Re: Two OB's One drips oil from exhaust after usage the other is dry, why ?
Too many variables to say exactly why one oozes goo and the other doesn't unless we know much more.
If the 9.9 runs colder, bad thermostat, no thermostat, used for trolling all the time, floats set higher, low speed adjustment on the rich side, colder plugs, different load/wrong prop, etc, it may be much more likely to drip.
All my kickers drip to a certain extent depending the oil I use, and how they get used. The main motor never drips and they run the same fuel.
The main motor runs at higher RPMs almost the entire time and at full operating temperature, never trolling at an idle, the kicker is at almost at an Idle for many hours on end.
The goo is from exhaust and water combining in the mid section and sticking to the housing, when water and oil mix the combination becomes more viscous and sticks inside the housing. This happens more at low RPMs when the exhaust and cooling water is colder, at higher RPMs there is less water in the housing, plus it's hotter and being forced out much faster. There is also less unburned fuel in the mix.
As the water evaporates out of the housing over time, the viscosity of the mix drops and the unburned fuel begins to drip out, it will also change color, back to a darker fuel and oil look.
As for plugs, hotter ones typically help to keep the temp up which results in better combustion and less goo, good for low speeds, but not so much for high RPMs. Whether one brand does better than another is sort of hard to determine, companies have heat ranges for each plug, they don’t necessarily match up closely with another brand, so one brand may say this is the plug to use because it’s the closest one they have for what came stock in that motor. It could be slightly colder or hotter and you don’t really know unless you actually test it yourself, which isn’t something most people are going to do. So when someone says I switched to XXXX brand plug and it worked better or worse, it may just mean that the heat range was or wasn’t right for how they used the motor. Simply going up or down one range may have that brand work great, or not at all.
Big companies tend to have many more plugs and they can be closer in temp, so fine tuning can be easier. Smaller companies, with supposedly high performance plugs tend to have fewer options, so one plug needs to cover a wider range of temps and motors. If the specialty plug for your motor is slightly hotter than stock then it may run a little cleaner at low speeds, resulting in less goo. Sometimes the stock plugs are slightly on the cold side, thinking it’s better to error slightly on the cold side than hot, so if you use it for trolling you may need to go one range hotter for best performance.
