What the Fuel mixture for 35 hp outboard?

Answer 1

The gas/oil mix ratio is not motor dependent unless the motor uses bushings, not ball or roller bearings. Frankly, I have not heard of one of these being made later than about 1920, so unless you have an unusual antique, the mix is determined by the oil.

Let me restate that. There are some plain bearing two strokes, but unless you are addicted to the difficult side of life and are wealthy enough to afford the fuel, you probably won't be using engines that small. Some currently manufactured model airplane engines DO use plain bushings. They are usually under one cubic inch of displacement however.

Most manufacturers of two stroke engines use roller bearings on the rod, and ball bearings on the crank. Some use roller bearings all around. The clearances are going to be so close to identical between manufacturers as to be identical. Same is true in the piston to wall clearances. Even the piston and bore material is nearly identical between all manufacturers. To keep these surfaces from contact, two stroke oil must meet a particular criterion for viscosity and weight. Make it viscous and synthetic, and the oil manufacturer may specify a 100 to 1 mix. Make it less viscous, and a lower specific gravity, and the oil maker may call for only 40:1. The oil varies maker to maker far, far, more than the nearly similar engines. So it is the oil that must be considered to get the reccomended mix ratio, NOT the brand of engine.

The oils vary widely, and most engine manufacturers will have an association with an oil maked to produce oil under the engine makers label. So the motor specifications will read: Use Honda Brand Synthetic oil at 100:1 for best results... That is what determines the manufacturers reccomendation for the mix ratio. However there is nothing stopping you from using say, Castrol synthetic, at Castrols recommended mix FOR THAT PARTICULAR OIL. Lets say that Castrol suggests you mix their XYZ Super Racing Oils at 140:1. That would be the oil mix to use even if your Suzuki Gudzilla 1100 manual suggest a mix ratio of 25:1. Or, if you want to run a good petrolium based oil, let's say say Torco in this case, and Torco recommends a mix of 50:1 for sport riding, and 35:1 for constant pedal to the metal racing, then follow Torco's recommendations. The mix is oil dependant, not motor dependant. That is the final answer.

Where people get into trouble is by absolutely relying on the manufacturers numbers for the ratio, but changing oils. As example, the manufacturer may recommend a ratio of 100:1 and specify their own brand of super slippery synthetic. That particular oil is formulated for that thin of a mix and it works perfectly. However, the owner forgets that it is the type of oil that makes or breaks the motor and puts in 30 wt chainsaw lube at 100:1 then rides like the wind passing cars like they were stationary. Soon he seizes it solid and can't understand why. he's pissed.

Later, we see this guy, as he stands at the service counter begging for warranty. He's smoked his engine big time and he can't understand why. He says for the third time: ""But I mixed the oil like it sez in the manual, man. This is BS man, it's under warranty!" And the service manager will politely shake his head and once again give his usual oil ratios speech. "If you read the manual, it very clearly states that the 100:1 reccomedded mix is using Honda Super slippery Synthetic XYZ oil, not Husvarna chainsaw lube." He's said this a thousand times and he's sure he'll say it a thousand more. It's a tough one, but there will be no warranty.

I know about that speech because I was that service manager working for Honda, Yamaha, Kawasaki, Suzuki, Hodaka, Bultaco, Montesa... on and on. Even Coswalds and Coopers. Just to mention the two strokes. I even managed a shop that worked on DKW two stroke cars (very nice vehicles). Also, I worked for Torco oil and repped Castrol throughoput California. I have nearly 40 years in the business and if you came before me with your "What mix should I use" question. You would get the same infoirmation that I have provided here. Read the bottle. That gives you the mix.

Here is the final say. If you want to race, ask your racing friends what oil they run and run the oil and mix they use. Otherwise, almost any recognized brand of two-stroke oil anywhere close to the OIL manufacturers reccomended ratios will be reasonable and safe. It won't create a problem if you are off a bit. As example, Chevron two-stroke oil... they recommend 50:1, but if you mix it at anywhere from 35 to75 to 1, and you run the motor normally, not beating it through lugging or excessively high rpms and a lot of heat, and you will probably be just fine. I have to put in the "probably" here because even if it was perfectly mixed at the optimum ratios, you still COULD have a problem.

I once made six trips between Salt Lake City and San Jose Calif riding a 1973(?) Kawasaki K series 125 at freeway speeds. I used whatever oil was available at where ever I was. I didn't have oil injection or a mixer bottle, so I often used coke cans and guessed at the ounces, and guessed at the gas too. I made all those trips on the same little engine. It would occasionally smoke excessively, and I did seize it several times, but that was from following a truck so close that there was almost no wind across the fins. It was overheating, not oil starvation. Still, I rode. I was in l;aw school and I would go home to san Jose between semesters. The little Kawasaki never quit.

It's not rocket science, so don't get too pickey and use the oil makers reccomendations not the engine manufacturers. The oil maker will have a series of reccomended mix ratios listed on the back of the can, bottle, etc. Just choose the one that is best for the type of riding you do. Keep it in moderation and everything will be grand.

Good riding.