Evinrude Big Twin: runs on choke only

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Pappy
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Evinrude Big Twin: runs on choke only

Post by Pappy » 07 Nov 2019, 23:52

Photo of the top of the carb not good enough or close enough.
Also want to see a photo of the carb upside down with the bowl off and nothing removed or touched other than the bowl separated from the main body. you said you are going to go through it again anyway.

Newtosa
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Evinrude Big Twin: runs on choke only

Post by Newtosa » 08 Nov 2019, 08:06

Here they are, from when I initially rebuilt the carb in early October. I took these thinking maybe one day I would post the project online, but I didn't get every step. For example, I think I have the wire needle retainer that people sometimes call a spring running through the hole in the brass float arm, which is not shown in the photo.

I've had the carb apart again since then, but the cork jet gasket, float, and seat are all still in place. Do you see anything that looks off? When I get back in front of the engine (next weekend) I can grab some more photos if there's something else you need to see that you think might help solve.
20191006_085057.jpg
20191006_090825.jpg
20191006_090753.jpg

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Pappy
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Evinrude Big Twin: runs on choke only

Post by Pappy » 09 Nov 2019, 00:12

Did you pull the plug on the top of the carb? Can't quite tell if it is the original or not.
If not the replacement plug should have been with the kit. Underneath are around three calibration holes for the idle and off-idle circuits. Debris can get in to the calibration pocket and block one or more holes there.
When you look at the carb again take a look at the high speed nozzle well gasket and see if there is a good imprint on it from the bowl. That has to be well sealed to create the vacuum necessary to pull fuel up to the idle passages.
Edit. While apart make sure that the passageway up to the idle circuit is clear...double check it. While running on choke you are pretty much by-passing the idle circuit.

Newtosa
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Evinrude Big Twin: runs on choke only

Post by Newtosa » 10 Nov 2019, 08:22

Thanks Pappy for the questions. I replaced both plugs, and the photos show my idle circuit holes were clear at the time of initial rebuild (3 medium sized holes in a triangle, and 5 tiny ones above them).

When I get the carb apart again, if a few basic checks don't solve it (idle mix needle packing washers fully compressed, trying the idle mix needle anywhere from 1 to 4 turns out, confirming the nozzle gasket is being compressed by the bowl), I'll need to rebuild the carb to check that all the things that were clear at one time don't have any debris in them now (holes behind the idle circuit plug, float valve needle and seat, watch the idle mix needle with the plug removed to confirm it seats, high speed orifice clear, nozzle holes clear, etc.).

Newtosa
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Evinrude Big Twin: runs on choke only

Post by Newtosa » 10 Nov 2019, 08:33

Onthewater102, did you see anything in the reed / intake photos that looked off?

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Pappy
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Evinrude Big Twin: runs on choke only

Post by Pappy » 10 Nov 2019, 21:15

Typically loose reeds (as in not properly installed during a rebuild) will give you a very hard starting engine that requires a lot of fuel and will only run at well above idle. You should also experience backfiring through the carb......Yours did not. Up to you if you want to check while the carb is off.

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onthewater102
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Evinrude Big Twin: runs on choke only

Post by onthewater102 » 11 Nov 2019, 12:19

My setup was different than yours - I was working on a Merc, where mine weren't seating tight and I could see light through them. They certainly weren't loose, I did not have backfiring through the carb - that's something you won't miss by accident.

I did post about it with pictures when I fixed it...here's the link:

viewtopic.php?f=4&t=43303&hilit=reed
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Pappy
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Evinrude Big Twin: runs on choke only

Post by Pappy » 11 Nov 2019, 21:43

Okay, this thread is going a bit off topic.
Seeing light through the reeds (typically near the tips) is not necessarily something that has to be corrected "immediately".
You have to remember a couple things.
1. The crankcase has both positive and negative pressures going on as the piston travels up and down in the bore.
2. A slight opening in a reed will immediately close with the positive pressure and seal against the reed cage. This is why you never had a backfire through the reeds and out the carb.

Newtosa
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Evinrude Big Twin: runs on choke only

Post by Newtosa » 14 Nov 2019, 21:17

Hi everyone - an update.
. The idle mix needle washers are all fully compressed.
. Idle mix needle out 1 turn to 4-1/2 turns (1/4 turn at a time, run on choke for 15 to 20 seconds before trying to open the choke) didn't do the trick.
. Tomorrow I'll remove the starter, remove the carb, confirm the nozzle gasket at the bottom of the bowl is compressed to create the right vacuum. Will also confirm that high speed orifice is clear.
. If all that looks right, will re rebuild the carb (r&r plugs, float valve needle/seat, every hole and passage, make sure idle mix needle is fully seating, etc.) as soon as the kit arrives. Hopefully tomorrow.

I really appreciate everyone's help with this. Will keep you posted.

Shaugh
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Evinrude Big Twin: runs on choke only

Post by Shaugh » 15 Nov 2019, 10:42

The only other basic idea I'd have is that somehow the float is not opening the valve. It can appear to function without the bowl attached, but a gasket that compresses can protrude and jam the float in the closed position... etc... I'd look hard at that...

Beyond the horses the next step is zebras.... is it possible that someone might have tried to re-assemble the motor before you with mismatched parts ? Based on what we found in the parts diagrams.... The mid year parts changes could have resulted in improper parts being matched to the motor ?

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Pappy
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Evinrude Big Twin: runs on choke only

Post by Pappy » 15 Nov 2019, 10:45

All indications are that you are NOT getting fuel up and into the idle circuit. The choke by-passes the idle circuit and shows you that the engine will run and is properly sealed as it runs pretty evenly and smooth on the choke.
This may have to wait until Monday but I have a carb at the shop for one of these or maybe another at the warehouse that I can check today. Will look at one or both and see if there is anything I am missing.

Shaugh
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Evinrude Big Twin: runs on choke only

Post by Shaugh » 15 Nov 2019, 11:17

Note the differences between carburetors from 60 to 61. It's possible that you're working with mixed parts...

1960:
https://www.marineengine.com/parts/john ... Carburetor

1961:
https://www.marineengine.com/parts/john ... Carburetor

1960 Lark:
https://www.marineengine.com/parts/john ... Carburetor

Note that the 1961 carb shows a donut on the main jet... 1960 doesn't.... etc...

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Pappy
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Evinrude Big Twin: runs on choke only

Post by Pappy » 15 Nov 2019, 19:32

Just remembered that you said you have no high speed adjustment.
This means that you are running a 1961 or later carb on the engine.
Or.....as Shaugh said...maybe a mixed bag of parts?

Edit....fat fingers hit 1962 instead of 1961
Last edited by Pappy on 15 Nov 2019, 21:51, edited 1 time in total.

Shaugh
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Evinrude Big Twin: runs on choke only

Post by Shaugh » 15 Nov 2019, 21:46

Here's a 61 with some good photos to compare.... an unmolested second carb would be the easy way to figure out if the one you have is kerfuffled….

https://www.ebay.com/itm/1961-EVINRUDE- ... SwlQddp3In

a 62:
https://www.ebay.com/itm/DP1C9333-1962- ... SwBOlagfcN
Last edited by Shaugh on 15 Nov 2019, 21:56, edited 1 time in total.

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Pappy
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Evinrude Big Twin: runs on choke only

Post by Pappy » 15 Nov 2019, 21:53

Just for the heck of it take some sealer of some sort and put it around your plug on the top of the carb. See if it is leaking air a bit. Won't take a minute to do it.

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