Best small 50's/60's OMC outboard

thatone123

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On the boards here, you sometime see someone stating that such and such a OMC outboard was simply the best and greatest small outboard out there ever or something to that affect. Is there any reality to that? What engineering or metallurgy would have made this possible. I have run a lot of them from 1 1/2 up tp 18 hp. Some state that various models gave better oil to the bearings and etc. Older models did use a heavy oil mixture. Did that play a part? Did the experimenting with 100/1 ratios in the 80's give shorter lifespans to the OMC's? Just want to get a little input since there is a lot of experience here on this board.
 

oldboat1

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Apr 3, 2002
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'50s and '60s 18s are some of the most popular, and among the best for all around performance. I'm a fan of the pressure tank systems, and run with the original recommendations for oil ratios.
 

jimmbo

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The 5 1/2 hp is a gem. Runs forever, putt putts at idle very smoothly. Had one over 40 years ago. It was used and abused. Overheated severely, submerged it when I flipped flipped the boat, ran it for several days with no oil in the gearcase. Water cooled/lubed gears don't have a long life, neither do the propshafts. It ran from 1964 till we sold it in 1990. Only repairs were water pumps, shift lever, all gearcase internals except for driveshaft. Never touched the power head even after it got hot.
Pre 1955 was pretty much 16:1 gas-oil, most mid 50s thru 1963 ran 24:1 oil mix, some of the 54 - 55s may still have run 16:1. In 1964 OMC switched to 50:1 for the full line. Some engines like the earlier mentioned 5 1/2 weren't completely antifriction bearing motors. The lower crankcase bearing was still a bushing. However even at 50:1 there was enough puddling of the oil to keep it well lubed.
Here's where some disagreements happen... Some of the earlier engines, the 1957 -1959 35 hp were fully antifriction bearinged and could run 50:1. The 1960 - 1963 40hp models were identical bearingwise and clearancewise as the 1964 model and can use 50:1 also. Same can be said for the 1958 - 1963 V4 models. In the 1970s OMC did issue a service bulletin saying their OMC, Evinrude, and Johnson Oils could be run at 50:1 in all of their engines. Myself unless the engine was completely antifriction bearinged, late model 5 1/2 excluded, I wouldn't use 50:1 but the richer 24:1 or 16:1.
The mid 1980s 100:1 issue. Some engines did die younger during this period, but not because of lack of oil while running. If used very regularly and the oil was properly mixed with the gas, they showed no signs of lack of lubrication. It was when they would sit for longer periods of time, especially when owners didn't fog the engine for winter storage. The 100:1 mix just didn't leave enough residual oil on the crankcase bearings and rust formed on the journals.

The 18/20 hp was a classic too, was marketed till the mid 70s. in 1969 - 1977 a hopped up version became a 25 hp
 
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F_R

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Depends on your personal preferences for one thing. Also depends on what specific year/model you are talking about. There were some lemons out there. Your comment could well apply to the Lightwin/JW series. They run great and never give any problems, if in good condition. They just didn't make any bad ones. Everybody has their own opinion concerning fuel and oil. I guess you know the 100:1 mix was quickly cancelled.
 

thatone123

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All interesting! Anti friction bearings? I guess you mean roller bearings on crankshaft and wrist pin assembly? Yes, that 5 1/2 seems like a real god motor for sure. Yes, the 18 is a great motor. I have a 60's model that has the old glass fuel filter. They seem not be quite the power of a more modern 20. I guess that is because of the power rated at the motor instead of the prop? It is amazing how simple and light those 18's are. I have heard that the 100:1 mix worked good especially if the synthetic oil was used. I know some that have run Yamaha for years 100:1 with no problems. For a while I ran my more modern outboards 75:1 synthetic with no problems I could detect. Good info on the oil mix!
 
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HighTrim

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Jun 21, 2007
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The great oil debate is something that you will never get a straight answer online about.

Be wary of advice you get on here. Some advice sounds well thought out, but is complete nonsense! They mean well, but are misinformed.
 

RCO

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I'm going to give my vote to the 5.5 & 7.5 horse. Light, quiet, easy to start, easy on fuel, troll down to a crawl, and the 7.5 in particular will move a small boat on plane at a reasonable pace. The 6 HP CD models that replaced the 5.5 were equally as good IMO.
 

racerone

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There is virtually no difference in powerheads of the later 5.5 and the 6 hp models.----------Both are the simplest / best fishing motor you can own.------The last QD 10 hp models with same wrist pin bearing as a 125 hp motore are top notch fishing motors.
 

jimmbo

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The 5.5 was rated at 4000 rpm, with WOT range of 3500 - 4500. and the 6 was rated at 4500 with range of 4000 - 5000. I recall reading that the head was changed in 1965, and some improvement on the carburation, the first year for the six. It remained a points magneto until 1977 when it got a CD breakerless ignition. They were, and still are good little engines
 

wayne-mayle

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Mar 21, 2017
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High Trim i have a 1952 Fleetwin 7.5 ho mod# 4447, what do i have to do to install a cruise-a-day tank instead of using the small tank mounted on motor.
 
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