, PRAYING its not the powerhead.

I’m going to swap the thermostats tonight and see if that does anything, they need a changing anyway so well see if that makes a difference. If that doesn’t work I’m going to pull out of the water and swap out the whole water pump. I was going to do all of this when I pull the boat for the season because its due. Part that gets me is you have to change the gear lube and oil when you do this so I’m going to have to change the fluids now and then in two months when I winterize. Boaterslife!

Ill keep you updated and thanks again for sharing your experience!

[yolo]

LOL I always tell my freinds this when they ask me why i bought a boat:

"I went to the doctor for a check up, he told me i needed therapy.....so i went out and bought a boat!"

[Deleted]

Did you ever get solved that overheating issue? My 225 Verado started acting  same way. I have now changed impeller, thermostat and finally today poppit valve. Symptoms are equal. After intial starting temperature stays OK but after running on gear for a moment and slowing down to idle eg. trolling water temp begins to climb until horn. Getting revs up slows temp quickly.

Timo

[yolo]

I did! It ended up being the water pump. I just eneded up getting the whole kit and swapping everything out since i was having the problem. When I pulled it apart the housing looked worn and the oil seal defiantly needed a changing so i am glad I did everything. I also put a new thermostat in hoping it was that and the temps are running much better.

It sounds like you have almost exactly what was going on with mine.

Did you do the whole water pump or just the impeller?

[Simple Man]

Always change the housing with the impeller. Mercury taught me that by saying that they would void the warranty on a 225 ProMax if it wasn't done yearly. There was a reason that they were serious about it.

[yolo]

Agree with you Simple Man! I always do the full job.

But they do sell the repair kit for the impeller only and alot of people will have a shop rip apart the drive and only swap out the impeller, make no sense to me that a shop would not reccommend the full job. This is why i ask. I have also seen these things put back together without properly greasing things that are supposed to be which causes low water pressuers to persist.

scfa- also, do you have smartcraft guages? If so we can break down and pinpoint the problem a bit more. I was able to determine low water pressure being the problem becuase i have the digital water pressure readout on the guage. If we can start doing that we can figure out if it is water pressure or something else like the heat exchanger ect.