Off idle orfice.

[Gulfhorse]

HAs any heard of removing the off idle orfice/jet to reduce off idle bog. I was told that there was a recall on these 79 70hp seahorses, however not all were fixed. I believe i have one that did not get the memo. A local mechanic told me to remove the jet and it should fix the problem. What do yall think? Sounds reasonable to me.

 

[jtexas]

Re: Off idle orfice.

He wants you to take out all 3 off-idle jets? I have a '79 70 -- I never heard that and, I'm pretty skeptical. I'm not the original owner though, so I can't dispute. Isn't that like replacing a 0.035" hole with about a 1/4" ? (obviously, I'm no engineer either ).

I have struggled with it at times though -- getting the throttle cable adjusted just right, the throttle pick-up point, and the idle speed set high enough seem to be the keys.

I'm dying to know if it will run at all missing a jet.

 

[Gulfhorse]

Re: Off idle orfice.

With the model that i have, there are no adjustiments for idle speeds. The jets are fixed orfices. I myself am skeptical but it seems reasonable,because I can choke the motor right when it begins to bog and the motor wil pull through the bog as if it is running lean on fuel. I am going to remove the jet orfices to determine if this is a solution or not next weekend. I will post my results. Anyone have any more thoughts on this issue. thanks

 

[levi_tsk]

Re: Off idle orfice.

worse case scenrio you foul a couple plugs cant see what it would hurt?

 

[Joe Reeves]

Re: Off idle orfice.

Having worked on those engines even when they were new, I do not recall any such bulletin. I've since (today) went thru all of the OMC bulletins I have pertaining to fuel and have found none relating to what your mechanic spoke of. Should he have this bulletin/memo, I'd like to have a copy of it for my records.

However, that jet measures fuel, and to remove it effectively results in enlarging that fuel passageway to a "flood" situation. There was a bulletin which pertained to the 1976 70hp model carburetors which detailed modifications to the carburetors (removing of parts) but this was not needed on any carburetors later than 1976. Are you positive that your engine is a 1979 model?

Don't discard the jets. Bogging when the throttle is applied is usually due to faulty synchronization, fouled carburetors, throttle butterflies opening too soon.

 

[jtexas]

Re: Off idle orfice.

this pic is a later model, but the idle set screw is the same. make it 750-800 in gear in the water.

 

[Gulfhorse]

Re: Off idle orfice.

Yes the motor is a 79. I preciate the info everyone. I will remove them and see what happends. The mechanic i do not know personally but he told me " Im not supposed to say this, but if you take out the off idle orfice she will run great." He said, " we have made this modification nummerous time with great success." Thanks o all i'll let you know my what happens when i get in the water this weekend.

 

[Cofe]

Re: Off idle orfice.

Interesting topic about those carbs.
I noticed on the evinrude site, that they list the orfices for a 75hp motor in the 70hp catagory. They also show different orfices in each carb.

Here is the link.........http://shop2.evinrude.com/Index.aspx?s1=o967siu2o15b78tec8seqe4i06&catalog_id=0&siteid=1

 

[jtexas]

Re: Off idle orfice.

The 70 and 75 hp motors are basically the same motor; about a half-dozen or so part numbers are different. All the repair procedures are the same; they share a common parts catalogue & repair manual.

Middle carb on the 75hp has a 1/1000" larger idle jet than top & bottom. They're all the same on the 70, though.

One thing I can tell you from personal experience, the idle and intermediate jets have the same O.D., and if you accidently swap 'em, that cylinder won't idle. Don't ask me how I know

That motor isn't even going to think about running with jets missing -- once the throttle valves open just a tiny bit, it'll flood and die.