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Old Goat's Boat

R

retired mechanic

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I have a 1982 70 hp johnson with jet pump hanging on my 15 foot ski barge. The &%*) is driveing me crazy. Overhauled carb, swithed fuel tanks, renewed fuel pump, renewed on coil and three sets of plugs, renewed pump up bulb. (It was leaking) Compression good and even. ETC.

Problems range from the complete shut down of one cyl.( not always the same one) to a high speed miss. The last time out, it was missing as I tried to bring rpms up,but pumping the bulb helped me past that. Later that same day as I was tried to return to the dock, I had a steady miss, by choking each cly. individually I was able to determine which cyl was missing and eventually that cyl picked it's self up. (Pumping the bulb had no effect this time) I have cleaned, replaced, and cussed for hours try to make this engine run well every time, or at least have the problems remain the same long enough to determine just what is going on.

I am a mechanic of some 40 years experience so, this is particularly frustrating. Willing to listen.
 
i'm going to ask some "stupid" questions so just bear with me. you stated that pumping the bulb corrected the problem one time. that tells me that you have a fuel delivery problem. have you checked quick disconnect fitting.(i would bypass to eliminate) check or replace ALL fuel lines . a tiny pin hole could cause it to suck air.(happened to me this past weekend). have you changed filters ? as you know , be particularly careful about running it with a leaning condition . if none of this helps , i would go through fuel pump again then carbs. good luck
 
dtoole said:
i'm going to ask some "stupid" questions so just bear with me. you stated that pumping the bulb corrected the problem one time. that tells me that you have a fuel delivery problem. have you checked quick disconnect fitting.(i would bypass to eliminate) check or replace ALL fuel lines . a tiny pin hole could cause it to suck air.(happened to me this past weekend). have you changed filters ? as you know , be particularly careful about running it with a leaning condition . if none of this helps , i would go through fuel pump again then carbs. good luck
Click to expand...
{Yes I have replaced the entire hose assembly, and have thrown away the rest of the lines. There was a rotten hose and I felt is was fixed for good when I threw that hose away and cleaned all three carbs. Does the fuel pump work from a vacum impulse?
 
May I suggest the following.

Remove all electrical plugs and connectors everywhere on the engine, clean with metholated or carb cleaner, let dry and put everything back together with a little electrical grease or similar.

Make sure that the pins, male and female in the multi wire rubber plugs are located within properly.

Pay a lot of attention to the engine electrical ground lugs and bolts. Make sure they are shiny clean all surfaces. Most should have star washers, clean them as well.

Make sure that ignition leads are sound and clean connection either end and they do not touch each other or the motor assy. There should be clips or something that the wires pass thru that insulate and position them accordingly.

The HT cables are original type wire core? Do not use automotive silican leads.

Try that aye?

Regards

B
 
You say... compression is good and even etc. This really doesn't tell us much. Take a deep breath and start from scratch.

Today, or at some soon future time... what exactly are the psi readings of each individual cylinder?

Spark.... with the spark plugs removed, do a spark test as follows. Rig a spark tester whereas you can set a 7/16" gap for the spark to jump. The spark at cranking speed should jump that 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it?

Note that using the spark plugs to check the spark is a total waste of time.

Spark plugs should be Champion QL77JC4 plugs gaped at .040 (you can try the .030 gap later).

(Spark Tester - Home Made)
(J. Reeves)

You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.


Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:




..........X1..........X2


.................X..(grd)


..........X3..........X4

If the above two tests are as they should be, that leaves the fuel section.... Did you manually clean the high speed jets that are located way in back of the float chamber drain plug... in the bottom center portion of the float chamber? If not, do so carefully with a piece of single strand steel wire.

Let us know what you find.
 
sorry folks .. I typed for an hour trying to answer all your questions and the all of a sudden lost every thing. I have to go to work now . will try again later. Retired mechanic. ( that is still working )
 
I tried to do this this morning and lost it all. So I will try again. The first order of business is to say thanks to all of you that have asked questions and posted suggestions. I am a mechanic and all of the posts were legitimate questions and suggestions, and I can relate to them all. Again, thank you all. Once I leave the house in the morning, I do not have computer access until I get home so here goes again. This is where I am right now.
· Spark plugs are Champion L77JC4 gapped @.040. They have been replace twice, just to make sure.
· The spark is a very strong blue flame that looks like a lightning bolt and will easily jump a 5/8 inch gap at cranking speeds.
· The cold compression is 125 pounds on all cyls.
· The fuel pump is new, and as I write this so are all the fuel lines, primer bulb, and hose ends.
· The tank is spotless and there are no detectable air leaks at the fittings. (I pressurized it and used soap)
· The carbs have been cleaned and re-cleaned. Just today I took all three off again and cleaned them, I even took the soft plugs out and ran wire through jets, finishing with compressed air and Berrymans. The floats are set to be parallel with the bowl gasket and drop is ¾ inch. There isn’t enough room here to relate to you all the fuel problems that I have had and explain why I had them, but right now I think I have eliminated everything that is fuel related.
· I am not trying to be evasive or hold anything back. I had the engine running very well except for a little high speed flutter that bothered me ‘cause I didn’t know if I might not have been fighting a lean situation and didn’t want to burn a piston.
· I went looking for that “flutter” and in so doing, recreated some problems that I had once solved, all of them fuel related. I understand what I did wrong and have corrected the situation.
· In the mean time I discovered pieces of rubber in the filter and that is why I threw all the hoses away and re-cleaned the carbs.
· So now, as soon as I can ,which will probably be next week, I am going to put the boat in the river and see what happens. Hopefully, if there is any problem remaining, it will be the high speed miss and then I start checking all of the rest of the things that you folks have so graciously shared with me. Anyway , until I can run it again, I just won’t know. Please feel free to quiz me, but I have to put any more repairs on hold for a few days to work out of town until next week. See you all and thank you. You are truly professionals and you are much appreciated.
 
The rubber electrical plugs that lead from the timer base to the powerpack, pack to plugs, etc... The pins and sockets within them have a habit of being pushed back slightly which results in a not too perfect connection which in turn results in intermittent problems. They also might be slightly corroded or just plain dirty... check them.

Also the wires leading to those pins/sockets have been known to break off right at the pin/socket resulting in a make/break condition, BUT the wire will remain in the rubber plug simply due to the friction/tightness of the plug. That's been known to drive a few people nuts... check that too.

In checking the spark... when doing so, move the timer base from the retard position to the full advance position to check for a internal wire break.

Hint... If your browser has a habit of dropping off the Internet, do all your typing in a self saving editor of some kind, then copy/paste into this site as needed. (been there)
 
Thanks.. I will add the electrical systems checks to my to do list before I run the boat again. It all makes sense, and I have seen exactly the same on automobiles.. Some times I just get too close to the work to think it all through. Take care.
 
retired mechanic said:
Thanks.. I will add the electrical systems checks to my to do list before I run the boat again. It all makes sense, and I have seen exactly the same on automobiles.. Some times I just get too close to the work to think it all through. Take care.
Click to expand...

Agreed.... There are times when I'm working on my vehicles that I can't see the forest for all those damn trees in front of it.
 
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