View Full Version : Blue smoke, black smoke, Nissan SD-23.

07-20-2012, 05:18 PM
My Nissan SD-23 marine engine has blue smoke at idle but clean at faster speed.
Clean at full speed in neutral, but under load at full speed, lots of black smoke.
What is my problem with two different colors of smoke at different speeds and loads?

Sailing Nevada lake Mead.

07-21-2012, 01:06 AM
Hi Denny,
Blue smoke at idle is oil burning, which would explain your low compressions.
The black smoke is caused by over fueling or lack of air.
Either a blocked air cleaner or could be injectors.
Also, but rarely the injection pump setting.

07-21-2012, 10:27 AM
Thanks again Mike. Having this boat and motor for about a month I am reluctant to dig into the engine to deep until I am educated more. I will check the air cleaner.
Sailing Nevada Lake Mead

08-21-2012, 10:25 AM
I have the cylinder head off of my 1972 SD 33, and got a gasket set (from Tiffin Parts in Ohio) that is for a 1980 and newer, even though I specified the earlier engine.
It came with a lot (10) of rubber coated rings that look like they are the same size as the small copper gaskets for the injector tips, and some larger ones that look the same size as the upper copper compression seal on the injectors....the kit also has 6 small copper rings for the injector tip, but only two of the larger copper rings...it has a couple of some medium sized rubber rings too...
I have a free copy of the service manual from the internet missing three pages (M 15-18) and tried to buy a copy but it is missing those pages too. The manual says "don't forget to install the rubber seals" in the head gasket...
I have placed two of the large rubber rings in the head gasket at the rear end where they fit over what seems to be oil passages, and two of the medium ones on two passages forward of No 5 cylinder....there is another hole at the rear end of the gasket, that has a "stepped" end in the block, and there is one copper "compression' type ring that seems to fit there, but I am not sure about what is supposed to go there...So basically, I am missing a drawing of the head gasket that shows where the sealing rings go, and a list of the parts that are required...the 1980 gasket set has smaller valve guide seals too, but I cut the valve guides down and used a better type, so that seems to be ok...but it is frustrating not being sure about why there are so many of the rubber coated rings, and not knowing where they go...there are holes in the gasket that are the size of the small rings, but they are "blank" against the block and head...no passages in either, at those holes...should I put the rings there? are these a new type of injector seal? I took the head off because there was a lot of white smoke that smelled like unburnt fuel, but seemed to be water vapor, but the head gasket did not look "blown"...so I had it serviced, and now have this problem with the gasket set...any guidance would be appreciated.
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