This topic has been addressed numerous times, on numerous Forums, for probably 15 years. The bottom line appears to be that smoke, other than whit(ish), is probably bad for you and probably bad for your boat. It falls in the same category as pyrotechnics(especially on this side of the Pond where there is always a lawyer at every pond).
One option for actual smoke is to use water vapor, which is usually created by ultrasonic vibration. Again, the color comes out whit(ish).
With the exceptions of coal fired and wood fired boilers, or a diesel, a properly adjusted oil burner should not create much smoke at all and it should be grayish. If it is dark, blackish, then the chief engineer is not paying attention to his firing mix.
I have used, and am using, oil smokers and I have not found, much to my delight and in spite of my trepidation, any oily residue left on my models. I have also tried the ultrasonic water smokers. They work fine, but my preference is the oil version because the smoke does not dissipate as quickly.
Lastly, at a distance the white smoke appears to lose some of it's crispness and when the volume is adjusted it looks about right for oil fired ships.
My two cents.😊

Oil only leaves a film on the way down 🤣

Does the baby oil leave a film on the water as I sail on a drinking water lake I bought one on eBay that just uses water and makes steam like smoke but if your after the black stuff I made the effect by using a tallow candle in a box below the stack

White ish

And what colour of smoke does baby oil produce??

Johnson baby oil is mainly used at our club for smoke

We used to make purple smoke in the school lab using oxalic acid, potassium permanganate and nitric acid. lots of very dangerous purple smoke which left black dags covering the fume cabinet. Not recommended. Probably any chemical which makes black smoke might be poisonous. The old brass pump fire extinguishers were CTC which made black smoke (and phosgene) when applied to a fire (why they aren't used today) Worked ok but were nasty if breathed.

Maybe dissolved tar in oil might work😁

JB

I am also looking for a way to get a darker color smoke as Rod mentioned.

Glycerin is often a component of the fluids used in e-cigarettes. Those interested in experimenting with building smoke generators for models may be interested in the Wikipedia article, search for "construction of electronic cigarettes". Wicks, electrical elements, & their resistance & battery activation are discussed. Its a very long read, but interesting thruout.

Wicks suggested. Not mentioned, but i hav been pondering the use of fiberglass cloth as a wick, wrapped around the heating element...a low-Ohm wirewound or metal film resistor should work here.... one that wud draw say 1000 mA to 2000mA when 4.5 to 6 to 7.2 V (or even up to 12V) is applied...perhaps driven by a constant current source implemented by a LM317-series regulator configured as an adjustable constant-current supply rather than trying to monitor element temperature (or resistance) & trying to regulate the voltage.

I have tried several of the ultrasonic atomizer disks with their actuating circuit boards, with distilled water to slow contamination & extend their life, but found all of them to be unsatisfactory. Low volume of "smoke" & short life. Its also difficult to regulate the immersion depth of the disc.

I'm familiar with the model locomotive smoke units altho the outputs always looked more like steam than black smoke.

If anyone has a suggestion for grey, dark grey, or black smoke, please reply.

Search under smoker in forum, lots of experiments there.

JB

part 3d printed using a 20mm disc using water
a 4.8v battery smoke style

harbormodels.com has an assortment of different size smoke units. They also have sound units. I have them in my tug abd are happy.

The best oil based was the Tomahawk ( no longer available). Certainly produced enough smoke to set the fire alarm off at the E Port Boat Museum show some years ago.
Rather heavy on current draw and most will now use the water based systems producing a fine vapour with no smell. They can certainly produce a visible smoke effect and can be made to realistically puff as the engine speed is varied. Add a sound unit and the effect can be quite realistic.
dave976

Hi Stephen T
I have fitted one of these in my Joffre, Simulation Smoke Generator Unit for Henglong 3918 1/16 RC Hobby Tank, I got my unit from AilExpress, I think for the joffre it puts out the right amount of smoke., it is oil based but I uses glycerine as it is cheaper than smoke oil.
I am working on a unit that uses a usb air humidifier purifier aroma diffuser mini donut that I got of Ebay,
have a look at this http://www.wicksteedparkmbc.com/smoke-generator.html?fbclid=IwAR3UyCp3EgaXwnKSfuviLvc0lgaEIDmOe1jW6oeMRCqECAQ8fNX0u16nW7E

Fred