1978 Evinrude 3 cyl. Question

[raygussy]

Hey Guys!
I remember a while back reading in a post the only differences between some of the older different h.p. outboards were the carb jets. In other words for the model year 1978 my 70 hp would have the same exact power head on it as the 85 hp, etc. I remember the author stating he had checked part numbers for pistons, intakes, etc. and they were all the same. I just can't find the post now.

Anyhow, I have to put new carb kits in my 78 70hp and I'm thinking why not get the jets for the larger hp motor? My motor is a little undersized for my 18' starcraft center console anyway.
Thanks

 

[mikesea]

Re: 1978 Evinrude 3 cyl. Question

That is not correct.First the 85 is a v-4.The earlier 3 cly.were a smaller cubic inch displacement (49)if I recall.The strokes are different and bore,.What you may have read was the v-4 and v-6 are mostly the same regarding pistons and rods etc.Some 3 and 2 cyl are the same.BUT,regardless,your not going to gain any significant power to make messing with jets worthwhie for the avg,boater.You would need to get into porting,polishing,boring,reed changes,exhust changes and when your done,putting it on a sunday cruiser,you will see little change

 

[raygussy]

Re: 1978 Evinrude 3 cyl. Question

Not questioning your response mikesea, but if that is the case why are all of the part numbers between the three cylinder models for that year the same? (I used a bad example with the 85 v-4, obviously a different setup!) Is it possible that the smaller the hp model the more "tuned down" it is? I know I found it hard to figure too, but how else can one explain the exact same part numbers for a larger motor?
Just wondering...

 

[Chinewalker]

Re: 1978 Evinrude 3 cyl. Question

Not quite the same parts - the cylinder heads show as different and there are two different blocks listed. The porting and head for the 70 is better for low end grunt. The porting and head for the 75 is better for high speed. Most people on most boats simply won't notice a difference. If you have a light hull that responds well to small changes in set-up, props, etc. then you might notice it, but on your 18-footer, probably not.
- Scott

 

[raygussy]

Re: 1978 Evinrude 3 cyl. Question

That's what I wanted to know! Thanks for the info. guys!
Ray