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77 Evinrude 70 cab problem

S

ship wreck

Contributing Member
I'm having issues with this motor idling in the water. IT idles fine on the muffs but does not want to stay running while in the water. I've been doing a lot of troubleshooting and today I was checking for vacuum leaks with carb cleaner. For good measure I shot a bit down the carbs and on the bottom carb it caused the motor to speed up not slow like it di in the other two carbs. Ok so that carb is lean. It's not dead as because when I pull the plug the engine does change pitch and speed so it is fueling a bit but not enough. To verify I unhooked the chokes so I cold close them individually. On the top and middle carb closing the choke kills the motor. On the bottom carb it causes the motor to smoke a bit but it stays running no matter how long I hold it closed.

I just rebuilt these carbs in the last month which cured my problem of the motor dying when transitioning from idle. The floats, needle and seat were replaced and set per the instructions in the carb kit. I'm not sure what could have happened here but my main concern is knowing won't have the same issue if I go through the carb again. Not much to these carbs and when I "rebuilt" them I did pull all the plugs sprayed out all the passages, blew them out with air and inspected all the passages to make sure they were clear.

Any advise on bench testing or is there something specific to look out for?
 
The bottom carburetor is still fouled. Double check all passageways and make sure that the high speed jet that is located in the bottom center portion of the float chamber (way in back of that 7/17" slotted bolt) is absolutely clean. Fuel must flow thru that jet before it can gain access to any other fuel passageway.
 
This will be the third time through that carb. I rebuilt all 3 last year when I got the boat and then stupidly let the motor sit for 6 months without draining the fuel so I had to go through them all again. The main jet and the idle jet were visibly clear as was every other passage that I could shine a light through. I did use a kit and pulled all the plugs to get at all passages. I have a new fuel pump with a screen type filter in it but it almost seems like there was contamination in the system that settled in the bottom carb. Should I be running an in line filter? The screen in the fuel pump seemed like it would be sufficient as it's pretty fine but maybe not.
 
I pulled it off the carb and blew it out without taking out the core plugs as I didn't have a kit. I captured the fuel and inspected everywhere I could before starting and there was nothing to blow out. I captured all the carb cleaner anyway and it had nothing in it. Put it all back together and I have the same problem. If I cover the carb opening with my hand I feel the suction and my hand gets wetted with fuel but the motor does not stall. Same thing with #1 but I can stall it with the choke. #2 dies almost immediately and has the strongest pull. I'm back to thinking reeds.

Thoughts?
 
Apparently I misread your original post... I had assumed that when you choked the bottom cylinder, the bottom cylinder started firing. After rereading that original post and your latest post, I am of the opinion that when choking the bottom cylinder, it does not start firing but rather does nothing more that have the engine smoke more than usual. However, you did say that when you sprayed a little carburetor cleaner into the bottom carburetor, the engine did speed up a bit... this is a bit confusing.

Note that if you had a reed problem, there would be no suction when you cover the carburetor throat with your hand, nor would the engine be drawing in more fuel (smoking).

Have you checked the compression? What are the individual cylinder readings?

With the spark plugs removed, the spark should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it? Note that the 7/16" gap is important... checking the spark by using the spark plugs is a waste of time.

You can stick a #2 Phillips screwdriver tip into the coil spring lead that normally grabs the spark plug, then hold its shank 7/16" - 1/2" away from the powerhead to approximate that gap.
 
I'm glad an expert is confused as well :) I did a compression check last summer when I got the motor and it was in the 105 range if memory serves but I'll do another one today. I did check spark, that is how the troubleshooting started, but not using a "controlled" spark tester. I pulled each plug wire while idling with a pair of grounded pliers (been lit up too many times so I always ground my pliers now) and the spark ran out of the plug wire and arced to the pliers with a white hot arc. This was preceded by doing DVA voltage checks on the whole system which all checked out good. I have not checked timing yet.

I'll rig up a spark tested so I can do it properly and report back my findings.

Just another piece of information. When I pulled the plug wire from #3 it does change the idle some and the exhaust note changes. When I plug it back in it seems to run better and faster for a short time then the idle drops back down and is a little rough. That made it seem like the cylinder was loading up with fuel to a more correct mix and then leaned back out after running for a bit. This is my first outboard so I'm unsure what rough is so it may be normal. I've been working on four stroke auto engines for 30 years but 2 stroke gas engines are very new to me.
 
Checked compression and I'm at 115,110,110 #1,#2,#3. Spark is good can easily jump a 7/16ths or bigger gap using a screw driver in the plug wire. The only issue is #2 and #3 leak out the top of the plug wire in certain conditions. Upon inspection I can see a chalky area where it's allowed to leak. With everything plugged in and the cover off it's not leaking.

I've linked to a video on you tube that shows what it's doing. I choke each cylinder as well as pull each plug wire. I took this with a crappy phone and was working by myself so the video quality is not great but hopefully it gives more insight.

http://www.youtube.com/watch?v=9gQKmIijlKQ&feature=youtu.be
 
more fussing with motor tonight. I'm at a loss so I'm moving parts around to see if I can get the trouble to follow. I've swapped the plugs on #3 and #2 with no effect. I then swapped the coils with no affect. Tomorrow I'll be swapping #1 and #3 carb as #2 requires a bit more finagling to swap. If the trouble does not follow then I must have an internal problem and I'm at a loss as to what could be going on or what to check next.
 
I was talking to a friend about this problem and he said "looks like #2 is doing all the work". That made me think of the Goldwing I had that had four carbs. To balance that motor I used a manometer hooked up to each cylinder and adjusted till the vacuum was equal at idle. That's not possible with this motor so I decided to use the choke test. I "resynced" the carbs by the book and the problem seems to get better. #3 (bottom) still would not kill the motor but had a bigger affect when chocked. I took it one step further and slightly cracked #1 and #3 then tightened down the linkage and now all three cylinders have the same affect when choked. Idling on the muffs at 1000 each cylinder when choked causes the motor to load up a bit and slow down but none kill the motor completely. This seems balanced to me.

I need to set the timing and the throttle linkage and then lake check it.
 
The only issue is #2 and #3 leak out the top of the plug wire in certain conditions. Upon inspection I can see a chalky area where it's allowed to leak.
Click to expand...
I would replace all spark plug wires.
 
guyjg said:
I would replace all spark plug wires.
Click to expand...
Yes that is good advise the only rub is that at 55 bucks a piece that's a bit spendy. Unfortunately on this motor the plug wire is part of the coil. Now that said I could do the generic coils that have a separate plug wire which is almost half the cost and provides the ability to change the wires but I'll never need to do that in my lifetime so the advantage is cost.

I do see boots available but not sure how I would replace those without damaging the wire. I have a parts motor but the powerhead is a 74 with factory coils that are slightly different. One is bad so I can't swap them all in and I'm hesitant to use just one or two.
 
The "boot" assemblies are available at any dealership.

The "plug wires" are available at any automotive parts store, usually in any length you want so you can cut your own. Be sure to get the wires that have a metal inner wire (NOT CARBON).

The plug wires simply unscrew from a spiral prong within the coil and can be replaced easily. There is no need to replace the entire coil assembly.

(Replacing Regular Spark Plug Wires)
(J. Reeves)


If you also need the spark plug boots and the spring terminals that connect to the spark plugs, purchase them from your local dealership (OMC Part #581027). This includes one boot and one spring connector. Price is about $3.25ea.


Purchase whatever amount of spark plug wire you need. Be sure to purchase the kind that has a steel twisted wire leading through the center of it....... not the carbon type plug wire that many automobiles now use.


Using your old plug wire, cut the new wire to a length about 3/4" to 1" longer. If you have no old plug wire, just make sure that the wire is longer than you'll need as you can trim the other end later.


The rubber boot, spark plug end.... With the wire cut to the length required, trim back 1/4" insulation again but do not solder tint the wires. Simply fan out the wires and fold them back against the insulation, cutting the excess off as explained above. Holding the spring wire terminal, estimate where the prong should be inserted so that the spring will be flush against the exposed wire. Hold the spring terminal away from the wires end (sideways) and insert the prong into the insulation and into the center wire, then swing the spring terminal in front of the exposed wire portion (makes a tight fit for continuity purposes).


Spraying the inner portion of the boot where the wire will insert with a small amount of WD40 makes the installation of the wire a easy project. That's it.... you're done.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
 
UPDATE
File under "KISS"

The carbs were definitely out of sync but the "extra crack" I gave #1 and #3 was unnecessary. Part of my issue was throttle adjustment. I did not have the throttle cable adjusted properly which in turn was causing timing at idle to be too far retarded. After resetting that I found the idle to be too high and so I took that "extra crack" out of the two carbs and performed a "choke test". All 3 cylinders behaved the same slowly killing the motor if left them choked. I verified the timing pointer was correct and checked timing at idle which is spot on. I followed Joe's instructions on setting WOT Timing which is also spot on. I should have gone through the basics first and I would have solved my issue days ago.

Wanted to update the thread so if some one found this in the future they had the whole story. Gunna lake test it on Sunday but I'm pretty confident I have the issue solved.
 
So had the boat out today. Started off good everything was running fine. Got to our anchorage and had to keep resetting the anchor. This was more difficult than it should have been because the motor was back to it's old tricks of not wanting to idle in gear. It would, but after a while idling in gear (typically while backing) the motor would just die. Idling, or just over idle, in forward was ok as I had no issue with stalling putting though the no wake zone to and from our anchorage.

Coming back across the lake everything was fine then the motor slowed and died. Acted like it was out of fuel but there was 1/3 of a tank (5 gal) and the vent was open. I messed with is trying a bunch of different stuff and noticed when I could get the motor to at least idle the bulb was going flat. After playing around for a while I finally pumped the bulb till it was hard with the motor off and that cured the problem. I cruised back to the ramp at WOT with no issue.

I think this motor is possessed.
 
Having the primer bulb to be drawn flat indicates a fuel restriction.... faulty valve at the bulb or most likely the following.

(Fuel Anti Siphon Valve)
(J. Reeves)

Many of the later OMC V/6 engines incorporate a fuel restriction warning via a vacuum device attached to the powerhead. If the engine overheats, or if you have a fuel restriction, the warning is the same.... a steady constant beep.

NOTE... Only the V/6 & V/8 engines have the above "Fuel Restriction Warning". The warning horn will not sound on the other models.

The fact that a engine is not overheating, but the warning horn sounds off with a constant steady beep, and that the rpms drop drastically would indicate that the engine is starving for fuel due to a fuel restriction. Check the built in fuel tank where the rubber fuel line attaches to the tank fitting. That fitting is in all probability a "Anti Siphon" valve which is notorious for sticking in a semi closed position. It will be aluminum, about 2" long, and the insides of it will consist of a spring, a ball, and a ball seat. If this valve exists, remove it, knock out those inner components which will convert it to a straight through fitting, then re-install it. Hopefully that cures the problem.

The above procedure will cure a restriction problem with the anti siphon valve as stated. BUT, it may also allow fuel to drain backwards to the fuel tank when the engine is not running (siphoning backwards) due to the fact that the carburetors/fuel pump etc are higher than the fuel tank. This condition is not an absolute as the valves in the fuel primer bulb usually prevent this backwards siphoning problem. However.... if this does take place, the cure would be to install a new anti siphon valve.

NOTE: There has been cases when the output valve in the fuel primer bulb would come apart, and the inner portion of the valve would actually reverse itself and be drawn back into the primer bulb's output valve body. This in effect would create a shut off valve and result in a fuel restriction. If this is the case, you should be able to feel something laying in the bottom of the primer bulb when held horizontally.
 
I don't believe I have an anti-siphon valve but I'll look again. The tank is sitting next to and at the same level as the engine so the anti-siphon is unnecessary. The odd thing is it lost fuel pressure suddenly then recovered suddenly. There is nothing in the tank, I inspected the insides before putting it on the boat, so either my fuel line is deteriorating or I do have that anti-siphon valve and it's failing. I have a new primer bulb so I'll install that just for good measure.

Thanks
 
The anti siphon valve pertains to a built in fuel tank. If using a portable tank, there is no anti siphon valve. A primer bulb in your case would be due to a flawed primer bulb valve or a closed tank vent.
 
Well this is not a portable tank in the strictest sense but it's also not built in. It's a ,currently, deck mounted steel tank that has an always open vent (thinking about changing that). The suction connection seemed to be an elbow and small "nipple" that was not OTS pipe fittings from the hardware store but thought it was just straight through pipe. I'm gunna take it all apart tonight and see what's what. I'll also pull the bulb off, cut it open, and see if anything came apart. I assumed that the bulb should go rock hard when pumped and this one does not although it does pressurize the fuel system. Could that be a tell that there is an issue with the valving? Doesn't really matter as I'm going to change the bulb but it's good to know for the future.


Maybe I dropped something in the tank unknowingly and it got caught up in the pickup. A bulb that leaks back to the tank would be helpful in this instance as it would tend to clear the obstruction. Thank-fully I have a fuel can big enough to empty the tank into.
 
Re: 77 Evinrude 70 carb problem

I did a number of things tonight so if it's fixed unfortunately I have no idea what fixed it.

I pulled the pickup out and found that there is no anti-siphon system as Joe had expected. The pickup however was roughly 3/16ths off the bottom of the tank. This tank design is very simplistic as there should be a small sump but there is not so to enable the tank to be sucked down as far as possible the pickup is very close to the floor, too close for my liking.

This is what I did,

I shortened the pickup so I have about 3/8" clearance with the screen installed. While measuring the depth with a piece of threaded rod I pulled a small piece of trash out of the tank. It was some sort of fibrous material and I am concerned there is more in the tank. Since it's not practical to remove the tank right now I pulled the screen off the pickup and added a fuel filter at the tank outlet. I then shortened the fuel line so it was only as long as needed (it was about 2 feet too long) and added the new primer bulb fairly close to the engine. I'll carry a spare filter with me and there is not much chance of anything clogging the pick up tube as it is huge but even so I can get it out pretty easily if needed. Removing the entire tank is a bit more complicated.

So we'll see if this fixes the issue. I'm a little concerned that the fuel pressure is low so I need to get a "t" installed in the discharge from the pump so I can check it. This really has nothing to do with this latest issue but I did not entirely solve the poor idle issue (although it is better) so I want to check the fuel pressure.
 
Re: 77 Evinrude 70 carb problem

Took the boat out today and it ran fine for the most part. The motor is still finicky. Occasionally it will stall when transitioning from idle to part throttle in reverse. I have a new prop for it and it ran well at WOT all day (we burned 9 gallons when a typical trip burns 3) until the trip back across the lake at the end of the day. We were running fine up at 4900 RPM when the motor acted like it was running out of gas. Three pumps of the bulb fixed the issue and it did not reoccur. This boat is possessed but at least the idiosyncrasies are manageable.
 
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