Merc. MPI 300 Water Leak-Water Distribution Housing? & Winterization Question

[ck82]

Hey All,

I started up my Monterey super sport this spring here and realized I had a water leak. I've attached a video of a slow drip from the Water Distribution housing. I pulled the hoses and inspected the distribution housing and it appears neither have any cracks or leaks. Looking into the parts diagram it again appears that the closest part to the distribution housing is a fuel supply module.


Last fall, I winterized the engine as required, however I did not pull the few drain blocks on the block and distribution housing. I also did not utilize the air actuated drain system. The prior years I had, however I assumed that after running RV Antifreeze/Glycol through the system I would be fine.

Please let me know your thoughts, and what steps to take at this point.

Engine: Mercury MPI 300

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[alldodge]

Up load you movie on Youtube

 

[achris]

however I assumed that after running RV Antifreeze/Glycol through the system I would be fine.

How (exactly) did you add AF to the engine? (pull the thermostat housing and pour it in or suck it up on the flushers?)

 

[ck82]

I installed the earmuffs on the lower unit, ran the engine until the boat was up to temp and the thermostat opened, then switched over from hose water to my RV antifreeze jug. Suck through maybe 3 or 4 fgallons once it spit out the exhaust i shut the engine off.

 

[alldodge]

I installed the earmuffs on the lower unit, ran the engine until the boat was up to temp and the thermostat opened, then switched over from hose water to my RV antifreeze jug. Suck through maybe 3 or 4 fgallons once it spit out the exhaust i shut the engine off.

Not good.
When the motor gets up to temp, this only means its at running temp, it does not mean the thermostat stays OPEN

The thermostat opens and closes for very short periods. Adding AF once up to temp means only it gets diluted by water. In the spring after a cold winter your almost guaranteed to have a bust block

To winterize a motor, first pull all the drain plugs (block, fuel cooler, exhaust) and stick a wire or screw up through the hole to make sure everything drains out. One piece of crud blocking the drain hole will cause trouble in the spring.

Once "ALL" the water is out you are winterized. Air does not freeze so you good. If you want to add AF, now is the time if your want to. Its best to add AF by installing the drain plugs, then removing hoses from the thermostat housing and filling hoses with AF, then reattach

 

[ck82]

Not good.
When the motor gets up to temp, this only means its at running temp, it does not mean the thermostat stays OPEN

The thermostat opens and closes for very short periods. Adding AF once up to temp means only it gets diluted by water. In the spring after a cold winter your almost guaranteed to have a bust block

To winterize a motor, first pull all the drain plugs (block, fuel cooler, exhaust) and stick a wire or screw up through the hole to make sure everything drains out. One piece of crud blocking the drain hole will cause trouble in the spring.

Once "ALL" the water is out you are winterized. Air does not freeze so you good. If you want to add AF, now is the time if your want to. Its best to add AF by installing the drain plugs, then removing hoses from the thermostat housing and filling hoses with AF, then reattach

Not good.
When the motor gets up to temp, this only means its at running temp, it does not mean the thermostat stays OPEN

The thermostat opens and closes for very short periods. Adding AF once up to temp means only it gets diluted by water. In the spring after a cold winter your almost guaranteed to have a bust block

To winterize a motor, first pull all the drain plugs (block, fuel cooler, exhaust) and stick a wire or screw up through the hole to make sure everything drains out. One piece of crud blocking the drain hole will cause trouble in the spring.

Once "ALL" the water is out you are winterized. Air does not freeze so you good. If you want to add AF, now is the time if your want to. Its best to add AF by installing the drain plugs, then removing hoses from the thermostat housing and filling hoses with AF, then reattach

Shoot, doesn't sound good that's for sure. I've attached a video with the muffs installed and the water running. There is a consistent drip with the engine off. With the engine running there is definitely more water flowing/leaking.

I have taken the cooling hoses off the water distribution housing and looked the hoses and distribution hoses over for cracks. I didn't see anything visible.

Should I hook everything back up and run the engine and see if I can locate a leak from the block?

*The leak is shown right away dripping from the distribution housing.

 

[alldodge]

Not sure, but looks like its comming from the water distribution housing. Those housing do crack. A member here made one from copper piping

 

[Scott Danforth]

There are no shortcuts in winterizing. Drain the cooling system an pressure test

 

[achris]

I installed the earmuffs on the lower unit, ran the engine until the boat was up to temp and the thermostat opened, then switched over from hose water to my RV antifreeze jug. Suck through maybe 3 or 4 fgallons once it spit out the exhaust i shut the engine off.

You successfully winterized your exhaust manifolds, and nothing else. If all you broke was the water distribution housing, consider yourself extremely lucky.

Chris.......

 

[ck82]

The distribution housing doesn't look cracked or comprimised, its possible though.

I will look into pressure testing an open cooling system as Scott Danforth stated as well.

 

[achris]

The distribution housing doesn't look cracked or comprimised, its possible though.

I will look into pressure testing an open cooling system as Scott Danforth stated as well.

Those housings are plastic. You only have to look at them to have them break. Something I'll be doing the next time my engine is out is to completely do away with that terrible system. It's not hard to just redirect the water and go back to the old system. Given you are going to be pulling the system out to repair it, I wouldn't. Just remove it completely and go back to the water hose from the transom going straight into the t-stat housing (like they used to)...

Chris......

 

[Scott Danforth]

Just remove it completely and go back to the water hose from the transom going straight into the t-stat housing (like they used to)...

Chris......

Best advice ever. And the sad thing is most of the engineers at Merc would agree

 

[nola mike]

Anybody have a diagram? I don't see that design in manual #25 (most recent I have)

 

[achris]

Anybody have a diagram? I don't see that design in manual #25 (most recent I have)

For the newest (single point cracking) system?

Had another look at my engine this morning (winter here, so it's a bit cold out, I had to put shoes on )... and this crack system would be so easy to re-route. Here's the system as it is supplied. (this is the V6, the V8s are the same)



Here's it re-drawn as I'm going to do it. Remove the 'drain' hoses (2 from the engine block, replace with standard 1/8" gas plugs. 2 from the manifolds, replace with brass 90° elbows), replace the water distribution housing with a 90° tube, move the 'excess' water dump that was on the WDH onto one of the water manifold ports. Completely do away with the rod and all its associated mounting hardware.

 

[ck82]

Hey Fellas,

I re-connected the cooling hoses to the distribution housing and to the raw water crossover cooling assembly this morning. I wanted to start the engine and further look into where the leak was coming from now that I took the cover off the front side of the engine compartment, so I can see much easier below.

I started the engine up with the muffs connected and water running. The boat ran for close to 10 minutes, I was watching the digital thermostat on the medallion display and it wasnt getting up to operating temp. It seemed like things were getting hot so I shut the engine off. From there I pulled the water distribution plug and no water came out. I then pulled the water crossover cooling assembly hose, went and grab some buckets of water and poured a few down in.

From there I re-installed the cooling hose and started the engine. Nearly immediately an alarm sounded and the digital thermostat shot up a little over half way, so I shut it down immediately as well.

I dont understand why the thermostat didn't open as the engine was obviously getting hot, and the gauge didn't rise initially. Then once I shut it off and added water to the crossover cooling hose, started the engine, the temp gauge shot up and an alarm sounded.

When I filled the cooling hose with water, water did begin to drip again from the bottom of the water distribution housing similar as in my video I posted earlier on.

My boat is in my garage with the bow facing out and slightly downhill, thus I'm wondering if my water leak is further back and its running down a hose and off the bottom of the water distribution housing, since its the lowest point on the port side of the engine.

I know I'm an idiot and will deal with that, however any insightful information at this point would be appreciated.

Thank you.

 

[ck82]

Update here. I pulled the drain plug from the seawater pump and felt a piece of plastic or rubber inside. I used a forceps like for fishing and stuck it into the drain plug hole, pulling out a few pieces of rubber from the seapump impeller. I just removed the pump assembly and yes the impeller is destroyed. I'd say that is my issue as far as the block not circulating water.

A few questions stemming from the impeller failure.

-Should I just order the impeller kit, or do I have other things to worry about, and should instead order the entire assembly? I would think just the impeller kit would be sufficient, as its just rubber impeller that failed?

-Since there's possibility that some of the broken apart impeller has made it into the cooling hoses and I guess possibly into the block, how would I flush the block to possibly dislodge and push out any fragments of rubber? I would imagine I would need to remove the various hoses from the block and try to flush it back the way it came? Any insight on this would be appreciated.

Thank you for any info.

 

[alldodge]

When pieces are found its best to back flush everything

If the impeller is not moving water then it needs to be looked at and determine if it needs replacing

Was the thermostat installed correctly?

 

[ck82]

Any idea of where to start as far as back flushing? I only will be able to get to certain hoses on the front of the engine.

Should I pull the crossover cooling assembly hoses and run water through, hoping it pushes out the seawater pump hoses?

The boat is a 2017, so fairly new. The T stat worked fine previously, and it seemed to work all but when I was running the engine for earlier today. Maybe that is because no water was circulating through the block and so on?

Hopefully running it hot for a brief time today didn't cause any further issues. The warning signal didn't go off until when I started the boat up a second time. Thats when the t stat seemed to work as the digital gauge moved.

 

[alldodge]

You have closed cooling I take it???

What is your serial number?

 

[ck82]

Open cooling system.

Ser. #: 2A578724