2015 Motor MerCruiser 4.5L 250hp NO EC - OVERHEATING!

[Lou C]

Thanks to All Dodge for info on how these newer systems work and glad you’re getting better results. Hope the water test goes well.
BTW the deposits you see in an engine that’s been run in the salt are actually calcium more so than salt which dissolves easily in water. This is what I saw in my old cyl heads when I replaced them in 2017. While you could see calcium deposits it wasn’t much & not enough to restrict the cooling passages.
Running the deposit removing solutions is probably a good idea with raw water cooled engines in salt. Even so I haven’t done this & any overheating issues I’ve had were due to other causes….marine growth in the lower unit, clogging in the manifolds, etc. Even with the old original block from 1988 it runs at a cool 160* except when coming off plane when it may rise to about 170-175 briefly.
My brother’s boat (2020 Chaparral) with the 4.5 200 hp runs at a cool 140 all the time…

 

[Lou C]

Just to show how different systems are from one another, on my old OMC/Volvo style cooling system here are the normal temps:
engine warmed up at idle speed:
with dash gauge reading 160* and a 160* thermostat....
top of thermostat housing, 135*, intake manifold right under where the stat housing bolts on, 145*
big hose from the stat housing to circulation pump, 135*
manifolds and elbows 95-110*

after coming off plane, main difference is that the temp gauge will rise to 170-175 temporarily and the max temp of the elbows & manifolds is approx 135*
I think Merc had to redesign the exhaust to keep the manifolds hot enough to make the cat converters work as designed
They also used to have a warm manifolds system (pre-cat converters) where the manifolds didn't get water flow till the thermostat opened up, this was to avoid condensation in the exhaust system which can occur in 'cold manifold' systems where the manifolds are continuously fed incoming water. On the "warm manifolds" systems the manifolds ran at about the same temp as the engine or slightly hotter. The temp below which condensation can occur is about 120*. While I don't know this for sure I think this is why OMC and Volvo used 160* stats instead of 140* stats, I tried a 140 because I heard that's better for avoiding deposit build up but then I had condensation in the exhaust, so I went back to the 160 I have used for years. The deposit build up issue at least where I am in Long Island NY is not a significant issue.

 

[leosmdp]

Yes! I saw that valve alldodge (what is more i have in my favorites but for this alpha model is not working )
For that one who want the valve..

https://www.amazon.com/gp/product/B005Q5M3UO/ref=ox_sc_saved_image_1?smid=ATVPDKIKX0DER&psc=1

 

[leosmdp]

LouC yes your motor is running in another temperature at all..
your brother's boat is similar to mine if is the alpha 4.5 version, if it the bravo instead this motor has a heat exchanger.
hope on water test got some good results.. I keep you posted.

 

[alldodge]

Yes! I saw that valve alldodge (what is more i have in my favorites but for this alpha model is not working )
For that one who want the valve..

https://www.amazon.com/gp/product/B005Q5M3UO/ref=ox_sc_saved_image_1?smid=ATVPDKIKX0DER&psc=1

Alpha has more issues, if you use the same valve it will shut off the flow from the drive when motor is running. I don't know if there will be damage doing that to the pump but there might be.

Might need to add another Y connection so drive can pump salt water over the side when motor is taking in fresh

 

[leosmdp]

Alpha has more issues, if you use the same valve it will shut off the flow from the drive when motor is running. I don't know if there will be damage doing that to the pump but there might be.

Might need to add another Y connection so drive can pump salt water over the side when motor is taking in fresh

Yes Sir alpha is the first version.. and is what I got right now.
About the valve I can’t use because if I put it at the bottom water entrance hose of the motor the raw impeller in the alpha steam drive I guess is going to burn out . That why I chose in my inexperience the dual flush rubber to flush and it’s works

 

[Lou C]

BTW I had trouble with some of those dual inlet muffs because the rubber was too stiff to seal well against the lower unit. I had much better luck with the Mercury/Quicksilver round muffs with the metal clamp.

 

[leosmdp]

LouC, yes I guess depending the brand you bought it. I started with one that I personally didn't like and then I purchased another that works much better and looks more solid as well.

So today I made two tests before hit the water tomorrow if I could.

1st I put again only one original black hose that's goes to the thermostat from the hose assembly (M TO I) S-Shaped.- and SURPRISE AGAIN the temperature got higher again until 170 when I stop the motor and change again to)
the 2do. test I put again the clear kinked hose and pum! the temperature went down and stays at 150 again.
Strange situation tomorrow I will check it..
(Note: All the black original hose I cleaned brushed and put a rust remover to the rubber to remove everything and there is not more metals sediments glued to the sides walls. water flows ok that's why Is strange).

 

[alldodge]

1st I put again only one original black hose that's goes to the thermostat from the hose assembly (M TO I) S-Shaped.- and SURPRISE AGAIN the temperature got higher again until 170 when I stop the motor and change again to)
the 2do. test I put again the clear kinked hose and pum! the temperature went down and stays at 150 again.

With a kinked hose it stays cooler then when its not kinked

Is the thermostat in stalled in crossover?

Check the vanes on the circulating water pump. With hose removed use a long thin screwdrive and put up inside. See if it will make contact with the vanes and see if you can keep the pump from turning. I'm wondering if the vanes may have broken away from the shaft

 

[leosmdp]

yes, I put a new thermostat in the crossover.
circulation water pump ( 8m0116534 ... 370$) is the only thing I did not change when disarmed and but I checked if move smoothly and it did, I tried to check the vanes with a screwdriver and I couldn't .. anyways the last thing.. I will disarm the hoses and put an inspection camera on it or a zip to check if there are vanes or not.
attached is the only photo I took from inside but could see nothing.

 

[leosmdp]

Guys yesterday I took out the circulation water pump from the motor to see better inside .
I tried cuz was so hard saw inside and yes inside are all the vanes (posted a YouTube video to show to you)

At idle with garden hose and a bucket full of water the temp stays at 155 and the kinked clear hose.
Today a making a water test ..I’m here right now and temp went high again. I was any ways running at 180 when suddenly temp went down fast (after open the motor housing I noted that One hose that’s goes to the water pump took off and water went out everywhere. Waiting to put the original again…
I’m really frustrated i don’t if I need to change the poppet valve? (I already disarmed and put new diaphragm) water pump any ways? Or head gasket !
Ufffff…
If you know a good mechanic or someone here around north Miami fortlaudade dania in Florida again .. I’m at that point right now

 

[alldodge]

Don't know of a mechanic to recommend in FL

Without hands on, it might be in the crossover. Reason to mention that is motor stays cool when a kinked hose is installed. As before the only reason I can see for the m to i hose is for draining during winterization. There should be no water flowing down when motor is running, yet it does if hose is not kinked

Might have a clogged up bypass port inside the crossover

 

[leosmdp]

I didn’t disarm the crossover yet but sure I will do and will clean as I did with every single part I took out from this motor. thanks again alldodge for your support always

 

[alldodge]

Wait a minute, that doesn't look like the right part. Is it that same as the other motor and does it have the thermostat in it?

 

[leosmdp]

No no alldodge that photo is actually the circulation water pump yesterday before put again.
Right now I put again the original black hose from assembly to the water pump and noticed air bubbles from assembly to the thermostat in the kinked hose.

Temp at idle went to 180 here at salt water.
Ommmmmm!!

 

[alldodge]

ok, thanks

Here is what we know, and correct if I'm in error

With clear kinked hose in place the motor stays cool
With non-kinkied hose it over heats

The crossover is part intake and part thermostat housing (TH).

Prior to a crossover water moves from the raw water pump to TH and passes with low restriction to circulating water pump and exhaust. When Tstat opens hot water flows thru and in other side of TH and out to the exhaust

Our pics showing water flow is not correct in all areas. The water should flow up from I to M, under the Thermostat and then out the exhaust to keep exhaust cool. It's flowing the other direction or not at all.

The water going to the exhaust mans should come from poppet valve and from TH. There should be enough of a restriction between mans and exhaust elbows so mans stay full and only excess goes from mans thru to elbows.

There is either to much restriction between mans and elbows, or poppet valves are stuck full open. My guess due to water continues to run down from TH to Y (M to I) the mans are clogged

 

[leosmdp]

Alldodge yes you right for me too. something is clogged here there or maybe head gasket burned as louC suggest but I don’t know what!
My first shot was manifold and riser I tried really hard to clean with acids brushes all the debris rust from the conductors cuz the parts were solid not weak . I tested manifolds and riser with the garden hose in every single hole and the flow went out without issues but yes maybe they are the originals and reduced the flow somewhere, but u didn’t notice the where clogged on my tests before put it back. I didn’t notice any block when I insert water in one conductor the water went out in the other side
In this motor model manifold riser kit cost around 2600$… the key is if that solve the problem it’s ok! but if not..

Tomorrow I will have some time to work on the motor I will disarm the crossover and maybe put some rust off to the inside motor there is some liquid to recommend perhaps ?
I always do a flush with salt remover but this product is weak and just for maintain

Thanks for your time answering me you are like a light in the path. Where ever you come down to south Florida I own you a couple beers.

 

[alldodge]

Will water go in the bottom of the man and come out the exhaust?
If it does then it may be in the crossover or the poppet valve

 

[leosmdp]

What do you mean from the bottom? the check valves? I couldn't took out the check valves (was glued I guess) but when I insert water in the main holes (where water goes and come to cool the exhaust) a thin flow of water comes out of the check valve. I calculate because the inner ball was exerting pressure. (I brushed it off anyway and tried to clean it up) Today I'm going to take the crossover apart. It's your turn I hope that's it.
if you mean Bottom to the conducts in the same manifolds yes went out and flows without issues.
if you mean from inside the exhaust conducts, no. They were solid, without leaks, I checked them with the interior camera. That's why I took the work to clean them thoroughly.

 

[leosmdp]

Don't know of a mechanic to recommend in FL

Without hands on, it might be in the crossover. Reason to mention that is motor stays cool when a kinked hose is installed. As before the only reason I can see for the m to i hose is for draining during winterization. There should be no water flowing down when motor is running, yet it does if hose is not kinked

Might have a clogged up bypass port inside the crossover

reading everything again, yes from the crossover when the motor is on, a thin flow of water move from the crossover to the check valves.