Yanmar SB12 Using Oil

[Compass790]

What Wotname says. My GUESS is T is top ring,Tp 2nd,T3 3rd but I could be wrong. You could try calling Toad & check. I'll try & post a pic from YSM12 manual as, interestingly, taper on 2nd ring is different than YSE 8 as posted by Wottie. However this is my 3rd & last go to post a pic as all I've managed to do so far is make the post disappear

[Compass790]

Forgot to say, as you pointed out, ring design better so thats hopeful for an improvement in your oil consumption .Be interesting to hear if the rings were your smoking gun.

[Homer Shannon]

Wotname, thanks for the input, but that diagram shows rings that are neither like the ones that came our nor like the ones that I have to put in. I'm kind of guessing that the sloped ring is the third one and the slope goes down. Perhaps the silvery one is chrome and will shine up with use. That would be the top on.

No work until Tuesday. Perhaps by then I can get a firm answer. I to have a message in to TOAD.

[Wotname]

Compass790 got me interested after posting the differences in the rings between the YSE and YSM which are essentially very similar engines of the same vintage (and similar to the OP's SB). How much difference is there in later (but still old) Yanmar small marine engines.
So I looked at the QM manual and the GM / HM manuals all of which succeeded the YSE /YSB/YSM/SB.

All top rings were chromed faced on the surface facing the liner and all had D or barrelled face; the HM also had tin plating over the chrome.

The second ring was always tapered (with the sharp edge towards the crank).
The third ring was also tapered in the QM. The GM / HM does not have a third compression ring.

The taper was slight (0.5 to 1.5 degrees) and reading between the lines from the GM / HM manual, this taper would wear away over prolonged use.

This might explain why the OP's original rings may no longer appear to be tapered.

My take away is the new rings should be installed as follows.

The silver one marked T at the top. The T meaning top and silver colour is either dull chrome or chrome that has been tinned over (HM style).

The one marked Tp is next (#2) with the Tp meaning tapered.

The one marked Tp3 after that (i.e. #3) with the Tp3 meaning tapered in the number three position.

This concurs with Compass790's guess ().

All manuals stated the marks should face the head. I found the marks to be very tiny and hard to read but maybe it is just my eyes

It will be interesting to hear what TOAD says!

[Homer Shannon]

Thanks everyone. I think we have the order worked out. It has occurred to me that the rings may have been in order and facing the right way in the box. Of course, I did not open the box and check that. Doh!

I've noticed that the oil ring does not have any type of an expander ring, which the YSE manual calls for and a video I found (for a different Yanmar model) discusses. Since the parts listing does not show one for the SB12 and the ring set does not include one, I'm going to assume that this is the way it is supposed to be installed. Is there any reasonable chance that the expander ring has its own part number that is not part of the ring set?

[Compass790]

Originally Posted by Homer Shannon

Thanks everyone. I think we have the order worked out. It has occurred to me that the rings may have been in order and facing the right way in the box. Of course, I did not open the box and check that. Doh!

I've noticed that the oil ring does not have any type of an expander ring, which the YSE manual calls for and a video I found (for a different Yanmar model) discusses. Since the parts listing does not show one for the SB12 and the ring set does not include one, I'm going to assume that this is the way it is supposed to be installed. Is there any reasonable chance that the expander ring has its own part number that is not part of the ring set?

The bit about the rings coming in the order they were meant to be installed was in one of my posts to you that disappeared but I forgot to include it in the post that made it. The Yanmar ring sets I sell made by Riken who make rings for Honda dont have the expander ring under the oil ring either but they work. No chance it's a seperate part no.NPR rings still have them.
I suspect its just another design change so don't sweat it. Just remember lettering to the top.

[Wotname]

Originally Posted by Compass790

.........
I suspect its just another design change so don't sweat it. Just remember lettering to the top.

I concur and I've given up trying to understand the methodology behind oil ring design. It seems everyone is different, they keep changing and they all work (I guess).

[Homer Shannon]

Thanks guys. You are an invaluable resource! I'm still hoping I can start reassembly on Tuesday. Unfortunately I discovered today that the oil pan gasket I ordered is not the right part. The number seems to be correct but the part is way too small and only has six bolt holes - the oil pan has eight. I've got a message into Toad. Hopefully it is not something that is going to take a long time to get.

[Compass790]

Originally Posted by Homer Shannon

Thanks guys. You are an invaluable resource! I'm still hoping I can start reassembly on Tuesday. Unfortunately I discovered today that the oil pan gasket I ordered is not the right part. The number seems to be correct but the part is way too small and only has six bolt holes - the oil pan has eight. I've got a message into Toad. Hopefully it is not something that is going to take a long time to get.

You can easily substitute with silicone for the pan gasket if it's too much of a PITA to get another gasket. I just smear an even layer on one face & let it go off overnite & then bolt up.You can reuse the old gasket that way or have no gasket at all, just the silicone. Either way works

[Wotname]

Soon we will be having you making your own gaskets

Opps, Compass beat me!

[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.

[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.

I'm not quite sure about effective capacity but i assumed the same as you. Hopefully someone who knows will chime in. We dont have any gaskets on our engine/gearbox except for a head gasket. All the other joints are either silicone or Loctite 515 master gasket or 518 flange sealant. YSM has vertically split crankcase so joint is below oil level. No leaks.
Yes I let the silicone go off so you have a thick layer to compress when tightening bolts.If you put on uncured most squeezes out. You don't have to tighten real hard but i use Loctite 242 ( or other threadlocker) on bolts to make sure they dont vibrate loose. I would do that on bolts even if I had a new gasket

[Compass790]

Originally Posted by Compass790

The bit about the rings coming in the order they were meant to be installed was in one of my posts to you that disappeared but I forgot to include it in the post that made it. The Yanmar ring sets I sell made by Riken who make rings for Honda dont have the expander ring under the oil ring either but they work. No chance it's a seperate part no.NPR rings still have them.
I suspect its just another design change so don't sweat it. Just remember lettering to the top.

CORRECTION: I just checked NPR rings for Yanmar & the oil control ring no longer has the spring expander either. I think they did a few years ago. The thought occurred to me that maybe it's possible that your existing rings may have been installed upside down?? Unlikely but possible. Too much sake the nite before on the assembly line? Oil scraper ring looks like it could go either way in current design of NPR & Riken tho. But I think the 3rd compression ring can be cut to assist with oil scraping. They are on the Rikens. Not sure how yr yanmar rings are cut although they are likely made by NPR.

[Homer Shannon]

I got the piston in this morning but I'm having a difficulty torquing the rod bolts.

I can't go in from the side because there is a bulkhead too close to allow use of a reasonable sized torque wrench. If I go if from the bottom with 4" extension on a 1/2 wrench, I'm too low and I'm hitting fixed boat parts like through hulls and flooring. If I go to a 2" extension I hit the oil pickup/ screen.

I think the best route will be to remove the oil pickup and use the 2" extension. This thing looks like it has a 17mm hex head and just unscrews, but there is no mention of how it is fastened in the workshop manual. Before I go in and bust or damage a critical part, can anyone confirm how this thing comes off?

[Compass790]

Originally Posted by Homer Shannon

I got the piston in this morning but I'm having a difficulty torquing the rod bolts.

I can't go in from the side because there is a bulkhead too close to allow use of a reasonable sized torque wrench. If I go if from the bottom with 4" extension on a 1/2 wrench, I'm too low and I'm hitting fixed boat parts like through hulls and flooring. If I go to a 2" extension I hit the oil pickup/ screen.

I think the best route will be to remove the oil pickup and use the 2" extension. This thing looks like it has a 17mm hex head and just unscrews, but there is no mention of how it is fastened in the workshop manual. Before I go in and bust or damage a critical part, can anyone confirm how this thing comes off?

Can only tell you our ysm8 the pickup pipe unscrews & the nut on it is there as a locknut but dont know if SB12 is the same. Can't see it hurting to try & unscrew the 17mm nut tho.