Carb Jets 1979 75hp Evinrude/ Boyseen reeds Advice

judah34

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So I gave up on my 1976 Johnson 70hp. I purchased a 1979 Evinrude 75hp. I want to put my Boyseen carbon reeds in the new outboard. ON the 70hp I went up 2 sizes on the slow jet per instructions.

The 75hp has 3 jets High/Slow/Idle. Does anyone know should I richen the slow jet like before or richen the idle jets (angled top of carb) and if so are those idle orifices metering fuel or air?
 

ct1762@gmail.com

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if it's and exposed orifice, it's for air. who told you to richen the jets for reeds? i've installed many fiber reeds and never went up any sizes. if you put say a 75hp head on a 70hp then i'd say yes go up a size or 2 on the mains, ditto for removing air silencer. hate to say this, but the 75hp only has power on top end. the 70hp had alot more low-end grunt. hope its on a light boat youll see what i mean!
 

flyingscott

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The low speed orifice needs to be richer by 2 sizes. This prevents lean sneezes from blowing out the reeds. I would leave the original reeds in because Boyesen reeds will provide a negligible improvement.
 

racerone

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Saw a set of composite reed buckled / damaged on a V-6 one time.------They did install composite reeds at the factory at one time.----But they had a note stating ----" these reeds have a limited life / number of hours at continuous full throttle operation "
 

judah34

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Thanks Folks, I already have the reeds so I figured why not. replace the steel ones that are most likely originals from 1979. Motor is going on a 800lb boat so not too worried yet.

I am just following the directions from Boyseen. But the 3rd jet top side of the carb made me confused. Maybe some CCMS with stuffers? I have heard no jetting needed.
 

ct1762@gmail.com

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The low speed orifice needs to be richer by 2 sizes. This prevents lean sneezes from blowing out the reeds. I would leave the original reeds in because Boyesen reeds will provide a negligible improvement.

Why would you need to go up 2 sizes on Boyesens, and not on CCMS reeds? Only every installed CCMS. assumed composite reeds were all similar ie. not different enough to warrant an orifice change?
 

Faztbullet

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The Boyensen reeds will be lucky to live 2 years before splitting or breaking. Chris's (CCMS) or Tony's(TDR) ae bolt in and go and new had a problem with em
 

flyingscott

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Why would you need to go up 2 sizes on Boyesens, and not on CCMS reeds? Only every installed CCMS. assumed composite reeds were all similar ie. not different enough to warrant an orifice change?

Boyesen Reeds are 2 stage reeds, there is a thin one for low speed improvement and a thicker section which lifts at high speed. The thinner one is VERY easy to damage and a lean sneeze will blow it right out. The CC reeds are a direct replacement for the steel reeds so they are thicker and one piece.
 

ct1762@gmail.com

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ohh makes sense now. didn't realize that's how the Boyesen's were designed. seems a bit more delicate.
 
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