Yanmar SVE8 v SB8 Specifications

[mm]

I have a Yanmar SB8 in my C28 which is smoking rather badly on higher revs.  The engine still starts easily and runs ok apart from this problem.  I have a diesel mechanic friend ready to help with some work on rings/head etc to hopefully address the smoke issue.

Because of the cost of hard stand or marina berth time I'm anxious to be as prepared as possible for the work.

I have found workshop manual for the SVE8 (1974-76), the predecessor to the SB8 (1976-80) but cannot find a workshop manual for the SB8 anywhere.  I even spent quite a few dollars with a US company whose website and email correspondence stated that the advertised manual was for the SB8, only to have it arrive with no mention of SB8 anywhere in the document!

The engine has a Lacey Marine sticker on it and Ian kindly spent quite a bit of time trying to track down some history on the engine and any SB8 documentation without any luck unfortunately. Thank you Ian!

Any guidance would be very much appreciated

Michael

[michael]

Try Minards  "www.minardsdiesel.com"  they have a dearth of information on Yanmar. Have you checked the exhaust riser for blockage? My old YSE8 slowly got more and more Smokey and loss of power, and I found the riser was choked with a build up of carbon. Just a thought.

Cheers

Michael

[Tardis29]

Hi Michael,

Do you have any oil leaking from the crankcase breather tube under high revs? This a small metal tube at the bottom right of the engine as you look at it. Oil being blown out of this tube can suggest worn piston rings resulting in excessive blow-by gasses in your crankcase. I was having similar issues with exhaust smoke and oil blowing out of this breather tube and the cause was worn piston rings. I had a complete rebuild by Lacey's about ten years ago and it's been running very well ever since. No smoke and easy starting.

I seem to recall that the only workshop manuals available are for the Yanmar YSE and YSM models, but nothing of any great value for the YSB8/12. However all of these models are similar enough that the YSE and YSM manuals are still relevant.

I have PDF copies of;
parts list for YSM8/12 (with diagrams)
parts list for YSE8/12 (with diagrams)
service manual for YSE8/12
service manual for YSM8/12
operation manual for YSB8/12 (basic)
service manual for 1GM10 / 2GM20 / 3GM30 / 3HM35

I'm reluctant to post links to these manuals online owing to possible copyright issues but let me know if you would like a copy of anything that I have and I'll forward an email with links later tonight.

Regards,
Paul

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[mm]

Michael - I have tried Minards and whilst very friendly and supportive they only had a photocopy of the SVE8 manual.  The exhaust system was in poor shape and I have had it replaced by the guys at Marmong Marina.  Whilst it improved power levels it hasn't addressed the smoke issue.

Paul - I will check the breather tube this weekend, I suspect you are right.  Thank you for the kind offer of assistance with the manuals.  I also appreciate and respect your concern about copyright.

Thanks to you both for taking the time to help.  Very much appreciated.

Michael

[Graeme Lock]

Hi Michael;

Pardon the dumb question, but are you sure it isn't growth on your prop causing overloading at higher revs? This would show up also as an inability to rev as high as it formerly did. Apologies if you've already checked, but it might save you a heap of dollars.

Cheers, Graeme

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[Maeling]

Paul within two days I'll mail you and put mm in direct touch after I figure out who he is. For MM what colour is the smoke, black blue or white?  For us all, It's probably that time of year before it gets too cold, I must take a dip after the water clears to check mine

Geoff Raebel

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[mm]

Sensible question re the prop but all good there.  I went for a swim a couple of weeks ago to clean up some growth around the waterline and had a good look at the prop.

Smoke is definitely black.  Also some oil with it when cold or pushed really hard.

Michael

On Tuesday, March 28, 2017 at 1:31:07 PM UTC+11, mm wrote:

[Maeling]

Smoke is black indicates she is too rich because the governor is sensing the load and moving the rack to push in more fuel but she can't use it and get to the revs.  This happens where a prop is too coarse and while the engine can turn it, the engine is over loaded and can't get to the revs.  Now what was the question?  Do you have a tacho or can you borrow a portable one?

Geoff Raebel

[mm]

Thank you for that information Geoff.  This is my first boat and whilst I've got some reasonable general 'handyman' skills I'm learning 'on the job'.  I will discuss this with my friend before we do anything too drastic.  As I mentioned in my first post, the engine starts very reliably and runs well but the smoke is definitely a concern.  You have given us a lead to follow that I hadn't considered.  Thank you.

Michael

[Graeme Lock]

Michael;'

Another question - has this been the case for a long time, or is it a new phenomenon that suddenly started?

If it's been that way forever and won't rev up near rated maximum, over-propping is a prime suspect.

If you don't have a tacho, it may be possible to measure rpm with a multimeter that can measure the frequency of a pulse train. Many Yanmars use an inductive pickup which reacts to the teeth on the flywheel ring gear. If yours has this and you can find out the number of ring gear teeth, the arithmetic to convert pulse frequency to rpm is pretty simple. I have done this on the 2GM to see how accurate the tacho is.

Cheers, Graeme

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[mm]

Hi Graeme, the smoke is not a recent phenomenon.  I have a sense it has got worse however, particularly when pushed hard, but that may be an old man's perception playing tricks.  I don't have a tacho on the old SB8 but do have a mulitmeter.  Thank you for the suggestion.

Michael

compass-y...@googlegroups.com

[michael]

Hi Michael, further to the tacho idea. I purchased a digital laser tacho from "eBay" (Digital Laser Photo Tachometer) for very little money as I wanted to check the validity of my engine tacho. Works well and is handy to have in the tool kit. If the smoke is not a new, or a worsening thing, then I would look at the prop specifications, usually stamped on the prop hub. Do it soon while the water is still not too cold :-)

Cheers

Michael

Pisces, I33

[mm]

Hi Michael

Thank you for the information on the laser tacho, I will definitely follow that up.  When the rain eases off I'll also get out to the boat and check out the prop details as you suggest.

It's interesting that I still can't seem to find a workshop manual for the SB8, the earlier comment that one may not have been produced is looking very likely to be true.

Thanks to everyone who's taken the time to offer their assistance.

Michael
C28 Bittersweet II
Lake Macquarie NSW