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Evinrude Big Twin: runs on choke only

D

dh_user

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[FONT=&quot]Hi all - continuing the post here: [/FONT]http://www.marineengine.com/boat-fo...anifold-(was-Big-Twin-flywheel-compatibility)[FONT=&quot]

I finally got a 58-year-old engine running yesterday. I have to admit, it felt pretty good. I let it run in neutral at idle for 20-30 minutes and then tried to open the choke... it died. Several more tries, with the same result. I'll post a short video from my phone.[/FONT]

[FONT=&quot]Here's a list of what I've done (1961 Evinrude 40hp, model 35524). All replaced/rebuilt parts are either NOS OMC or brand-new BRP.[/FONT]
[FONT=&quot]. Removed, disassembled, cleaned, and reassembled every part from the powerhead up[/FONT]
[FONT=&quot]. Replaced broken crankshaft, installed new omc spaghetti seal and crankshaft seals[/FONT]
[FONT=&quot]. Replaced every gasket on the engine with omc gaskets, sealing with either Permatex 3 or 3M 847 per Joe Reeves' articles (note: no seal on 2 intake gaskets or carb gasket)[/FONT]
[FONT=&quot]. Torqued every bolt to spec in the condensed service manual (where listed); sealed bolts with either Permatex 3 or aluminum anti-seize[/FONT]
[FONT=&quot]. Replaced thermostat and gasket[/FONT]
[FONT=&quot]. Rebuilt fuel pump and sediment bowl[/FONT]
[FONT=&quot]. Rebuilt vacuum cut-out switch[/FONT]
[FONT=&quot]. Replaced all ignition components (condenser, point, coil, ignition wire, boot, plug)[/FONT]
[FONT=&quot]. Replaced all fuel, vacuum, and hot water lines[/FONT]
[FONT=&quot]. Rebuilt hot-water choke and carburetor (including seat/needle valve and both plugs)[/FONT]

[FONT=&quot]Since choke-only operation usually means fuel delivery, I pulled off the carburetor again to run all the checks I know how to do. Here is what I did.[/FONT]
[FONT=&quot]. Remove the inbound fuel line (supply from pump to carb), blow on the line, fuel blows out and then air passes through the carburetor[/FONT]
[FONT=&quot]. Remove carburetor from intake manifold, turn carb upside down, blow on the inbound fuel line, air does not pass[/FONT]
[FONT=&quot]. Remove the bowl, check (new oem) gasket for any tears, etc.[/FONT]
[FONT=&quot]. Check the float (level to carb body)[/FONT]
[FONT=&quot]. Confirm seat needle isn't stuck, and float moves freely without any noise or sticking[/FONT]
[FONT=&quot]. Remove float/spring/seat/jet; inspect; look for dirt or debris; spray each part with carb cleaner, spray with compressed air to check all the holes are open[/FONT]
[FONT=&quot]. Confirm idle circuit and high speed circuit are free, using compressed air, spraying both both ways[/FONT]
[FONT=&quot]. Reassemble the carburetor[/FONT]
[FONT=&quot]. Re-check the float/needle/seat by blowing into the fuel line (right side up, air passes; upside down, no air passes)[/FONT]
[FONT=&quot]. Install[/FONT]
[FONT=&quot]. Verified idle adjustment valve is backed off a soft seated position by 1-1/2 turns (tried 1 turn and 1-1/4 turns as well; no difference in the outcome)[/FONT]

[FONT=&quot]This last time, I also removed the fuel pump, checked for dirt/debris, sprayed carb cleaner/compressed air, checked the sediment bowl and gaskets, etc. There was a little dirt in the glass bowl (very little), so I cleaned it out.[/FONT]
 
[FONT=&quot]So the punch line: I don't think this is the carb. I've checked the fuel tank / vent / bulb / line. I use this same setup for my 15hp 70s Johnson, and it works great. Just to be sure, I dumped the last gallon or so of fuel on a burn pile and used brand new gas and oil.[/FONT]

[FONT=&quot]Things I'm wondering about:[/FONT]
[FONT=&quot]. Carb float: looks like it's cork (sort of a wheat/yellow color, not red) and not plastic. It's a brand new BRP kit that's listed for this engine (439074) - but should I research a same-size plastic float and replace it?[/FONT]
[FONT=&quot]. Potential vacuum leak in carb: I did make a mistake when cleaning / soaking this carb. I pulled everything apart (removed all non-metal pieces) , dropped in the Berryman container, and left it in there for 2-3 months while I got sidetracked with another project. Any possibility I damaged it? The fluid was extra dirty when I removed the carb, so I used the ultrasonic cleaner as well (3 parts water, 1 part Simple Green). Carb looks nice and clean, and nothing suspect... just not sure if I could have done damage in some way without realizing or being able to see it.[/FONT]
[FONT=&quot]. Potential vacuum leak in crankcase: I have no reason to believe this is true; just read and saw threads on this, so I sprayed the top crank seal and the joint where the crankcase halves come together with soapy water while pressurizing the cylinders and turning the shaft... no bubbles. Any other ways of testing this? Or any reason to worry about it?[/FONT]
[FONT=&quot]. Potential vacuum leak in manifold: I didn't seal the manifold to reed plate or reed plate to block gaskets (consistent with many threads and some direct answers I got to my question on the other thread). Given the gaskets are new and there's no sign of damage on any of the metal surfaces (I went back to my photos), I don't think this is it... just wondering if anyone has suggestions to definitive tests to eliminate this as a possibility.[/FONT]
[FONT=&quot]. Timing (now I'm starting to doubt that again): points open when flywheel mark / timing tool mark enters the 2-mark gap on the magneto cam plate. Position of the magneto: I had the magneto fully retarded when doing this adjustment. Is this correct? Alternative positions that I think I remember using on other engines: "pickup point" position (magneto cam scribe mark is even with the intake manifold sync point); or fully advanced magneto (in forward gear, "WOT" timing setting).[/FONT]

[FONT=&quot]Appreciate any direct experience anyone may have on this. We're so close with this one! Thanks in advance.[/FONT]
 
[FONT=&quot]I should add (until I get my video posted)... here's what the video shows.[/FONT]
[FONT=&quot]. Choke is between "Manual" and "Auto"... about 1/8" toward "Manual" from the "Auto" dimple... just enough to keep the hot water and vacuum from opening the butterfly, but not 100% closed.[/FONT]
[FONT=&quot]. At this choke setting, and the throttle set to "Start," the engine starts every time. I have the idle stop set a little high... about 1/2 way between "Start" and "Slow"[/FONT]
[FONT=&quot]. After starting, the throttle adjusts to the idle stop, and it will run there without any feathering or rescuing (I've left it for 10-20 minutes at a time).[/FONT]
[FONT=&quot]. When I move the choke to "Auto" the engine picks up rpm for somewhere between 2-3 seconds and dies. Every time, no exceptions, doesn't matter if the engine is cold or hot.[/FONT]
[FONT=&quot]. When I move the choke to "Off" the engine seems to maintain rpm (maybe a slight increase but not like when I move it to "Auto") and dies within 2-3 seconds.[/FONT]
[FONT=&quot]. When I move the choke all the way to "Manual" it just dies (no increased rpm)[/FONT]
[FONT=&quot]. Pumping the fuel line bulb doesn't have any effect[/FONT]
 
Timguy, thanks for the suggestion. Someone else asked the same question, so I'm gonna try it and see. I'll also verify the new packing washers are fully compressed in there, and then run the idle mix needle from 1 turn out to 4 and see if that changes anything before rebuilding the carb a second time.
 
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