Will a cracked manifold cause this?
 

Hey all a buddy has a Mercruiser 140hp IO, it has a cracked intake manifold
and is leaking water out the side. He thought that he could run it like that
for the summer and just replace it this fall. Well the problem is, is that
it wont idle. It runs fine above 1500 rpm. Below that it just dies. We have
tried adjusting the mixture needles on the carb, verified timing, rebuilt
the carb ( did this first, the boat sat for 10 years before he bought it).
Im thinking that since the outer case of the manifold is cracked and activly
leaking, that its possible that the inner manifold is also cracked and
leaking either exhaust into the intake or even slight amounts of water into
the intake. What do you guys think
Thanks
Steve

Will a cracked manifold cause this?
 

YES

"seeray" wrote in message
...
Hey all a buddy has a Mercruiser 140hp IO, it has a cracked intake
manifold
and is leaking water out the side. He thought that he could run it like
that
for the summer and just replace it this fall. Well the problem is, is that
it wont idle. It runs fine above 1500 rpm. Below that it just dies. We
have
tried adjusting the mixture needles on the carb, verified timing, rebuilt
the carb ( did this first, the boat sat for 10 years before he bought it).
Im thinking that since the outer case of the manifold is cracked and
activly
leaking, that its possible that the inner manifold is also cracked and
leaking either exhaust into the intake or even slight amounts of water
into
the intake. What do you guys think
Thanks
Steve

Will a cracked manifold cause this?
 

"seeray" wrote in message ...
: Hey all a buddy has a Mercruiser 140hp IO, it has a cracked intake manifold
: and is leaking water out the side. He thought that he could run it like that
: for the summer and just replace it this fall. Well the problem is, is that
: it wont idle. It runs fine above 1500 rpm. Below that it just dies.

The crack lets air in, which leans out the mixture. Running it as lean
as he is considering the symptoms you write of, will hole a piston
and burn exhaust valves in very short order.

Dave