Evinrude Big Twin: runs on choke only

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Shaugh
Posts: 596
Joined: 20 Jul 2015, 11:19

Evinrude Big Twin: runs on choke only

Post by Shaugh » 15 Nov 2019, 22:06

I always try to keep a 2nd parts motor of anything that I have in service for me.... a 2nd carb brings to mind a similar story.... my 58 35 hp ran ok... but just seemed to be lacking that full throttle anger that I expected... on a whim one day I took the carb off a 59 35hp parts motor I had in the stable... cleaned and rebuilt it... put it on the 58 and it suddenly ran like a scalded cat... never could figure out why....

A second carb would be a cheap addition to your arsenal...

RazorBaits
Newtosa
Posts: 45
Joined: 17 Apr 2018, 00:05

Evinrude Big Twin: runs on choke only

Post by Newtosa » 16 Nov 2019, 17:29

Thanks again to both of you; it's nice to know you're out there trying to help me get this one put to rest.

I looked through marine engine.com, my manuals, and some photos. Looks like I do have the 61 carb, so at least it's matched and I was looking at the right schematics, etc.

I pulled it off this morning. It was a lot dirtier than I expected, for something I rebuilt in October. High speed orifice was oozing dirty fuel mix, and the cavity behind the idle Welsh plug was nasty. If I hadn't taken the photos, I would have thought I just imagined having rebuilt it. Bowl was clean, oddly. Cork packing gaskets were falling apart. Idle mix needle hole (where the brass needle seats) was plugged with some kind of goo. Looked like caulk... Surely not. Although my original photos show the 3 main holes and 5 smaller ones leading to the carb body were completely clear, I don't remember checking that mix needle hole the first time.

Fuel filter and pump screens clear. Nothing visible in the tank or lines (this is the setup I use regularly on another engine). The only 2 things I can think of:
1. That idle mix needle seating hole might have been clogged all along. I didn't see anything else like that during the initial rebuild, and I don't remember checking it (and no photos of that hole, so I bet I didn't look at it).
2. After the power head rebuild and carb reassembly, I put the engine on a stand on the back of my truck to take it to the lake. Didn't put the cowling on, and my truck bed usually has dirt and mulch in it from a yard project. Could that much dirt have swirled around and then made its way into the carb? Never even heard of such a thing, but I can't think of any other explanation.

Back together now. One question before I install and try again. The schematic shows the following order for the idle mix packing: cork, plastic, plastic, cork (with the bushing under all that, and the nut on top). I had installed plastic, cork, cork, plastic. Does that matter? Which way is correct? My 70s ones all have a squishy red plastic one -piece, so this one isn't as familiar to me.

Newtosa
Posts: 45
Joined: 17 Apr 2018, 00:05

Evinrude Big Twin: runs on choke only

Post by Newtosa » 16 Nov 2019, 17:34

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Newtosa
Posts: 45
Joined: 17 Apr 2018, 00:05

Evinrude Big Twin: runs on choke only

Post by Newtosa » 16 Nov 2019, 19:50

All good. Thanks to everyone who encouraged me to stay focused on the fuel.

Newtosa
Posts: 45
Joined: 17 Apr 2018, 00:05

Evinrude Big Twin: runs on choke only

Post by Newtosa » 16 Nov 2019, 22:31






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Pappy
Donor
Posts: 2837
Joined: 15 May 2010, 00:38
Location: Central Florida

Evinrude Big Twin: runs on choke only

Post by Pappy » 16 Nov 2019, 22:51

Plastic cork cork plastic is fine as the plastic is acting like a bearing surface and the cork will compress.
Glad you got it running without going to some of the extremes that were suggested. BTW - I was down at an antique outboard meet today and had a chance to look at a 57 35hp carb. I was looking for anything I had missed and found nothing yet we knew it had to be in the idle circuit.
What did the debris look like? By chance was it the same color as the diaphragm in the fuel pump? Just an educated guess that the diaphragm in the pump may be on it's way out and what it is shedding is going through the carb. check it.

Newtosa
Posts: 45
Joined: 17 Apr 2018, 00:05

Evinrude Big Twin: runs on choke only

Post by Newtosa » 17 Nov 2019, 01:01

Thanks Pappy. The debris was more sludgy and brown than synthetic and black. I checked the fuel pump today even though it was rebuilt and the diaphragm was replaced in October (I agree it made sense given all the dirt I found today). Everything was clean in the pump.

I still need to get it in the water with the prop on and get the carb tuned (right now it's only 3/4 turns out and idling a little high and rougher than I'd like), but I'm really happy that it's running at this point.

Shaugh
Posts: 596
Joined: 20 Jul 2015, 11:19

Evinrude Big Twin: runs on choke only

Post by Shaugh » 17 Nov 2019, 14:35

It's a good lesson for all. No matter how diligent and well informed, as you certainly were, there should always be the first assumption that you likely just need to redo something you thought you did properly.... Then move on to zebras only after you've triple checked the obvious...

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