History of the 3 cylinder OMC

[theoldwizard1]

I have read a lot of good things about this engine ! About the only downside I have ever heard is that they are thirsty ! :laugh:

I would like to know the history of this engine, specifically what years it was produced, various horsepower ratings and significant improvements made over its life.

Thanks

 

[seahorse5]

Re: History of the 3 cylinder OMC

Came out as the first loop scavenged engine from OMC and had thru-hub exhaust as a 55hp in 1968. 49 cubic inch

over the years it was upgraded to a 60, 65, 70, and 75. There was also a racing version for a few years that was said to be around 90+ hp

 

[emdsapmgr]

Re: History of the 3 cylinder OMC

These early-year units had a difficult time making any real torque, considering the 75 hp makes it's hp out of just 49 cubic inches. The fact that these early 75's (only) were a high port (high revving) just made the torque issue worse. Somewhere around the 1990 timeframe, the blocks were increased to 56 cubes, making the engines seemingly a lot more powerful. These loopers have been historically pretty bulletproof and seem to run for years without much sign of wear. I have had two, a 76 75 hp and a 92 70. The bigger cubic inch 70 has much improved torque, yet still breathes well at 5700. The only issue is that they don't idle as smoothly as I'd like, but I'm comparing them to V4's and V6's. I really like my 92 and am very happy to live with it's idiosyncracies. Around 1986 OMC changed hp ratings from crank hp, to prop hp. So the later (1986 and up) units actually make about 10% more true hp than the 1985 and older ones.

 

[Chinewalker]

Re: History of the 3 cylinder OMC

Thirsty? Hardly! Comparatively so, anyway. My 1980 Stinger 75 drinks substantially less fuel than my 1983 Johnson 90 V4.

 

[BigB9000]

Re: History of the 3 cylinder OMC

the only downside I have ever heard is that they are thirsty ! :laugh:

I don't think a majority of people here would get that joke.
Urban Dictionary: thirsty

 

[82rude]

Re: History of the 3 cylinder OMC

I had the 68/69 Johnson 55 hp looper.rock solid dependable.that thing was used for salmon fishing and trolled day in day out, all day, all week, with nary a peep out of it.believe it was elect shift also if im remembering correctly.one of the best motors I ever had .heres a site that might interest you.http://www.old-omc.de/index2.html

 

[theoldwizard1]

Re: History of the 3 cylinder OMC

I don't think a majority of people here would get that joke.
Urban Dictionary: thirsty

I did not mean that interpretation. I'm too old to use any definitions out of the "Urban Dictionary" !

 

[F_R]

Re: History of the 3 cylinder OMC

Well whatever definition, they certainly were not thirsty. The old 55hp used less gas than a 33 and would outrun the old V4-75hp motors.

 

[HighTrim]

Re: History of the 3 cylinder OMC

I have a '76 55hp on a light 16' aluminum that runs like a scalded ape!

 

[racerone]

Re: History of the 3 cylinder OMC

A 76 OMC 55 HP would be a high rpm 2 cylinder model.

 

[jimmbo]

Re: History of the 3 cylinder OMC

The 75hp from 49.7 cu in has the same hp/cu in as the merc inline 6 150hp. Great engines in the 4000 - 6000 rpm range, a little weak on the low and mid range.

I agree with F_R about how the 3 cyl 55 performed.