1972 100 HP Evinrude Carb issues

[ILLaViTaR]

Hey everyone, I've got a problem with my motor where it seems to run fine at high idle however at low idle, it runs poor and dies after 10-30 seconds.

The other problem is it won't start unless I hand spray some fuel into the intake/carbies. After I spray in the fuel, I can switch it off and start it with ease however if I let it sit for any longer than one hour I need to respray fuel into it again to get it going. (Here's a video of it running/cutting out: ([urlZ]http://www.youtube.com/watch?v=j5JO4E0ZA44[/url]).

I was told my carbies could be the culprit judging from this along with the way it cuts out so quickly in the video.

Well today I took the carbs apart and they seemed extremely clean and I couldn't find any obstructions. but I found one of the low speed orifice plugs had been stripped/overtightened by some dodgy mechanic or something and I can't screw it out, it's not blocked however the head is shredded pretty badly. Could this be causing my problems?

Cheers

 

[emdsapmgr]

Re: 1972 100 HP Evinrude Carb issues

When the engine is at idle, the carb butterflys are closed. The fuel supply goes thru special dedicated idle passages in the carb bodies. If the engine will not idle, these idle passages may be clogged with dried fuel or other debris. The only way to clean these passages out is with a special solvent which will dissolve dried fuel, like a Gumout type product. You cannot see any blockage, as it is hidden inside the passages. As soon as you crack open the carb butterflys, even slightly, other carb jets take over and will run the engine at a fast idle. You may need to pull the carbs apart again.

 

[ILLaViTaR]

Re: 1972 100 HP Evinrude Carb issues

When the engine is at idle, the carb butterflys are closed. The fuel supply goes thru special dedicated idle passages in the carb bodies. If the engine will not idle, these idle passages may be clogged with dried fuel or other debris. The only way to clean these passages out is with a special solvent which will dissolve dried fuel, like a Gumout type product. You cannot see any blockage, as it is hidden inside the passages. As soon as you crack open the carb butterflys, even slightly, other carb jets take over and will run the engine at a fast idle. You may need to pull the carbs apart again.

Hey mate are those the ones under the 2 core/welsch plugs? The carbs are still apart, I haven't removed the two welsch pulgs but underneath them on the butterfly side are 4 tiny holes/passages. Are those the ones you're refering too? I sprayed carby cleaner in where the relative screw plug went and it seemed to pour out all 4 holes just fine without any blockages. The motor idles high but won't for too long in lowest position. Thanks for the help btw!

Cheers

 

[ILLaViTaR]

Re: 1972 100 HP Evinrude Carb issues

Hey mate are those the ones under the 2 core/welsch plugs? The carbs are still apart, I haven't removed the two welsch pulgs but underneath them on the butterfly side are 4 tiny holes/passages. Are those the ones you're refering too? I sprayed carby cleaner in where the relative screw plug went and it seemed to pour out all 4 holes just fine without any blockages. The motor idles high but won't for too long in lowest position. Thanks for the help btw!

Cheers

 

[emdsapmgr]

Re: 1972 100 HP Evinrude Carb issues

I don't usually remove the welch plugs on a normal carb overhaul. I've been lucky enough that the carb cleaner has removed any accumulation in those passage connections under those plugs. I blow a gumout type carb cleaner (with the straw on the nozzle) through a passage in one carb, noting the flow out of the other end of that hole in the carb. Then I do the same passage in the other carb, noting the spray outflow. You want them both to match. Then go on to the next carb hole, repeat till both carbs are done. If you have any restrictions in the passages, you can catch it when you monitor the flow out of the other end of that hole when comparing between the carbs. You will want to remove all jets for visual inspection, then replace.

 

[ILLaViTaR]

Re: 1972 100 HP Evinrude Carb issues

I just checked all the passages and they seem to be clear of any blockage, carby cleaner flows strong through all of them. Regarding the jets, are they the little brass things in the threads that require the special tool screw driver to remove? If so one of the low speed ones has been damaged and had it's head stripped off due to being forced in. Would this cause my engine to die?

 

[emdsapmgr]

Re: 1972 100 HP Evinrude Carb issues

Stripping the special tool slot may not necessarily damage the orfice causing the engine to run badly. If part of the brass jet has been forced over into the jet passage, or if some brass part has broken off and has lodged in the jet-then you can have running issues. Best to try to get it out and visually inspect it. The Bombardier jet screwdriver is part number 317002. About $20.