Hi,

Sorry, but asking dumb questions is the only way I know of to get
smarter!! ;-)

I have a '79 Yanmar 2QM15 on my Hunter 33 that runs smoothly at some RPM
and clanky at others, with black smoke at start up and sometimes for a
while with heavy loads. I noticed very tiny air bubbles and a very small
amount of oil dripping from the head gasket just under the forward cylinder.

Not sure how many hours the motor has on it. It starts kind of hard too
but seems to be improving the more I run it. Anyway, I'm afraid to put
too much money into the motor because I don't know what shape the bottom
end is in. I have a guy who will change the gasket for $300, $85 for all
the gaskets.

Anyway, is it surely bad to run the motor much with the gasket like
that? Must I change it ASAP? I want to take the family cruising around
on some easy cruises this weekend. We have a backup motor. Bad idea? Any
other advise about what I should look for during the head gasket change
when I finally do it?

Thanks for any help!




--
Stephen

I'd change it ASAP, but for the heck of it, remember..you can't tear up
junk

I'd pull the valve cover first, and re-torque the head bolts. it's
possible that the bolts at the front of the head may have come loose or
have probably streached. that wouldn't be a permanent fix by any means.
but should "get you by" for a while. But don't stall a good repair. I
can understand that you don't want to put a lot of money in an engine
repair, but then again, you don't want to ruin an expensive head
either.

Those engines have a very tough lower end

These are great engines. You could probably put a whole top end on
for less than buying a new one and run it for years more. It isn't
just the engine cost. Changing beds, cable and hose routing, prop,
etc. will add up very fast. A top end may look expensive but not when
you compare it with the full cost of an engine change. You have a
good chance of getting away with just a head gasket and maybe a valve
job.

Are you sure it isn't a 2QM20? (Which was actually 15 shp). If so, I
have the service manual and could send you some scans of the cylinder
construction.

Even if salt water has gotten to the cooling passages, a new top end
will take care of that.
--

Roger Long



"Tim" wrote in message
oups.com...
I'd change it ASAP, but for the heck of it, remember..you can't tear
up
junk

I'd pull the valve cover first, and re-torque the head bolts. it's
possible that the bolts at the front of the head may have come loose
or
have probably streached. that wouldn't be a permanent fix by any
means.
but should "get you by" for a while. But don't stall a good repair.
I
can understand that you don't want to put a lot of money in an
engine
repair, but then again, you don't want to ruin an expensive head
either.

Those engines have a very tough lower end

Stephen,

I would change that head gasket now. The engine sounds like it needs
injector work as well, outside possibility of the injector pump, but
it's probably fine. If the engine's got good oil pressure the bottom
end is probably fine, normally, if a diesel is gone it's because of
bearing wear or piston wear, or both. The fact that the engine puts out
black smoke, rather than heavy white smoke, suggest the compression is
good, but the injectors are probably leaking down or not spraying
properly. If you have good compression and good oil pressure the engine
is probably worth fixing. You would be amazed just how many diesels are
replaced because the owner thinks it's gone, when all it needs is a
little work.

If I were you I would check the oil pressure, if it's good, have the
head gasket replaced (check it to see if the head is flat and does it
need to be rebuilt). While the head is being worked on have the
injectors removed and have them checked and replaced or repaired at the
same time.

John

Change the gasket NOW, dont wait for the cooling water to drain into
the combustion chamber and start corroding the piston ring seats,etc.

When you shut down, the hot combustion chamber will cool and if the
valves are closed will create a vacuum that will draw the water into
the combustion chamber .... then RUST.

While you're at it, remove the injectors and SEND or TAKE them to a
specialty automotive shop that rebuilds injectors for inspection and
rebuild if needed. Injector shops are common. - just have to search
them out.

Also be aware that the fuel nowadays has a much lower cetane number as
when this engine was designed; consider adding a 'cetane booster' to
the fuel. Cetane booster and reset injectors will remove most of the
'sooty exhaust' ... warming up the engine to full operating
temperature before applyling full throttle will also help. Nothing wll
make an engine smoke more than a cold combustion chamber.

hope this helps.

"Capt John" wrote in
oups.com:

The fact that the engine puts out
black smoke, rather than heavy white smoke, suggest the compression is
good, but the injectors are probably leaking down or not spraying
properly.

Or, as this is a naturally-aspirated diesel, he's got too big a prop on it
loading the hell out of it and it's running out of air before the charge is
burned...rich. Black smoke is common on an overloaded Yanmar. The 3GM on
the Endeavour would smoke like mad if you crowded it hard....(c;

Thanks everyone for the answers!

Tim wrote:

I'd change it ASAP, but for the heck of it, remember..you can't tear up
junk

Some of the other guys said it very easily might not be junk. Does this
mean I shouldn't run it for twenty hours cruising around with my family
this weekend before changing the head gasket?

In case you forgot any of the details of my engine here is my original post:

-----
I have a '79 Yanmar 2QM15 on my Hunter 33 that runs smoothly at some RPM
and clanky at others, with black smoke at start up and sometimes for a
while with heavy loads. I noticed very tiny air bubbles and a very small
amount of oil dripping from the head gasket just under the forward cylinder.

Not sure how many hours the motor has on it. It starts kind of hard too
but seems to be improving the more I run it. Anyway, I'm afraid to put
too much money into the motor because I don't know what shape the bottom
end is in. I have a guy who will change the gasket for $300, $85 for all
the gaskets.

Anyway, is it surely bad to run the motor much with the gasket like
that? Must I change it ASAP? I want to take the family cruising around
on some easy cruises this weekend. We have a backup motor. Bad idea? Any
other advise about what I should look for during the head gasket change
when I finally do it?

Thanks for any help!
------


I'd pull the valve cover first, and re-torque the head bolts. it's
possible that the bolts at the front of the head may have come loose or
have probably streached.

My half-whacked diesel mechanic seems to think there is no point in
trying this. Maybe I should insist. Or, um try it before I go on the
trip, um, because it will only take an hour or so to do?

that wouldn't be a permanent fix by any means.
but should "get you by" for a while. But don't stall a good repair. I
can understand that you don't want to put a lot of money in an engine
repair, but then again, you don't want to ruin an expensive head
either.

Those engines have a very tough lower end


Helpful, thanks! Are there any signs I should look for to shut down the
engine to avoid damage, if I live dangerously and go on the cruise this
weekend? Um, if you all recommend that, that is?

--
Stephen