Mercruiser 6.2L Coolant Loss

[PremierPOWER]

2018 Mercruiser 6.2L engine. Coming back from our tie up the other day, my port engine lost all coolant. Checked the oil and it is good. I'm guessing it has to be a coolant hose somewhere, the splatter seems to be inline with the belt. My plan is to fill it back up with coolant, start it up, and see where the leak is coming from.

I also need to check the raw water pump impeller. My only guess is that it failed, causing the coolant to overheat and burst out a hose somewhere. Any other thoughts or suggestions?

** Ignore the small gas can, that is not gas. I use it for generator oil changes while away from the dock.

 

[alldodge]

Single point drain piece of crud most likely.

 

[PremierPOWER]

Single point drain piece of crud most likely.
View attachment 370535

Ill take a look there, thanks!

Also, as noted in my post, the gas can is not gas. I use it for generator oil changes when I'm away from the dock. Old oil only in there.

 

[alldodge]

Your right my bad, and it can't be the housing, that is raw water only not on the HE side. If its not something like a plastic block drain fell out due to not being tightened enough or cracked, then just puts some water in the HE and see where it runs out

 

[Lou C]

the engine with the leak seems to have a residue of something near the hose connection for the exhaust manifold on right hand side in the pic....maybe a clue?

 

[tpenfield]

Those engines look very familiar to me. (I have their 350 HP cousins )

Anyway. Assuming that you have VesselView (?) Were you getting an overheat warning/alarm? If you think the impeller failed, were you seeing the proper amount of pressure for the raw water side?

Did the coolant blow at the end of your trip, or did you run for a while without coolant?

Most of the closed cooling hoses are in the front of the engine and connect to the crossover assembly. Most of the other stuff is on the raw water side, including the drain housing that @alldodge mentioned.

 

[PremierPOWER]

Those engines look very familiar to me. (I have their 350 HP cousins )

Anyway. Assuming that you have VesselView (?) Were you getting an overheat warning/alarm? If you think the impeller failed, were you seeing the proper amount of pressure for the raw water side?

Did the coolant blow at the end of your trip, or did you run for a while without coolant?

Most of the closed cooling hoses are in the front of the engine and connect to the crossover assembly. Most of the other stuff is on the raw water side, including the drain housing that @alldodge mentioned.

It started alarming on my VV502, the problem is I am having connection issues and cant see anything on the Vessel View at the moment. I was idling out of the cove and figured it was a low gear lube alarm (Just changed it recently and meant to top it off, so this was in my head). I checked real quick and it was a bit low but fine so I tried to plane out and it went into limp mode. At that point, I saw steam coming out and shut down. At first I thought my Halon system discharged, but it was just the coolant blowing on the hot manifolds and steaming. Engine didn't run long at all without coolant.

Sunday morning I was too hung over to pull the impeller out to check it before leaving the lake, so that is just my assumption. I'm going to go back tomorrow and start digging into it. Might just use some distilled water instead of coolant to find the leak, then drain it, fix the leak, and fill with coolant.

 

[tpenfield]

How did you get so hung over? Bad ice in the drinks?

You can probably just look around the front of the engine for a broken or loose hose. If that fails, then do the heat exchanger fill. The water will probably be noticeable even without running the engines. Make sure not to leave plain water in the cooling system, if you are getting towards colder temperatures.

Probably need to fix the VV display as well, since it is your view to the engine info (temperatures, pressures, warnings, etc)

 

[PremierPOWER]

How did you get so hung over? Bad ice in the drinks?

You can probably just look around the front of the engine for a broken or loose hose. If that fails, then do the heat exchanger fill. The water will probably be noticeable even without running the engines. Make sure not to leave plain water in the cooling system, if you are getting towards colder temperatures.

Probably need to fix the VV display as well, since it is your view to the engine info (temperatures, pressures, warnings, etc)

Trust me, I have been trying to fix the VV issue. It is a loose connection somewhere, because I have two VV502's and they both do the same thing and it is intermittent. Every once in a great while, they will display the data. For the life of me, I haven't been able to track the loose connection down.

 

[tank1949]

Your right my bad, and it can't be the housing, that is raw water only not on the HE side. If its not something like a plastic block drain fell out due to not being tightened enough or cracked, then just puts some water in the HE and see where it runs out

I don't know why MC uses plastic anywhere in the cooling system. I replaced plastic plugs on my CC exhausted manifolds with brass and/or galvanized. I will sleep better.

 

[PremierPOWER]

Well, that was an easy find/ fix. Turns out, I could have probably tackled this on hungover on Sunday lol.

Stupid blue plug broke off. Hardest part was getting the old one out. Ended up heating a screw driver up with my heat gun, jammed it in, let it melt the plastic onto the screw driver, and it came right out.

Ended up putting about 7 quarts of coolant in, so it hadn't lost all of it (holds 17.9 quarts). Ran it for about 20 minutes and all seems good.

 

[alldodge]

Good deal
Could replace the plugs with stainless Hardin Marine, but already refilled
https://www.hardin-marine.com/p-810...mercruiser-22-806608a02-8m2000874-5-pack.aspx

 

[PremierPOWER]

Good deal
Could replace the plugs with stainless Hardin Marine, but already refilled
https://www.hardin-marine.com/p-810...mercruiser-22-806608a02-8m2000874-5-pack.aspx

I have Stainless Marine water pumps with the stainless plugs, so I contemplated this (although I have like 20 of the blue plugs in my spare parts box ha). My understanding, based on this chart, is that a stainless plug in a cast iron block will cause galvanic corrosion?

Grabber | Technical Data

www.grabberman.com

 

[alldodge]

Yes, sort of.
The chart shows there is an issue but does not show how much. The plugs screw into Bronze/Brass fittings. The Brass is screwed into cast iron, so we have Brass to Cast already and were discussing the Brass to Stainless.

This chart shows more of the degree of an issue using copper as the base.

 

[Bondo]

I have Stainless Marine water pumps with the stainless plugs, so I contemplated this (although I have like 20 of the blue plugs in my spare parts box ha). My understanding, based on this chart, is that a stainless plug in a cast iron block will cause galvanic corrosion?

Ayuh,..... Maybe over time, but drain plugs are Usually pulled annually,....

If yer concerned, coat the threads with perfect seal,....

 

[PremierPOWER]

Ayuh,..... Maybe over time, but drain plugs are Usually pulled annually,....

If yer concerned, coat the threads with perfect seal,....

Maybe on the raw side, although I don't since I take the boat to Florida in the winter. I'm not sure why anyone would pull the plugs on the coolant side annually?

 

[alldodge]

Could even say way does Merc put plastic plugs on the closed AF side. Should just have brass plugs.

 

[Lou C]

One of Merc's lousy ideas, that and all the other plastic in the cooling system. It gets hot & cold and gets brittle then you see what happens. I would not risk losing an engine over their cheapness. Replace all those plugs with metal the next time you replace coolant.
BTW I have brass (I think) plugs in my old 4.3 they get removed yearly for winterizing and coated with OMC Gasket Sealer or Permatex Aviation whatever I have on hand and I've never had one seize up. And that's with all salt water use. If I had a modern Merc engine that's the first thing I'd toss. Plastic doesn't belong screwed into engine blocks!