Water leaking behind exhaust manifold on Mercruiser 140

[86Crestliner]

Hello All, New to the forum and boats. I'm not foreign to working on all types of enginges, just never marine engines.....

Problem is, I have water leaking while the engine is running behind the exhaust manifold. All freeze plugs are in place and I just can't pin point where it is coming from. What should I look for, could it just be a manifold gasket?

One more thing, I just bought the boat and don't believe the oil was changed this year. What type and how much oil should I be using in this motor? Is there any preventative maintenance I should perform on the outdrive?

Thank you all in advance for any information you can provide!!!!

-Mike

 

[ryanr623]

Re: Water leaking behind exhaust manifold on Mercruiser 140

Its leaking from the engine, or from the back of the boat?

As far as oil, everyone will tell you different things.

Since you only boat when it is warm, a lot of people reccomend straight 30 weight oil. Others will reccomend multi grade oil. I find 20W-50 has a good blend of wear protection and viscosity.... at least from my research.

I would advise against rotella straight weight oil. Have heard a couple bad things about rotella recently.

 

[sqbtr]

Re: Water leaking behind exhaust manifold on Mercruiser 140

Sounds like a cracked block. Check it with a mirror and flashlight

 

[zbnutcase]

Re: Water leaking behind exhaust manifold on Mercruiser 140

There is no water passages between the manifold and head. Most common reason is freeze crack in block or manifold. As for oil, I like 30w Delo 400. How much? Until it reaches the full mark on dipstick.

 

[86Crestliner]

Re: Water leaking behind exhaust manifold on Mercruiser 140

Thanks guys, that's what I was afraid of Hopefully its a small crack and can just marine tex it. Is JB Weld basically the same thing as Marine Tex or should I just stick with M tex? That is if it needs it....

 

[antsmands]

Re: Water leaking behind exhaust manifold on Mercruiser 140

Thanks guys, that's what I was afraid of Hopefully its a small crack and can just marine tex it. Is JB Weld basically the same thing as Marine Tex or should I just stick with M tex? That is if it needs it....

I repaired my block crack (did not winterize) with JB Weld and its working fine. I used both the 2 part JB weld epoxy and the the putty to assure a good tight seal. Be sure to drill both ends of the crack to prevent spreading, vee out the crack with a dremel or similar tool and really clean and roughen the surface a minimum 1in around the entire crack. A few small drill hole distrinuted across the crack will also help the epoxy hole in the vee but not to many. Mix the JB weld and apply a good uniform coat over the entire crack area, allow to set up and apply the JB putty before it is cured to get a nice tight double layered bond. I then spray painted it with black engin paint. As for the oil I use Castrol 30W in my boat. Works great. Hope this helps!

Tony D.

 

[86Crestliner]

Re: Water leaking behind exhaust manifold on Mercruiser 140

Thanks Tony, that'll be a huge help!

 

[180shabah]

Re: Water leaking behind exhaust manifold on Mercruiser 140

You need to find the leak before you oplan a repair strategy.... If the manfold is also cracked internally, you cannot repair it. and it will destroy you engine if not addressed NOW.

oil - merc recomends 25W40 - if you don't want to use that, use whatever you want.

other things to "check"
engine alignment
bellows
gimble bearing
ujoints
seawater pump
drive gear lube
tstat
plugs, cap, rotor, points(if applicable)
fuel filters
water seperator (add one if you don't have one)
battery condition including all connections
bilge blower
bilge pump
lights - ALL

 

[86Crestliner]

Re: Water leaking behind exhaust manifold on Mercruiser 140

I looked up underneath the manifold with a flashlight to see where the water was coming from. Without the engine even running, there is water dripping from the top of the block behind and toward the center of the manifold. Guess I need to pull the manifold off and see just how bad it is.

 

[180shabah]

Re: Water leaking behind exhaust manifold on Mercruiser 140

Guess I need to pull the manifold off and see just how bad it is.

No other way....

 

[woosterken]

Re: Water leaking behind exhaust manifold on Mercruiser 140

other things to "check"
engine alignment
bellows
gimble bearing
ujoints
seawater pump
drive gear lube
tstat
plugs, cap, rotor, points(if applicable)
fuel filters
water seperator (add one if you don't have one)
battery condition including all connections
bilge blower
bilge pump
lights

????? will all these also cause his water leak ?

woosterken

 

[180shabah]

Re: Water leaking behind exhaust manifold on Mercruiser 140

????? will all these also cause his water leak ?

NOPE, but they do address the other part of his question - some of which have the potential to save him thousands vs component failure.

Is there any preventative maintenance I should perform