Carb Help

[DWNewt]

Guys, I have a 1977 Evinrude 75hp. I recently rebuilt the engine and have broken it in. Prior to that I also rebuilt the carbs. According to the manual I do not have 1977 carbs on the engine. It appears to be 79-82 carbs because they have 3 orifice holes instead of two, one top center, one top right, and the other lower center. I know the adjustments are wrong because it is slow to plane, dies if I try to apply the throttle quickly and I cannot lower the idle below 1200 rpm. It also sounds as if it is sneezing at idle speed while in the water. Are these orifices adjustible? I looked on the carbs and each one has a number stamped on it. I cannot find any of these numbers in any sites I've checked. Can someone point me in the right direction?<br /><br />Thanks

 

[OBJ]

Re: Carb Help

Maybe knowing some history of the engine would help a little Tech Man. Did you get the engine needing rebuild or did it run prior? Why did it need a rebuild....cylinders scoring/scuffing? <br /><br />Is the sync and link set right? The orifices are replaceable with ones of different size. What I don't know is, if the carbs will work as is on that engine. Dhadley may give us some help when he gets back on. But knowing why the engine was rebuild would probalby be a big help in knowing what to do with the carbs.

 

[Dhadley]

Re: Carb Help

Those carbs should work fine with the stock jets. You may have to adjust the idle air jets down a couple sizes (go richer) to compensate for todays fuel if it's sneezing and the sinc & link is right.<br /><br />At this point I'd soak the carbs again and put in new kits. Let's not chance hurting a new piston. BTW -- That round gasket on the emulsion tube is very important.

 

[DWNewt]

Re: Carb Help

I rebuilt the engine cause I discovered low compression in cylinder #2. The walls of the other cylinders were damaged also. I had them rebored to .40 and installed new pistons and rings. Should the 1st and 3rd carb have the same sized orifice with #2 being a different size? BRP schematics suggest this on most 70 and 75hp Johnson/Evinrudes. At WOT it runs like a scalded dog. No idle problems except the RPM is to high. Just getting it there on throttle. I know my link and snyc is off. These orifices are screw in type, are they meant to be screwed out or seated all the way in to be the normal position?

 

[Silvertip]

Re: Carb Help

If link&sync is off you can fiddle with carbs til dooms day. Start at the beginning and then fix what you are left with when you know everything else is right. Idle mixture and idle speed needs to be set in the water. Not on muffs.

 

[DWNewt]

Re: Carb Help

O.K. will try in the water, how long should plugs last if you only use the boat on weekends and not running the engine WOT for extended periods of time, appx. 15-20 minutes at WOT.

 

[OBJ]

Re: Carb Help

Plugs should last you a couple seasons. Check them once in a while for spark and to see how the are burning. You should be using a Champion QL77JC4 set at .030. Set them at .040 and get a better idle without hurting top end.