Leak from somewhere?

M Prod

Well-Known Member
Oct 6, 2017
1,438
North Vancouver, BC
Boat Info
2005 Sundancer 340
Zodiac Cadet w/FCT console Yamaha F20
Kohler 5KW Genny
Engines
8.1 Horizons /V Drives
Hey gang ..I’ve got a leak presumably from somewhere in the raw water cooling side, but I can’t seem to reproduce it at the dock. It seems to be coming from down low somewhere, and has been going in long enough that it’s badly rusted the exterior underside of my starboard inside manifold. At the dock, I run the engines and rev them up to about 3000rpm, but there is no water spray. I had cleaned this up and tightened some hoses and painted the manifold, but after having it out today for an hour, the underside of that manifold is white with salt. Leads me to believe that this is only happening when the boat is in gear. Could it be related to a shaft seal? Why is there no water spray while at the dock in neutral? Any ideas?
 
Here’s a pic of the starboard inside manifold. It has a clear line of sight to the port shaft seal from there. This is the section taking the bulk of the spray

5EB551E9-D960-4AD9-B6B2-AC645C852A36.jpeg
 
Is this the only place you are noticing this? Also want to confirm that this is the forward side of the engine compartment (opposite of belts) and rear of engine. Do you see water anywhere? I am guessing the salt is because the water evaporated off the manifold.

-Kevin
 
Dwna1a ..yes FW cooled, but this isn’t in the area of the heat exchanger. Opposite end.

Kevin ..yes on all. This is by far the most severe area. I don’t see any water under the port engine, and the diapers under starboard are damp. Leads me to believe this isn’t from the port at all. There was a little salt on top of the block but just a little. It’s mostly hitting the underside of this manifold. I’m thinking it might be the shaft seal cooling hose since there was no spray when in neutral. Does water flow to the seals when in neutral? I’m at a loss since there was no spray at the dock with engines revved to 3000rpm. I only ran one engine at a time though ..maybe need to run both.
 
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Was the manifold wet in top? They are normally cool to the touch but hot where they meet the block. So, I was wondering if it's a top down leak that could be running down the side of the manifold.

The shaft seals do need water to keep them lubricated and cool. (http://www.clubsearay.com/index.php?threads/why-does-water-come-through-the-shaft-seal.37837/) so it could be a source.

Maybe you can put it in gear tied to your dock so you get a peak. Otherwise your gonna need a helper at the controls while your down there.

-Kevin
 
Completely separate issue, but just a point...

It’s obviously something that happens under pressure. I was having water spray all over the front of my port engine. Turned out to be the water heater that had a pinhole leak.

Perhaps the leak is nearby and aimed toward the concerned area.
 
Yeah I guess I just need to investigate more. I actually might have to replace this manifold which is a shame as it’s less than a year old. Not sure how much it’s rusted. There’s no hole in it ..yet, but it looks pretty bad from here. I’ll get someone to take a ride with me so I can get in there and find out what’s what.
 
You can see a crack in your picture that wet spot. It is a heat related crack or dirt was in casting when it was porred. When engine get hot the crack opens up and when cooler it seales back up it happens on home hotwater heaters a lot.
 
That would definitely not be the best case scenario, but this seems like excessive rust for a leaky hose hitting it. I thought the crack just a layer of rust peeling, but maybe you’re right. Hard to tell from pics I know. Here’s another I took with a flash. You can see where a large piece of rust near the bottom flaked off. It’s an OEM Merc manifold installed last March ..so if it is in fact the manifold itself, I’m sure there’s some warranty claim here.

43221B95-E97C-4237-9141-D5E205C58C83.jpeg
 
I sent these pics to a mechanic friend, and he believes it to be a crack in the manifold as well. I'll do a sea trial with him later in the week to see if we can get them hot enough for the crack to open. In the meantime I've emailed Michigan Motorz as I believe there is a 3 year warranty on Mercruiser Manifolds. Glad this is happening in January and not July. Stay tuned ...
 
Update ..can’t for the life of me find a water leak. I cleaned the manifold up again and even painted it, took the boat out, and when I got back the salt had once again accumulated in this area. No water or wetness anywhere ..no sign of spray, no salt anywhere else ..just a heavy coating of salt crystals on this area of the manifold. I’m at a loss. What I worry about now is that water is getting ingested into the engine seeing as there’s no water jacket in this area of the manifold. I really have no idea what’s going on. Mercruiser and Michigan Motorz are asking me to pressure test the manifold to see it it is in fact a leak. I guess that’s the next step.

Here’s more photos I took of the bottom of the manifold after I had her out Monday. This was after I cleaned the salt off.

15309F9D-9B45-4AF7-AF22-BDD05B7C21C6.jpeg



20FFF67E-74A3-4D4C-9151-3337FE8DB5A7.jpeg
 
That manifold looks burned, like a hot spot. I hope that's a paint chip line, looks like a crack in that first pic.
Have you tried having someone run the boat while you examine for leaks?
If no water is making it into the bilge, I'd be thinking hairline crack in manifold or somewhere close by.
 
Update ..can’t for the life of me find a water leak. I cleaned the manifold up again and even painted it, took the boat out, and when I got back the salt had once again accumulated in this area. No water or wetness anywhere ..no sign of spray, no salt anywhere else ..just a heavy coating of salt crystals on this area of the manifold. I’m at a loss. What I worry about now is that water is getting ingested into the engine seeing as there’s no water jacket in this area of the manifold. I really have no idea what’s going on. Mercruiser and Michigan Motorz are asking me to pressure test the manifold to see it it is in fact a leak. I guess that’s the next step.

Here’s more photos I took of the bottom of the manifold after I had her out Monday. This was after I cleaned the salt off.

View attachment 65467


View attachment 65466
 
I enlarged your second pic on my Mac. Are these by chance pin holes?
Screen Shot 2019-02-21 at 6.42.09 PM.png
 
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I enlarged you second pic on my Mac. Are these by change pin holes?
View attachment 65475

Holy S$%T. Maybe? I'm going to point this out to Merc. They keep saying there's no water jacket in that area, but if something is broken, who's to say that water isn't traveling into this part of the manifold.

Thanks ..good eye!
 
I went back and looked. Those are just shadows from the rust cavitation. Optical illusion. Here's another photo with slightly different lighting.

Side Note: It is extremely difficult to get down this low to see under it from this angle. I had to contort between the engines. Thought I was stuck at one point, but managed to wiggle and pull my way out. Nothing is easy in this engine compartment, especially for a 6'1" 200 pounder like me.


Manifold.jpg
 
That entire area looks suspect. I've see something like this before. If it's what I think it is that manifold is shot.
Its semi plugged inside. Most likely rust flakes. That is causing it to get super heated in the corner there. And that is making the iron thin and porous. So under pressure the water is squeezing out in dozens of micro places, appearing to look like spray. Since it's super heated you may never see water, but rather salt slowly building up.

Your not see this happen in your slip because it's not getting to a super heated condition. It needs a heavy load to make that happen.

Time for a new manifolds.

Good luck,
 
That entire area looks suspect. I've see something like this before. If it's what I think it is that manifold is shot.
Its semi plugged inside. Most likely rust flakes. That is causing it to get super heated in the corner there. And that is making the iron thin and porous. So under pressure the water is squeezing out in dozens of micro places, appearing to look like spray. Since it's super heated you may never see water, but rather salt slowly building up.

Your not see this happen in your slip because it's not getting to a super heated condition. It needs a heavy load to make that happen.

Time for a new manifolds.

Good luck,

Thanks. It’s just that these manifolds are less than a year old. The other three appear to be fine. I suspect it’s a defect of some sort on this particular one. Proving that to Merc is going to be a challenge.
 
Thanks. It’s just that these manifolds are less than a year old. The other three appear to be fine. I suspect it’s a defect of some sort on this particular one. Proving that to Merc is going to be a challenge.
Wow, one year. Must be a bad casting. But I think my theory is right. It's getting cooked for some reason. Hopefully that cylinder is running lean.
 

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