A number of chemical compounds are necessary for the operation and maintenance of outboard motors; 2-cycle engines require 2-cycle oil, of course, and then there is the matter of lower unit grease/oil. Those are the two "biggies," but there are other chemicals one needs to be aware of, if for no other reason than some should be avoided.

First it must be stated that if one owns an outboard motor that is still covered by a warranty, it would be best to follow explicitly the recommendations of the manufacturer. Using products not specified or endorsed by the OEM may void one's warranty. For an outboard motor with no warranty concerns, the following are my opinions:

When it comes to what kind of oil to mix with the gasoline, one will often run across some strange recommendations as to what type of oil to use. For example, I am looking at the original specs. for a 1940's outboard and the recommendation was to use SAE #40 oil, which is not really a 2-cycle oil. What one must keep in mind is that until the mid 1960's there were very few true 2-cycle oils available and one had to use what was on the market. Without exception, I use modern 2-cycle oil in all of my outboards, regardless of what the original recommendation was. I buy mine in gallon jugs from a nation-wide "big-box" retailer that I won't name, but which was founded by a guy named Sam from Arkansas. It is about the cheapest 2-cycle oil I have found and as old outboards have "richer" oil mix ratios than newer outboards, the price of oil can be a consideration.

While on the subject of oil mix ratios, I should mention that I ALWAYS mix-in at least as much oil as the factory recommended. There are those out there who will claim that modern 2-cycle oils are so much improved over the old oils that one can get by just fine by mixing at a "leaner" ratio. This may or may not be true, and may be true for some models but not others. The bearing arrangements in the 1950's OMCs, for example, were sometimes different in different models and what might work well for one model could lead to disaster in another model. Also keep in mind that for "heavy-duty" use or for racing, it was often recommended that the amount of oil be increased.

The original spec's for the 1950's OMC outboards that I usually run USUALLY called for an oil ratio of 24-to-1, or twice the oil used in the 50-to-1 ratios that most late model outboards use. I run these engine at ratios of about 16-to-1; even richer than the original recommendations.

In the "old days," this could lead to spark plug fouling but the new oils are so much improved that I have not fouled a spark plug in an outboard in over 10 years.. I did manage to foul one in my new 4-cycle lawn mower early this spring, however, when the air filter plugged-up with dust and the engine, starved for air, ran too rich.

An added benefit of running a rich mixture is residue oil that coats the internal parts of the power head. I never bother to "fog" the power head "innards" as usually recommended before long-term (winter) storage and have never had a problem because the "rich" oil ratio leaves behind plenty of oil to protect the power head from internal corrosion. Back in the 1980's OMC was selling small outboards labeled with 100-to-1 oil mix ratios, but later changed that to 50-to-1. The change was not due to inadequate lubrication, but because the there was a danger of internal corrosion during storage.

The second chemical we need to deal with is lower unit oil/ grease. What I use in my 1950's OMC's is "house-brand" lower unit oil from the big-box retailer. Just like the 2-cycle oil, it is about the cheapest lower unit oil out there, which is important to me because most of my lower units leak a bit and so I will drain the resulting oil/water mix often. I suppose I could try to "re-seal" the lower units but getting one of these old two-piece lower units sealed water-tight can sometimes be a problem. For example, if the shaft seal is leaking because the prop shaft was scored by fishing line wound around it, replacing the seal is not going to stop the leak for very long. Rather than mess'n with the lower units I just drain and replace the lower unit oil frequently. The smaller old OMC engines have bronze bushings as bearings for the shafts in the lower units and a little water does not seem to hurt them too much as long as the water is not allowed to displace most of the oil and as long as the water is not allowed to remain in the lower unit for long. And certainly you want to drain and refill with fresh oil before freezing weather sets in for the winter. There is an alternative for those with especially leaky lower units. The Lubriplate company sells a white grease called Lubriplate 105. This grease is sold as both an engine assembly grease to the automotive trade, and also as a lower unit grease for non-shift outboard motors. Most of the outboards that I recommend for "cheap power' seekers (OMC products made between 1955 and 1972-or-so) used oil and not grease in the lower units, but Lubriplate 105 is widely recognized within old-outboard-circles as being fine for outboards without a gearshift. I have even seen it used in a few outboards with gearshifts that had especially leaky lower units. The grease will "wash-out" at a much slower rate than oil. One still needs to frequently drain water from the lower unit and add additional grease, however. About the only way to totally remove Lubriplate 105 from the lower unit is to disassemble and scope it out.

Others will point out that using a heavy grease in a leaky lower unit is tantamount to using very heavy oil in a well-worn auto engine; a "slip-shod" way of getting a few more miles out of the engine. And I agree, but what is the point of putting a lot a time and effort into making the lower unit "good as new" when the power head to which it is coupled is far from "good as new?" Anyway, if you want to try the Lubriplate 105, it should be available through a good auto parts store. I would not substitute another "white grease" for the :Lubriplate.

I have heard that gasoline is starting to get expensive (duh) That's one good reason to save any gasoline left-over at the end of the season. Another reason is that the proper (legal and safe) disposal of old gasoline can be a real hassle and a real expense. But gasoline that sits too long can go "bad." the thing to do is to add a little gasoline "stabilizer" as you get near to the end of your boating season. Again, this is something that the big store started by Sam has, and like the 2-cycle oil and the lower unit oil, you can even buy this stuff at auto parts stores and even boat dealerships. Follow directions on the bottle. It is a lot easier to mix in as you add gasoline to the can than to mix it into a can that is already full. I will confess to using a lot of "last year's gasoline" that I forgot to add stabilizer to and having no problems with it. If possible I do try to add some new gasoline (and oil, of course) to "freshen up" the old fuel mix a bit.

As previously mentioned, spark plug "fouling" used to be a fairly common problem with 2-cycle engines. And as also mentioned, the new 2-cycle oils rarely cause a fouling problem. Still, carbon deposits in a 2-cycle outboard (the deposits which foul plugs) are still a concern. While cleaning or changing spark plugs is usually more of an annoyance rather than a real concern, carbon fouling of exhaust passages and piston ring grooves is a much more serious problem. Blocked exhaust passages often require a partial disassembly of the power head in order to remove the carbon, while piston rings that are "stuck" in their grooves can require a complete power head disassembly to correct. In that case it is usually wise to install new piston rings since the power head is apart anyway and the rings (if they are available) are usually not all that expensive.

There are (2) types of chemical carbon removers that are readily available; one is a liquid that can be mixed in with the fuel, while the other is an aerosol that can be sprayed into the carb. air intake of a running engine, or can be sprayed into the exhaust passages (once the passage covers are removed) of a non-running engine with stuck rings. I like to occasionally mix a bit of the liquid (less than the recommended amount) into the occasional tank of gasoline, but I do not use the remover in every tank of fuel I run through my engines. I also keep some of the aerosol around as a "last-ditch" effort to be used on engines with low cylinder compression where I suspect that the piston rings may be stuck rather than simply worn. In that event, I will spray the remover in through exhaust passages and spark plug holes and allow the engine to soak in the remover for days. Be advised that the liquefied carbon that will flow out of an engine thus treated will make an unbelievable mess of anyplace the engine is sitting.

Finally, there are some chemicals which I would advise that you avoid. Engine starting fluid is one. We all know that it is bad for engines because it "detonates" so violently in the combustion chamber, and also because it can wash the lubricating oil off moving parts within the engine. Yea, I do very occasionally resort to starting fluid but I don't make a habit of it, and since I have literally dozens of engines laying around the place, ruining one will not change my "outboard situation" much. Do you have so many outboards that your situation is the same?

Other fluids I would suggest avoiding are automotive carb. cleaners which one mixes in with the gasoline. Most of these advertise that they remove "varnish." The cork carb. floats in most of the old OMC's are varnished cork. As with starting fluid, the cleaners can wash the oil from moving parts, reducing lubrication. If you suspect that your engine is running poorly (or not at all) because of a dirty carb., then remove the carb, take it apart, clean it, and install a rebuilt kit. However, if you are going to insist of mixing carb cleaner in with your gasoline, make sure it is a type specifically recommended for 2-cycle engines.

One last chemical I would strongly recommend that you avoid while operating your boat: Alcohol.

The kind that you drink.

All of the above are my opinions.

And I always have some.

Max