Yanmar SB12 Using Oil

[Homer Shannon]

Yea, I was able to locate a photo of the part on line and that's exactly what it looks like. I was able to loosen the 17mm lock nut but the pipe did not want to thread out easily and I didn't want to take a chance on breaking it off and creating an impossible drill-it-out situation. I tightened the locknut and went back to trying with the big torque wrench.

With a drop light, a mirror and lots of cussing I was finally able to get both rod bolts tightened to 40lbs. It took over an hour just to tighten two bolts! I'll save the joy of installing the oil pan for tomorrow.

I ordered the wrong head gasket - apparently copied the number for the SB8 - so I'm going to be held up on the top end work for a while. The right one is back ordered for about ten days. From here, though, it's all pretty easy - just put stuff back where it belongs. Everything is looking surprisingly good. The rod bearings were in great shape - I'm going to keep them, just in case I ever need them. The zink does not need replacing yet. I checked the thermostat and it is working fine. I think this old motor has more life in it at this point than I do.

[Wotname]

For future reference, 1/4" drive sockets and extensions plus adapters to 3/8" and 1/2" work wonders in tight or confirmed spaces.

However your perseverance also worked .

Shame about the head gasket, I'm sure you are dying to get it running again.

[Compass790]

Originally Posted by Homer Shannon

I probably have a tube of Form A Gasket or other material laying around from my (ancient) days messing around with dirt bikes. I suppose that is an option.

With the silicon technique - you apply the silicon and let it cure before using? That might work as the pan is tricky to put into place and any liquidy material would likely get smudged off before the pan was properly positioned.

While we are discussing this, I noted that the oil pan holds about two quarts of fluid (I actually measured it) and the motor calls for 3.5 quarts of oil. I was assuming that this means that oil pan gasket is always holding back a dept of fluid until I stumbled across a specification for the SB12 (no idea what document this was, now) that listed: Oil Capacity 3.5 liters and "effective capacity" (or something like that) 2.1 liters. Would this indicate that 2.1 liters are in the sump and the rest is in the crankshaft, oil filter gallery, etc.? If so, the gasket would be at the top of the sitting oil, but not below the oil "waterline", which would make sense.

I'm going to check the dipstick while I have this thing apart and see where the full range is relative to where the gasket is. It does not seem like a good idea to have a sump that is always flooded above the gasket. If that is the case, I certainly need a very good seal.

FYI: found out that effective capacity is the difference in capacity between the maximum & minimum marks on your engine oil dipstick. This is from a 3gm30 manual so our asumption wasn't correct. Still glad I learnt something new.

[Homer Shannon]

After weeks of delay due to a back ordered head gasket, I’m finally getting this engine back together. I’ve got the head reassembled and I’ve run into two items that I think are worth discussion before I go further.

The first issue is straight forward. The rocker arms move laterally their shaft about 5mm. I’ve never noticed this before (never had the valve cover off!) but don’t see where I’ve made any errors. The rods are properly seated and the valve stem caps are in position. The valve train seems to operate correctly. Is this lateral movement normal?

The second issue is a bit more complicated and is going to involve a fuel modification. The fuel bowl assembly on this motor has always been a problem. Because it built of white metal, you cannot torque the banjo bolts sufficiently to properly crush the copper washers without fear of stripping the threads of the assembly. Today, when I went to reassemble the fuel lines, with minimum torque on the banjo bolt, the thread on the fuel return line stripped.

I would love to discard this device. It always leaks and it leaks onto the starboard forward motor mount, which does not do the rubber of the mount any good. It has also been the source of air leaks and inconvenient motor failures. This is my plan for replacing it. I would like the input of the members on this this before I proceed.

The fuel bowl has three connections: input from the lift pump, output to the high pressure pump and a return from the fuel injector. There is also a vent screw (which is also a source of leaks). I am proposing to cut off the fittings on the lift pump line and the line to the high pressure pump and connect them together with an inline fuel filter (I have a bulkhead filter as well). I will then take a small rubber line from the injector fuel return line (this line is metal and measures 3/16 OD) and run it to the fuel tank. I can connect this line to the fuel tank by means of a T fitting in the vent line, which runs vertically about 18” after exiting the tank.

If I understand how this system works, this change would simplify bleeding the fuel system as I won’t have to ever bleed the return fuel side. I know I could replace the lift pump with an electric pump, and I may consider that, but for now I’ll use the lift pump – it was new last summer. By eliminating the three soft banjo connections and replacing them with hose clamps, I think I’ll be able to stop all the leaking. Does anyone know the ID of the large fuel lines? I will need this dimension to order a fuel filter and would rather not cut the fuel lines until I've attempted to start the motor (yes, I know it's going to leak).

What do you think?

[Compass790]

Yes Homer the lateral movement in rocker is perfectly normal. The rocker cover limits stop them from coming off combined with the seating of the pushrods.
As to the fuel filter thats pretty much the same as I have done with the ysm8 & it works fine. I wanted to put a 25 micron primary filter & a 5 micron secondary in the circuit & escape having to buy Yanmars gold plated filters. I added a priming bulb in the circuit to make it easy to bleed as the priming lever on the lift pump never seemed to work any good. I didn't want to replace mechanical lift pump with electrical as it's lasted for 37 yrs AFAIK but I do carry a spare 12v fuel pump on board

[Homer Shannon]

Compass, that's what I wanted to hear! I, too, have a priming bulb, so I don't really see the need for an electric pump. The only tricky part is finding an adapter to allow me to connect the 3/16" return line to the 5/8" tank vent line. I've found a 5/8" tee with a 5/16" side barb and I think with 1/4" hose I can probably make that work - there's no pressure in the return or vent line.

Do you happen to know the ID of the large lines that run from the lift pump to the fuel bowl and from the fuel bowl to the high pressure pump? I believe these are 1/4" ID (or 6mm), but I'd rather know before I start ordering parts. I've found a pretty nice filter that will fit 6 to 8mm lines. My only concern is that the manufacturer does not list the filtration size. I believe the fuel bowl filter is 5 micron, which is finer than most of these inline filters.

What filter did you wind up installing. The WIX 33001 looks good but it's rated 12 micron. I don't see any rated 5 micron.

[Compass790]

I THINK the lines are 6mm but my memory is not to be relied on & cant locate old filter bowl at present. Will get back to you or maybe Wotname can tell you. I have a CAV type bulkhead mount type filter for primary it's a Fram C1191A & it's actually 10 micron. ( see what i mean about memory lol) My second filter is a spin on Baldwin BF988 5 micron that goes on a remote oil filter mount
AFAIK the Yanmar filter is 10 micron so i guess that's all thats needed but I dont mind having 2 filters as injection pumps are expensive, well any part called yanmar is expensive.
boy i bet you dying to get it fired up!

[Homer Shannon]

Well, if the Yanmar filter is 10 micron, I don't see any harm using a 12 micron filter. I'll get the parts I need on order tonight so I can wrap this thing up before we have any serious snow. Even if I can't get the return line installed to the fuel tank, I can just run the return to a jug while I try and start the engine.

This actually does not look very difficult to do. Given the hassles the onboard fuel filter has caused over the years, I don't know why I didn't do this decades ago. I guess the answer is that I just didn't know about an alternative.

[Compass790]

Whoops told ya my memory was not to be relied on! Just found Yanmar filter bowl & banjo fittings are 8mm. Will try & post pics of it but in nxt post.

[Compass790]

Hope photo is there. I'm no 'puter whizz

[Wotname]

FWIW, the in/out lines on the GM series fuel filters are 8mm and the fuel filters look the same as the SB & Y series filters. Also the bleed screw on these filters now have a plastic sealing washer rather than a copper crush washer and it only needs to be lightly nipped up to seal.

[Homer Shannon]

I woke up thinking about this, so once it was light I went out and removed one of the hoses and measured it. A 1/4" hose would work, but a 5/16 is much better, so that's what I'll go with. I can also order an 8mm banjo with a fuel line barb to replace the one on the injector that has a steel pipe.

[Compass790]

Glad you sorted it, let us know how she goes on startup. Can't be much fun workn on engine in that cold weather.

[Homer Shannon]

It's not too bad inside the boat; just a little dark because I've got a cover on it back to the cockpit. The tools are pretty cold so I use gloves when I can. I think when I fire it up I'll just see if it kicks then shut it down. Not much point in trying to get the cooling system hooked up to a hose and all It's bone dry right now; I don't have any worries about freezing.

[Compass790]

Oh darn it, we wont hear if you've solved the problem until nxt summer then. But I dont blame you. You'd have to drag me in chains to a boat when it's that cold so good onya for getn that far