Postby jimh » Wed Nov 15, 2017 11:45 am
I will offer a few remarks on the basis that I qualify because I have met the criterion of having re-powered a Boston Whaler boat.
If your present outboard engine is running and working well, there is no possible economic incentive to replacing it with a new engine. You will never recoup the cost of the new engine in any actual savings from reduced operating expenses. This is particularly true for a modern two-stroke-power-cycle direct-injection engine like the OptiMax. That engine gets good fuel economy. There won't be any real chance to save operating expenses by using less fuel.
The objections to you have to the OptiMax are the noise and smell. The noise of the OptiMax is noticeably greater at idle and very low speeds. There is no workaround for that noise. You cannot bolt-on reduced noise; it has to be designed into the engine. If you keep the OptiMax, is will be noisier than other engines, particularly at idle speeds.
The objection to the smell may be possible to remedy. What oil are you using in the OptiMax? Try the Mercury-branded, premium, recommended oil for that engine. It is probably a low-ash, semi-synthetic oil blend. It may burn cleaner and produce less exhaust smell.
Note that all outboard engines have an idle exhaust bypass system that permits the engine exhaust at idle RPM and very low boat speed RPM to exit the engine directly into the air. Once the boat speed increases, the engine exhaust is mostly directed to an underwater exit, and you should not be able to smell it.
The only time I can smell the exhaust of my outboard engine is when the boat happens to be on a course that is directly downwind, the boat speed is very slow, and the exhaust from the idle exhaust bypass is being blown by the wind into the cockpit. This does happen on rare occasions. But you will get the same situation with a four-stroke-power-cycle engine; you will be sniffing its exhaust, too.
The exhaust smell in a two-stroke-power-cycle engine is a result of the eventual combustion of the lubricating oil in the cylinders. The smell produced varies with the type of oil. On my boat, I use a nearly full-synthetic premium oil that burns with very little ash and leaves behind very little deposits. It does have an odor, as I can smell it when we are in that downwind situation. But it is not an overpowering odor--it is mostly the combustion exhaust that I can smell, not so much the oil smell. Also, with my engine (legacy E-TEC V6 3.3-liter) I have the option to select a lower oiling rate if I exclusively use the premium oil. I have selected that optional lower oil rate, and my engine has less oil to burn than at the usual 1:50 oil-gasoline ratio used in many two-stroke-power-cycle engines.