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3.0 TKS leaking manifold

tmarshallg

New member
Video link attached to the bubbling/steam coming out of top of motor beside manifold.

Seams to be a failure in the exhaust manifold gasket. Cooling lines seemed clogged initially, when running off hose no water came out the exhaust but it never overheated. I then throttled up to try and pop out whatever could have been “clogging it” and then seconds later water began coming out the exhaust along with a large puff/cloud of white smoke. The smoke cleared shortly after. Cooling lines seemed fine then. Have noticed some black particles discharging from the water drain/winterize hoses when I drain after use.

While on the water I noticed this coming out of the top of the manifold gasket. Engine was brand new installed from a crate motor in June of 2017. This could have first occurred today, or been occurring for a while but I didn’t own the boat till two months ago. It’s only been run in fresh water to my knowledge, and it’s all I’ve run it in.

I’m not a mechanic, and this is my first boat but a big DIY guy. I’ve read enough to know a bad manifold can leak water and cause serious damage.

https://www.youtube.com/watch?v=XvcPYz4txa8

 
BTW the boat is a 2006 Maxxum 1800MX. It sat for 9 years and had a new engine block installed in it last year so I really want to do something to prevent any rust from forming inside the block since it's brand new practically. Can I spray WD-40 down into the cylinders somehow? The oil has no water in it and still very clear/new looking. I changed it last month.
 
Pull the manifold off and inspect it. Inspect the head....You will be looking for a crack....There are no water passages between the head and manifold where they connect.

Important Question........What happened to the last engine?
 
Does anyone have a good guide for removing the manifold, and then replacing? I'm sure there are some secrets like what high temp RTV to use, ft lbs for all the bolts, easiest way to remove carb off manifold, etc.

I just can't imagine how it cracked... I feel like it's got to be the manifold gasket failed, or hope. I did check the compression on all 4 cylinders and the were an even 150 across all 4. Can this at least assure me the block is not cracked? I'm not a mechanic in anyway, but have fun learning so trying to keep the project minimal.

Should I do anything to prevent furthering rust, like spray WD-40 inside the cylinders?

The boat sat for 8 years and ethanol, rust, etc must have destroyed the original motor. It was an older man who passed away and his wife finally sold it last year. I wasn't involved in this process as the owner before me then decided to sell it after the repower because boats cost too much to maintain. I hope this baby isn't a lemon! Unfortunately it sat uncovered so the seat vinyl took a beating, but other than that the boat is in great shape!

Any experience with aftermarket manifolds, like the Sierra?
 
No aftermarket parts.
Like I said, there are no water ports sealed by a gasket between the head and the manifold.

Take you serial number and head to your local Mercruiser dealer and get the factory service manual.

Was the water pump serviced in the outdrive by someone who knows what they are looking at? If there was an issue with the lower unit, where the water pump is, and it was not addressed with the new engine, it will crack the new engine cylinder head.
 
If I had to guess, I would guess that you have a crack in the cylinder head. The black bits you see are likely fragments of water pump impeller. Unfortunately, you are in for an expensive repair no matter how you slice it.
This is why you pay for a licensed surveyor to look it over prior to the sale. A couple hundred bucks and you would have known about this (and walked away). Now you have a (possibly couple) thousand dollar problem.
 
The water pump was supposedly replaced or inspected last year when they were replacing the motor. The water pump appears to be working quite well as it was flowing like crazy out of the thermostat. (I disconnected the water hose going from thermostat housing to manifold and ran for 30 seconds to dry out and moisture that could have leaked in cylinders from manifold). I don’t think the pump is bad. I think the black particles is maybe black paint residue from the brand new parts. I guess it could be the water pump but like is said it was gushing out water like crazy. Filled a 4 gallon bucket in about 20-30 seconds

how noticable will a crack be in the manifold or head if I inspect myself?

where can I find the serial number on this block, and what would the number letter sequence look like?
 
serial number is on a tag just above the starter unless it is just a replacement motor not from mercruiser.
I have had manifolds completely clogged with sand and ones that did not drain completely because of the sand.
Typically, remove the fuel line, associated wiring, shift cable, throttle cable , maybe 4 studs and 2 nuts and manifold slides off the studs. Most times removing the riser first makes the job easier, just remember to drain everything first.
This should help
http://www.boatfix.com/merc/Servmanl/13/13C6R2.PDF#[0,{%22name%22:%22FitR%22},-82,284,695,797]
 
serial number is on a tag just above the starter unless it is just a replacement motor not from mercruiser.
I have had manifolds completely clogged with sand and ones that did not drain completely because of the sand.
Typically, remove the fuel line, associated wiring, shift cable, throttle cable , maybe 4 studs and 2 nuts and manifold slides off the studs. Most times removing the riser first makes the job easier, just remember to drain everything first.
This should help
http://www.boatfix.com/merc/Servmanl/13/13C6R2.PDF#[0,{%22name%22:%22FitR%22},-82,284,695,797]
Super, doesn't sound as complex as I was thinking it could be. Once removing the manifold and other parts, must those gaskets be replaced or reused? Any specific kind of RTV/similar I need to apply before reinstalling parts?


I mean the intake water pump not the circulating pump on the front of the engine.
The pump on the stern unit? I plan on replacing that regardless once I solved my problem for preventative maintenance reasons, then I won't have to worry this summer. Assuming my block isn't cracked! :)
 
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