My comments are inline for clarity

mrs peel wrote:
Ahoy, the mighty Yanmar YSB12 sputtered into life this evening for the
first time in many, many years. This is my first diesel and I have a
few questions. Quite a few, actually. It's kind of a long read now
that I look at it, I hope you're not too busy.
But First,..
I discovered it was seized about a year ago and added the miracle
product, Marvel Mystery Oil, to it's air inlet, pumped out the black
sludge from the crankcase and filled it with Marvel too. After rocking
the engine with the hand crank periodically over a few days it came
free.
One Year Later: The Manana Man swings into action,..
The Oil Strainer:
I pump out the MMO and change the oil 3 times, cranking the engine a
few secs in between. The first 2 changes were indescribable but I
finally have something that looks like oil. I used automotive Chevron
10-30 for the rinses, using a 12v electric pump with a hose attached
to a pipe at the back of the crankcase, port side to suck out the oil.
I find out the Yanmar has no oil filter, but uses an oil screen.
Q: Is this behind the triangular plate with a T-handle to the left of
the crankshaft pulley as you are facing the forward end of the engine?
This is the only thing to filter the oil? I removed and cleaned it
with diesel fuel and drooled engine oil through it to wash out the
diesel, made sure the port was lined up to the strainer inlet and
reassembled it. Is there another strainer somewhere? I can't see how
this would do much.
A: - My old Yanmar book has gone missing and I don’t recall.

Q: Is Delo400 oil alright for a simple old one cylinder engine or
should I be using a C rated oil or a specific designer Yanmar oil? I
ask because I worked for someone who used Delo400 in an entire fleet
of diesel trucks and equipment and can't remember an oil related
failure. (they were mostly alcohol related).
A:- Delo 400 is fine, but so to will any other oil rated CD-E-F-G....
This will be almost any good oil available but I would good with a multivis
like a 10w40.

Q: Are there engine Zincs to replace? Can someone describe where they
are on a YSB12?
A:- When I find the book. . .

The Seawater Cooling Pump:
I found the water pump was a giant clod of green goo so I cleaned it
up and replaced the impeller and washers from an overpriced kit. As
this boat is on the hard I ran a garden hose to the pump inlet and
turned it on to a slow stream. There were no leaks before the engine
started but when it was cranking it showed a small, steady leak from
the lower slot where the slinger gets popped in. While running, water
was running freely out the slinger hole.
Q: Is this typical of a garden hose fed arrangement or does it sound
more like a bad rebuild? It doesn't look like much water was coming
out of the exhaust but was kind of hard to tell. I remember it took a
bit of violence to disassemble the pump and the reassembly did not go
smoothly either.
A:- If I understand your slinger description right, you are talking about the
bleed hole between the pump seal and the bearing. The purpose of that slot is
to let the water out before it goes into the bearing. It sounds to me like the
pump seal might be gone (probably eaten by the green blob) or if you fed the
hose right into the pump, you may have blow it out. The best bet is to put the
suction hose into a bucket and use the hose to keep the bucket level above the
suction hose.

The Prop:
After it was running I tried the throttle and the engine revs up and
down and goes into neutral, forward and reverse. Before I ran it the
prop would rotate very stiffly by hand. Now it turns easily. I noticed
a ring of moisture on the outboard side of the prop where the nut
holds it on.
A:- Good Luck there. I can't imagine where that came from.

Q: This means there's a leak from the bilge, right? I ran the hose in
there and filled it over the box where it goes through the keel before
I started the engine. Is this the way it's supposed to work? Passing
water? (only from the outside in).
A:- The fill the bilge trick was almost good, but you should have let the shaft
packing off first so more water got into the gland to lubricate both it and the
stern (cutlass - water lubricated rubber) bearing. The packing gland is
probably dry enough to leak at this time, but turning the shaft in a dry bearing
is not good.

The Actual Running:
After opening the tank gate it took ages for fuel to fill the CAV
strainer and the electric fuel pump and the secondary filter. I bled
air at each union. Shouldn't this just rush through? I checked my new
gate, vent and clear line gauge at the tank and everything looks
alright.
I hooked up a battery charger and one 12v battery and cranked in 25
sec intervals for about 5 minutes. I got one pop and then sprayed 1/2
second of WD40 into the air intake, which seems to be just a naked
horn with no filter. After about 5 more minutes of shuddering and
gasping it ran raggedly with just a tiny squirt to keep it going and
finally ran on it's own. The was some blue/white smoke from the back
of the boat but not as much as I thought there would be. Also, there
was some smoke from the air intake which hung about in the cabin.
(engine cover off) Is this normal?
A:- If the fuel system was dry for a long time, nothing here is a great
surprise, but in the future there are a few things you could do here to save
yourself a lot of grief.

Q: How do you shut it off? Turning the key doesn't do it. I finally
had to turn of the fuel tank and it still ran on and on. I was
concerned it wasn't getting enough cooling water so I put a rag up to
the air intake. This seemed a rough expedient but it did strangle it
finally.
A:- There is not electric component required to run this engine. The key
enables the starter motor circuit, powers up the instruments (temperature and
oil pressure and runs the hour meter). Shutting the fuel off at the tank may
require that the engine fuel system be re-bleed before it will start and run
again. (Get a book and learn about that.) The shut off for all but the newest
diesel engines is a mechanical fuel delivery shut down that is cpart of the fuel
injection control. This is typically a pull cable affair that is usually handy
to the engine controls (it is not a choke).

The Alternator:
While running I have battery voltage at the alternator output but then
I noticed the panel light had been disconnected. It needs this to
excite the charger, right?
A:- This is machine specific. There are many 1 wire alternators out there.
There will be battery voltage at the terminal if there is power to the engine
circuit (there is a battery on board and the master switch is on).

The Fuel Pump:
When I turn the key on it ticks like a high powered English sports car
would but unlike a Lucas pump it doesn't pressurize and then turn off
and on as needed, it seems to just keep ticking. Is this normal?
A:- Yes (I’d Love to just stop here)
The Lucas pumps would stop when the system was pressurized to the float valves
(you don’t have any of those), but since your engine has a fuel bleed/return to
prevent the fuel system from getting air bound some fuel is always returning to
the tank (so the pump keeps running).

That's it, that's all. I'd appreciate any advice anyone can offer the
DIYer. Thanks and smooth sailing.

If I didn't clear up most of your questions, try again.

Matt Colie
Lifelong Waterman, Licensed Mariner and Perpetual Sailor