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YANMAR SB12
RUNNING THE ENGINE

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This page was last updated on 10 July 2001

After much preparation, the time came a few weeks before launch to test-run the engine.  I had a few final things to do before attempting a startup.  First, I checked all the fuel connections, and replaced the secondary fuel filter with a new element.  I checked the engine mounts to ensure their tightness, and removed the suction side of the intake hose from the raw water pump, replacing it with a length of hose long enough to run into a 5 gallon bucket of water. I ran a garden hose with a valve at the end to the bucket so I could add more water as necessary. Then, I added 5 gallons of diesel fuel to the fuel tank, and checked all connections again.  Using the outboard primer bulb I installed in the fuel system, I primed the fuel system and bled the lines, at least as much as possible at that point.  I connected my starter battery to the cables that I installed over the winter--just a ground and the starter feed for now.  As I tried a test-start just to check the electrical connections, I realized that I had neglected to run the power feed to the gauge panel--duh.  I connected the ground wire to the negative distribution buss, and the positive directly to the battery for now.  Success!  The starter cranked right over.

After a final check of everything, I prepared for a real test run.  With the throttle advanced, the engine started almost immediately.  At first, I wasn't sure it was drawing in cooling water, so I shut down to check everything.  All OK, so I restarted the engine, and after a moment it settled down to a reasonable roar.  The engine ran fine for a few minutes before beginning to die, apparently signifying air in the fuel system--a common issue, and not surprising considering that the fuel system was entirely new, had never been primed, and the engine hadn't been run for well over a year.

Several bleeds of various areas did not allow the engine to start, and I have found significant air in the secondary filter housing, which filter I changed just before the initial start.  I think this is the problem, and will continue bleeding until the beast starts again.  All it takes is a little air to cause this problem, so I am confident that there is nothing more significant wrong.

After more attempts at bleeding, there were still no positive results. For those of you who may be interested in the diagnostic process, I have included the drawing from my shop manual.  It shows an exploded view of the high pressure injection pump.  

After installing the new pump, and rebleeding the whole system again, still no luck.  Smitty admits to being baffled--he said he's never been stumped by a one-lunger before.  He took apart the injection pump, and all parts seemed to be working properly.  Then, he took the pump into a local shop that specialized in diesel fuel injection, and had the pump tested--OK.  His latest thinking is that maybe there's something fishy going on with the governor/throttle system.  That's where he will focus his attention when he returns today (Saturday, 5/12).

UPDATE 5/14:  No luck yet. After reassembling the pump, Smitty noted while I was cranking the engine that the gasket beneath was seeping fuel--and thus air.  He had been afraid of the condition of the gasket all along, but hoped to eek it out for testing purposes.  Not!  That basically shut us down while we wait for parts--I ordered parts to rebuild the existing injection pump, then also went ahead and ordered an entire new assembly.  Of course, nearly all the parts we ordered aren't available overnight as we had hoped--instead, they will ship after a couple days, so they won't arrive here at best until Thursday the 17th--launching day!  We're going to go ahead with launching no matter what, and deal with the engine afterwards.  Work can be done just as easily with the boat in the water.

UPDATE 5/26:  The engine runs!  Finally, after frustrating delays waiting for parts, we received the new fuel injection pump and installed it.  The engine started almost immediately.  When comparing the two pumps--the old and the new--it was obvious that the old was bad--the piston was all loose and sloppy, while the new one was clean and tight.  The old pump will be rebuilt with new parts for a spare--seems like it might be good to have a large inventory of spare parts for this engine, particularly the inexpensive ones that we can afford to stock.  Nothing would be more frustrating than more of these ordering delays if we really need a part down the road--or worse, complete unavailability of a certain part!

The engine sounds good and is smoother and quieter than I expected...but it does vibrate a lot, and engine room insulation will be a priority for those long days motoring if there's no wind.  Soundproofing material is already on hand--I ordered it months ago, but never had a chance to get it installed.  I hope to install it within the next few weeks, prior to a planned two-week cruise in July.

We have a little fine tuning to do with the throttle and governor system, but other than that, we're in business.  I even got the engine gearshift hooked up, finally!  (Details on that here)

UPDATE 6/1:  After a marathon, four-hour session, Smitty and I seem to have the throttle action and governor adjusted to a place we can live with.  The problem before was that there was a lot of throttle creep--that is, when you advanced the lever, the springs on the governor assembly would pull it annoyingly back.  Also, the idle speed was too low when the throttle lever was pulled all the way back--in fact, the engine would shut down.  I wanted to be sure that dead idle speed would be high enough to allow shifting without a problem, and we will shut the engine down with a previously installed cable attached to the decompression lever.

The fuel adjustment and governor assembly is like nothing Smitty (or I) had ever seen.  I marveled at his patience as he fussed with the thing--there is literally about 1/16" difference between full fuel and no fuel on the needle valve at the fuel injection pump.  This makes adjustment extremely difficult, if not impossible.  However, during those four hours, Smitty made good progress with the adjustment, and eventually we got things adjusted out so that now we can make minor adjustments with the idle speed screw, as intended--before, when the engine was at a suitable idle speed, there was about a 1" gap to the idle screw when it was maxed out.  I don't know how he didn't throw something overboard in frustration during this process--but I'll bet he wanted to!

Things seem to be adjusted properly at the moment.  The next step is a test with the engine under load--that is, in use.  We couldn't do it after the adjusting session because it was nearly 9PM when all was said and done, and the launch service ends at 9.  Plus, it was dark out, or nearly so.  I will take the boat out soon and check the engine's operation when the gear is clutched in and report back.

FIRST ENGINE USE  6/1/01  Well, I took the boat off the mooring under her own power for the first time.  There's still some fine tuning to do.  The throttle creep is a real problem--the throttle just won't stay at the proper setting where I want it.  I think we'll add a return spring to hold things in place.  I don't have gauges hooked up yet, so I don't know what RPM I was turning.  However, I was able to achieve over 5.5 knots, with room to spare before WOT.  At just over idle speed--the spot where the throttle lever always seems to end up--I got around 3-3.5 knots, according to my knotmeter and GPS.  Perfectly acceptable.

The engine smokes a lot.  I hope this is going to stop eventually--it's embarrassing, and stinky.  Also, there is apparently a lot of combustible material on the engine block itself, as the engine room gets smoky.  There's probably plenty of diesel residue left over from all that bleeding, which made a real mess of things.  It's been cleaned up, of course, but the residue is there to slowly smolder.  Hopefully, that will stop, too--a cabin full of smoke is no treat.

After a short run outside the anchorage, I returned to my mooring.  I went below to open the engine room and look at things (with the engine running), and, much to my surprise, there was water running everywhere, particularly on top of my new starter.  Cool.  I shut down, and looked for the source.  At first, it looked like it was coming from the engine exhaust hose somewhere, but it was not; it was only running down the hose because it was close by.  The leak (not a leak so much as a true gushing) was coming from a fitting on the port side of the engine, just above the starter. (That's it in the photo, just above the belt in the foreground...)  After consulting my parts manual, I determined that this is a drain fitting, and the fitting had opened because of the vibration of the engine.  There's a nut on the end that I tightened to stop the flow.  There is supposed to be a drain hose attached to the fitting, and I guess it's used to help drain the engine for winterizing.  It was only indicated by name on one page of my parts manual, so it took me some time to actually figure out what it really was.

Don't ever let anyone tell you that commissioning a new boat (or one that is, for all intents and purposes, new, even if it's old...) is easy--there are so many things to overlook, and therefore to go wrong.  We are really closing in on it, however--for now, we'll take it slow and easy, and get everything worked out in short order.

The engine doesn't pump that much water, either.  This makes for a noisy exhaust note, and it's a little disconcerting.  I'd be happier to see more water coming out the exhaust.  I have to check into this--I know the pump works.  Perhaps the need of the engine is just so low, that it takes a while to fill up the waterlift chamber--which has to happen before back pressure ejects the water out the transom.  Definitely still a few things to check out...but I think it will all be OK in the end.

UPDATE 6/8/01  So, the fun continues. The white smoke and lack or exhaust water are two major concerns.  From my own research, I determined that white smoke is generally caused by one of four things:  

  1. Cracked block or head, allowing coolant (seawater) to enter combustion chamber

  2. Blown head gasket, which would also allow coolant to enter the combustion chamber

  3. Improper combustion, caused by bad fuel, water in the fuel, or improper injection

  4. Fuel in the lubricating oil

Of the list, obviously #1 and #2 are less likely than #3 or #4.   However, I had heard from a friend with past experience that these engines tend to blow head gaskets.  So, I ordered a couple to have on hand regardless.  The cracked block syndrome is far less likely--I mean, the engine runs like a top, except for the exhaust smoke.  Smitty's guess:  fuel in the oil.  First step:  change the oil, which was on my list anyway.   The thought was that fuel had been leaking down through the mechanical side of the injection pump before the new one was installed, so it probably had diluted and contaminated the lube oil.  After changing the oil, however, there was no real change.  Also, Smitty noticed afterwards that there was pressure in the oil pan--oil sprayed out the dipstick hole when the dipstick was removed with the engine running.  There should be a slight vacuum.  No harm in trying the simplest fix first, of course, and the oil needed a changing anyway.

Next thought:  pull the injector nozzle and have it pop tested.  Removal was a fairly simple task, and the nozzle was out in a few minutes.  The next day, I ran over to a local diesel injection specialist, and for $8.00 they tested the injector for me.  Results:  excellent.  Scratch that off the list.

With the injector removed, and the top end of the engine already partially disassembled, we decided to go for it, and remove the head to replace the gasket.  The first thing Smitty did was remove the starter, so he could set the engine at top dead center and ensure that the timing was on.  This involved removing the alternator for timingmark.JPG (166964 bytes)better access, then unbolting the starter housing to expose the flywheel behind.  After lining up the timing marks, off came the bonnet--a simple matter, really.  This exposed the remaining two head bolts.  That was it for the evening, as it was nearly 9PM.

The next night we were right back at it.  In about 2 seconds, Smitty had the head off.  All in all, it seemed to be in pretty good condition.  (I forgot my camera this night, so no pictures of the disassembly--sorry!).  There were no signs of cracking, but one of the cooling passages for raw water was completely plugged up.  The gasket looked a little tough, but it was hard to tell, since it was torn apart somewhat by removing the head.  It looked like there was one area that was definitely not right, though, so that seemed to make the job worthwhile.  The valves, combustion chamber, and piston all looked to be in good condition; rotating the crankshaft a little lowered the piston (by the way, the timing marks are right on, as the piston was indeed at TDC when the head was removed), allowing us to check out the cylinder walls.  Generally OK, which was good news.

After cleaning off the old gasket from both sides--a time consuming process--the new gasket was installed, and the head reattached.  That was it for that night, as we had to order some additional gaskets in order to reassemble the exhaust system.  The thermostat looked a little suspect too, which might be accounting for the lack of cooling water out the exhaust.

UPDATE 6/17/01  After a few delays, we finally got the top end of the engine back together.  In the process, the valves were readjusted back to factory clearance, and we checked the engine timing--it was off about two degrees, so Smitty removed a little shim from beneath the fuel injection pump.  This is how injection timing of adjusted on this engine, and removing the shim changes timing by 2 degrees.  Right on!

With the exhaust system reassembled, and a new thermostat installed, we had high hopes when we cranked the engine.  There was still some smoke, but it seemed to be maybe a little less intense than before.  However, there was virtually no cooling water coming from the exhaust outlet--there really hadn't been all along through this whole process, a real concern of mine.  The good news, however, was that the engine ran like a top--smoother than before, quiet, and generally being a real trouper.

The next step was diagnosis of the cooling system.  All parts were checked, beginning with the obvious--the strainer and raw water pump--and moving upstream from there.  The pump seemed to be operating fine, and has a new impeller that I installed earlier this year.  Why wasn't there any cooling water?

After removing the exhaust silencer and thermostat housing again, Smitty finally found the likely culprit--the main cooing water passage through the silencer was blocked so badly that neither of us had even noticed it was supposed to be there, despite repeated inspections of the housing.  It was plugged solid.  It was cleaned out, and the housing reassembled.  Success!  Finally, the exhaust belched some black, nasty water, and continued purging in the expected bursts from the waterlift exhaust system.  This was good news, finally.  The exhaust note, which had sounded like we had a cherry bomb installed, was smooth and quiet.

We ran the engine for a time the next day, and the white smoke seemed to dissipate after a while.  Given the color of the exhaust water, it definitely seems that the engine has to burn through and purge some junk from within, so we can deal with a small amount of smoke.  Except for throttle creep, the engine pushed the boat successfully, and sounded great--smooth and relatively quiet.  Later, I intend to install engine room insulation, which should really shut things up.

Next:  giving the engine a good, long, hard run under load to try and burn things off and clean it out.  Click here for details of the test.

UPDATE 7/10/01  Lack of satisfaction with the engine continues.  In the weeks since replacing the head gasket, we have used the engine minimally because of excessive smoking at all speeds.  This causes embarrassment--we seem to have our own personal fog bank following us at all times.  It's obvious that the engine is in need of a real rebuild--top and bottom ends--rings at the very least.  This is not something we are interested in or inclined to do--while the engine might turn out fine afterwards, I can't see putting any more time and effort into a nearly 30-year old engine that may or may not be properly suited to the boat.  Chalk this whole experience up to lessons learned, cut losses, and move on!

The throttle creep has not yet been addressed, and is a real pain.  Obviously, this is not a factor in our decision to replace the engine, but it has made using the current engine less enjoyable.

Initially, I thought the engine would be OK to get us through the remainder of the season.  It's OK for getting on and off the mooring when necessary--we usually sail in and out anyway--and for those occasional trips to the dock for cleaning, etc.  The smoke is a major problem, however--one that we can't accept.  It's become bad enough that I don't think we can hold out for the season.  We're looking at replacement (NEW) engines now.

At the time we bought the used engine, it seemed to be the right thing to do.  That was in December 1999, only a few months after we first purchased the boat.  The boat was still a horror show, in the midst of a deck recore and interior gutting.  As a reminder, here are some photos from around that time, showing the general condition of the boat:

cockpitfwd010700.jpg (39088 bytes)        salonaft010700.jpg (41296 bytes)        coachroof.jpg (34592 bytes)        cockpitaft010700.jpg (40088 bytes)        salonfwd010700.jpg (48364 bytes)

At that stage of the game, we had barely gotten started.  Even though I had my vision for the completed boat, I had no idea how far I would take the restoration.  As time went on, I ended up deciding again and again to replace old gear and such with new.  We jumped at a seemingly decent engine when it became available, as finding a decent (ha!) used diesel is definitely not the easiest thing to do.  I figured that, when one that seemed a likely candidate came up, we had better be ready to move on it.  I definitely wanted the engine decision made earlier rather than later, since I needed it before I could begin reconstructing the interior.  Maybe, if we had waited a little longer, it would have become more apparent that something new would be more desirable.  Hindsight is 20/20, as always.  However, mistake as it has turned out to be, I stand my ground and announce that at the time, under the circumstances, purchasing the used diesel was the right thing to do.  There's no point in dwelling on the past; rather, it's time to move forward and make the boat entirely what we want her to be:  a well equipped, capable coastal cruiser with longer-term cruising aspirations.  This requires solid structure (done), comfortable accommodations (done), good sails and rigging (done), excellent systems (done), and a reliable engine capable of powering the boat through slop and current while providing alternator charging power for the ship's batteries (oops--we failed here!).  All in all, not a bad track record.

Lessons learned:

1.  Any used engine you might purchase should be torn down, inspected and/or rebuilt, unless there is reliable documentation to the effect that it has already and recently been done.

2.  If you're considering a used diesel, reconsider--unless you're a gearhead who wants the challenge and inherent project in rebuilding the engine yourself.  This could be a satisfying and fun project.  Maybe I'll even consider doing it to the SB12 if I can't find anyone to buy it.

3.  I would still prefer a diesel over even a newly rebuilt Atomic 4.

4.  Obviously, it would have been nice to have had the engine epiphany at an earlier stage in the project.  However, replacement now should be relatively simple, as I have built in good engine room access.

That's it for this page.  New engine updates will be posted here from now on.

 

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