hey there dangos jr. today's video is
about the past that the cooling water
takes through an outboard power head and
is probably sponsored by marine engine I
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think most people are pretty familiar
with the path the cooling water takes
from the leg down those side grills up
into the water pump through the impeller
then up the water pipe to the power head
but I think it gets a little bit more
mysterious after that so that's what
we're going to be focusing on today what
I've got here is the power head from a
Yamaha two-stroke 2 cylinder probably
about a 15 horsepower or something like
that quite remember where it's from and
we're just going to sort of take the
part and have a look at the actual path
the water follows so once the cooling
water comes up from the pump it enters
this particular outboard block down here
so Salus the water comes up to this
little opening here and when it comes in
under this exhaust cover so we'll be
taking that off as well
I also just remembered where this
outboard came from it was a Yamaha 20
that had thrown a bearing and put the
rods through the side of the block this
is the exhaust cover here and this
little barb here is where the hose for
the telltale comes from so we've got
this cover nothing particularly special
about it and the outlet here this outlet
for the tell-tale isn't actually from
this cavity here this telltale outlet
from this side comes through actually to
this flange surface and picks up from
below here as well so we'll actually
work a little back we'll go inside here
and then I'll show you the part that
takes before it comes back out that hole
these have always got gaskets and things
on the monster they're missing in this
case because it's been pulled apart but
we've got this kind then underneath here
we've got the exhaust ports from the
outboard so these shapes here are just
designed to deflect the gases to give it
a sort of a smooth curve to flow so you
don't get that turbulence quite a bit
goes into design in this side of a
two-stroke motor because in order to get
those exhaust gasses out it needs quite
a specific shape to the exhaust whereas
with a four-stroke it's simply that
Pistons sort of pushing exhaust gasses
out before we move on though I will show
you one other thing to do with this
exhaust which is there's two little
openings here and here and with this on
you can see that inside this other cover
that opening here goes through this
little gallery when this covers on this
port here is connected to this port here
through this little sort of convoluted
gallery and this port here we take this
head off inside the cylinders here
you've got your intake and your exhaust
port your exhaust ports the one on this
side here heading over to here this
one's actually missing a huge chunk you
can see the cylinder walls broken but
then you can see this little port there
we go a little round on there in front
of a torch so if we come back to these
two ports the main exhaust port and this
little hole here you'll see this little
hole if I shine the torch through it
comes out through that little hole so
this little gallery here is a path that
connects this little exhaust port with
the main exhaust port there and I'm sure
somebody who's really into two strokes
will be able to comment and tell us
exactly why that is because I've got no
idea
anyway I'll stop telling you I don't
know and tell you I do know which is
about the cooling water so when the
water comes through here one of the
first place that can go is come out
through this hole here so I'll show you
where that then leads so you can
hopefully see that that's directly
connected light shines straight through
there they can come up into the top here
once cooling waters come through here up
here and onto the top here you can go
down all these little holes we just saw
so one of them is this one here if I
come round this way and show you and
then we shine torch down there hopefully
you can see that this one lights up so
that's actually connected
like nothing more complicated than being
a single space here so once waters gone
down here the pressure forces it out
here and that's the outlet for the
tell-tale so if you're telltale is
running what it's telling you is that
water's coming up from the block it's
coming through here it's coming down
here back out here and out the tell-tale
that's not enough to call the motor so
that's why having your telltale working
till she your pumps pumping water but it
doesn't tell you that your motors
actually being cooled by that water so I
think that's really the first take-home
message from this is that a telltale is
simply an indication that your water
pumps working it's not indication that
your motor is actually being cooled so
you can have a really good telltale and
still have a motor overheating the real
job of cooling the outboard comes when
the water goes down these other holes
here because they lead to the water
jackets around the Pistons so I'll show
you your sort of shine the light and
show you how that works we've got a hole
on top here the cooling water gets to
and these were water jackets around the
Pistons so if I shine the torch in that
hole up there you can see light shining
here down goes the other one shining
down inside the water jackets if I then
take this little inspection camera and
put it inside the water jackets of this
bottom cylinder so you can see here
that's the cylinder then there's the
cylinder wall and the water jacket here
then if we go inside this water jacket
upper top because this little passage we
can go into there and we'll see and see
that light shining you take a light away
and that light is to here so we know
that's directly connected to right so
where does that get us what it means is
if we have all our cover plates on like
this we've got a good working pump what
is going to coming in here
is going to be coming on to the top here
it's going to be going directly into
this bottom jacket it's going to be
going down these Epogen to the jackets
as well it's going to be coming down
here and out the tell-tale so we'll have
water sitting around the water jacket so
there will be water there and we'll have
a flying telltale what we'll do now is
move around to the actual cylinder head
and we'll see what happens next
all our waters come in here from this
side it's free to flow and fill all
these water jackets around the Pistons
here and then it kind of stops and what
happens if I pop the cylinder head on so
once the water comes up through the
bottom here it can come up into here it
can flow through all these spaces it can
flow around here can flow right up the
sides when all this water eventually
gets to the end of the road this is
where it stops there's a little aperture
here that also just goes down in the
water jackets so water can flow up
through there as well and then it comes
up and goes into here what's in here is
your thermostat so thermostat cover
gasket goes around that and then inside
here is a pretty main key looking
thermostat but the point being the hot
water comes up to this side of
thermostat this is the side with a
little wax plug that expands with
temperature so this here is a thermostat
in its closed position and if we heated
that up this would open and allow the
water to flow but in this case it's
currently blocked off I'll go boil some
water and I'll throw this in and show
you what happens interesting to see if
it still works it's pretty monkey but it
may still work just a glass of hot water
boiling water will pop the thermostat in
and we'll see what it does
I think we can pretty much call this
thermostat dead as you can see there it
hasn't opened at all what it will do
though is just open a new one and show
you what they're supposed to do so
that's what they look like closed and
that's what they look like open and
eventually as this cools down that
little plunger will recede back in so
it's a pretty simple test you can do to
make sure your thermostats working what
it means for the flow of the water if
your thermostat is stuck clothes like
this is that water will come up it'll
come out the tell-tale all these water
jackets will fill presuming they're not
blocked with anything then the water
will get to the top here where the
thermostat is and it'll stop it'll keep
flowing at the tell-tale because it
needs to come out somewhere and you'll
have this sort of pressurized water
sitting inside the jackets and that
water will just get hotter and hotter
and hotter eventually it'll turn to
steam and you might have a bit of steam
coming out the telltale but the engine
will gradually overheat even though it
is actually surrounded by water the
purpose of the thermostat is to get a
motor up to temperature quickly so it
lets that water sit there until it's hot
enough and then when it gets to the
right temperature
it opens allows the water to flow if the
engine actually starts to get too cool
it'll just close again it just regulates
the temperature so it gets it to a
temperature quick and then it keeps it
at that correct temperature the whole
time thermostats will often have the
temperature printed on the temperature
they're designed to open it so if we
look at this one hopefully you can see
they're 50 degrees Celsius is when this
one opens I'll bring you in close again
and just sort of show you the final
piece of the puzzle now so cooling water
was coming up here to the thermostat the
thermostat opens this little cover just
provides a part of the water to loop
back over so the work comes out the
thermostat and then back down here
that passage simply comes into here it
runs down the other side when the water
gets to the bottom here it goes down
this hole and therefore shine light
through here we can see that light
coming out to places inside the casing
and then down here that goes inside this
exhaust manifold and this is where the
exhaust comes out here this is the
exhaust for this outboard and if we
imagine this bolted on here this outlet
here comes into here which actually just
goes straight to here and then it flows
down the outside so it looks like it's
designed to run down the outside of the
exhaust to keep it cool it doesn't
actually go through the center so I hope
this video helps you understand the path
but what it takes and I hope that
knowledge of the path to what it takes
will help you diagnose overheating
problems if you're having them a good
tool towel just means your pumps working
and a working pump means nothing unless
you've got a working thermostat taking
the thermostat out means the motor is
going to be running cool all the time
it's better than the motor overheating
you know this failure may have actually
been due to that thermistor being stuck
so if the thermostat wasn't there child
status motors still be working but if
you take the thermostat out it's going
to be running cool your efficiency is
not going to be good your fuel
efficiency you might find your plugs
foul up your emissions won't be as good
it's not ideal to have no thermostat in
a boat I wish I'd filmed it but I
actually had a boats in the shop at the
moment that was overheating it had a
good telltale and the thermostat was
working and if I took the thermostat out
ran the motor lots of water was coming
out the thermostat hole so in that
situation I'm normally pretty confident
that cooling is working properly if you
can take the thermostat cover off and
water's coming out the thermostat and
you know it's good themselves actually
brand new something else is going on so
I took the hit off that motor and this
is what I found there was a big chunk
here missing from the cylinder wall now
oddly this actually had perfectly even
compression on both cylinders so go to
show compression tests are a little bit
hidden miss but it was obviously a
problem here
now another big clue to it was the
nature of the tell-tale the tilt I was
actually quite forceful and was a little
bit sporadic in its kind of pulses and
what that is is exhaust gases coming
past this cylinder water'll blown head
gasket and displacing all that water the
water was being pumped in by the pump
but then the exhaust gasses were much
stronger and they were just pushing
exhaust gasses into the water jackets
flashing net water out with such force
was actually flowing all the way
backwards and pushing these gases out
the tell-tale so that's a really good
sign of a blown head gasket
so although the cooling system on this
motor was working perfectly good pump
good thermostat no blockages it was
actually the blown head gasket that was
causing this motor to overheat well I
hope you enjoyed this video I sort of
hope it solved the mystery of where all
this calling what it goes if you weren't
familiar with it and I hope that
information does help you if you're
having a problem with your outboard
because although you don't always need
to understand it it certainly can help
with your thinking when you're trying to
figure out what's going on with your
outboard alright we'll take care of and
I'll see you next week
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