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Author Topic:   General Mechanical Questions

Owen Schultz posted 04-23-2003 04:24 PM ET (US)
(1) What is the advantage of oil injection for an outboard motor? Isn't it safer to mix the oil right in the gas so that you would never have to worry about the oil injection system failing?
(2) It is my understanding that outboards went to 4 stroke because they burned cleaner but that now there are new 2 strokes that burn cleaner than 4 strokes. I have also heard that 2 strokes are louder than 4 strokes. However, I ve been told that 2 strokes generate more power with less weight. Can somone sort all of this out for me? If one had to buy a new 90 Hp motor what would be the optimum choice?

jstachowiak posted 04-23-2003 05:33 PM ET (US)
This subject has been talked about extensively on this site. Try doing a search: http://continuouswave.com/htdig/ search "4 stroke" and see what you come up with.
To answer your first question, yes premixing oil would be "safer" but most oil injection systems meter the oil out from 50:1 to 100:1 dependent on rpm's consequently using less oil.
Your second question answer, as you will see, will keep you up very late at night reading just the posts in the last 100 days.
Good Luck.
p.s. the best motor for a 17 Newport, Montauk or Classic is a Suzuki 70HP 4 stroke.
jimh posted 04-23-2003 07:52 PM ET (US)
Re (1) The advantage of automatic oiling of 2-cycle engines is that it relieves the operator from having to pre-mix the fuel supply. There is also the possibility of varying the mix ratio in proportion to the throttle setting, generally done with an eye to reducing the amount of oil used at idle and slow speeds.
This is a more complicated system than one without the automatic mixing and thus it probably is more prone to failure.

Re(2) Outboard makers went to new technologies primarily to be able to conform to arbitrary emissions standards being imposed on them by the government of the United State of America. The government of the state of California has imposed even more strict emission standards, and this has also affected the design of outboard engines.
If outboard engine makers were designing their new engines only for improved performance, for increased reliablity, or decreased weight, they would probably look much different than the current product line.
The primary purpose of the new engines is to conform with the requirements to meet emission standards, and any other benefit that comes with that goal is secondary.
jimh posted 04-23-2003 08:47 PM ET (US)
Also, with regard to the rate of failure in mixing oil and gas in the proper ratio:
You could suppose that the operator of the boat will never mix the gas and oil in an improper ratio, but that is quite an assumption. Thus the failure rate for the human-mixed fuel and oil mixture might well be much higher than the failure rate of the mechanical devices in the engine which do this.
The exact failure rates would depend on how well the mechanical system was designed (and maintained) and how accurately the boater can compute ratios of volumes of fluids when he gets to the gas dock.

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Author	Topic: General Mechanical Questions
Owen Schultz	posted 04-23-2003 04:24 PM ET (US) (1) What is the advantage of oil injection for an outboard motor? Isn't it safer to mix the oil right in the gas so that you would never have to worry about the oil injection system failing? (2) It is my understanding that outboards went to 4 stroke because they burned cleaner but that now there are new 2 strokes that burn cleaner than 4 strokes. I have also heard that 2 strokes are louder than 4 strokes. However, I ve been told that 2 strokes generate more power with less weight. Can somone sort all of this out for me? If one had to buy a new 90 Hp motor what would be the optimum choice?
jstachowiak	posted 04-23-2003 05:33 PM ET (US) This subject has been talked about extensively on this site. Try doing a search: http://continuouswave.com/htdig/ search "4 stroke" and see what you come up with. To answer your first question, yes premixing oil would be "safer" but most oil injection systems meter the oil out from 50:1 to 100:1 dependent on rpm's consequently using less oil. Your second question answer, as you will see, will keep you up very late at night reading just the posts in the last 100 days. Good Luck. p.s. the best motor for a 17 Newport, Montauk or Classic is a Suzuki 70HP 4 stroke.
jimh	posted 04-23-2003 07:52 PM ET (US) Re (1) The advantage of automatic oiling of 2-cycle engines is that it relieves the operator from having to pre-mix the fuel supply. There is also the possibility of varying the mix ratio in proportion to the throttle setting, generally done with an eye to reducing the amount of oil used at idle and slow speeds. This is a more complicated system than one without the automatic mixing and thus it probably is more prone to failure. Re(2) Outboard makers went to new technologies primarily to be able to conform to arbitrary emissions standards being imposed on them by the government of the United State of America. The government of the state of California has imposed even more strict emission standards, and this has also affected the design of outboard engines. If outboard engine makers were designing their new engines only for improved performance, for increased reliablity, or decreased weight, they would probably look much different than the current product line. The primary purpose of the new engines is to conform with the requirements to meet emission standards, and any other benefit that comes with that goal is secondary.
jimh	posted 04-23-2003 08:47 PM ET (US) Also, with regard to the rate of failure in mixing oil and gas in the proper ratio: You could suppose that the operator of the boat will never mix the gas and oil in an improper ratio, but that is quite an assumption. Thus the failure rate for the human-mixed fuel and oil mixture might well be much higher than the failure rate of the mechanical devices in the engine which do this. The exact failure rates would depend on how well the mechanical system was designed (and maintained) and how accurately the boater can compute ratios of volumes of fluids when he gets to the gas dock.