lower cylinder not working.... now what?

[foresterjohn]

1993 70hp Evinrude. Lower cylinder stopped working. Died on me in the lake, whole boat shook so i limped back into dock on 2. Runs rough in driveway on muffs but i can hear a tap every 2 seconds while idling.

What i have tried so far (thank you iboats forum!!):
1. New spark plugs - no change
2. switched spark plug cables - no change
2. switched ignition coil with good cylinder - no change

So is next step to replace head gasket? and peak inside? or do i go to the powerpack next?

 

[asdasc]

Re: lower cylinder not working.... now what?

I wouldn't try to run it. I would get a compression checker and compare compression on each cyl. If they are all within about 10% of each other, that is good news, then I would check the spark with a spark gap tester. You should see a good blue spark jump a quarter inch.

That will tell you a lot about what to do next.

Good luck.

 

[foresterjohn]

Re: lower cylinder not working.... now what?

Couldnt get to the parts store for compression checker but pulled the air filter and exposed the carb intakes. if i block either of the top two intakes it stalls out. block the lower and i dont get a reduced response and a bit of fuel comes out. Makes me think it not hitting on much. Also hearing that reapeated tapping.

But the BEST part is that when i looked past the butterfly valves this is what i saw:

2 of the bolts from the air intake cover sitting in the intake!!!. I wondered why I had 6 holes and 4 bolts. WTF? I removed them and replaced the cover. It didn't entirely cure my problem but it helped a bit. Guess I need to do the compression test. Boats are awesome!!

 

[larryg]

Re: lower cylinder not working.... now what?

u might take the intake manifold off and see if the reeds got damaged.had same problem but on a 25,reed was damaged.and lower cylinder wasnt firing.

 

[foresterjohn]

Re: lower cylinder not working.... now what?

Thanks! I'm not the only one!

how do i check if reeds are ok without removing entire manifold? can i? and what do i look for to determine if the reed is ok or not?

 

[DJ]

Re: lower cylinder not working.... now what?

Thanks! I'm not the only one!

how do i check if reeds are ok without removing entire manifold? can i? and what do i look for to determine if the reed is ok or not?

All you can do is look through the throat.

Do the compression check. An auto parts store will rent you a comp. tester.

 

[Joe Reeves]

Re: lower cylinder not working.... now what?

I have a problem understanding how two retaining bolts from a carburetor face plate could find their way into the intake manifold, other than an intentional placement of them there. Who was the last one that had the face plate off to do carburetor work or whatever?

If anything else might have been laying in that reed plate assembly, which eventually traveled thru the reed plate, that would resulted in damage to the related piston and cylinder wall. Frankly, I'd be removing that intake manifold and also the cylinder head rather than to assume this or that.

 

[foresterjohn]

Re: lower cylinder not working.... now what?

UPDATE:
Went to auto zone, got spark tester and compression tester. I got 90 lbs on all 3 cylinders!! (I actually did a little dance!!) and good spark on all three at 7/16". So i am headed to the carbeurator. I am guessing i have a fuel issue on the lower carb. Am i headed in the right direction?

FYI: Thank you to the help on this site. You are all wise and generous with your wisedom!

 

[foresterjohn]

Re: lower cylinder not working.... now what?

ok, now i am worried that 90 is too low and maybe the comp check stinks......

 

[foresterjohn]

Re: lower cylinder not working.... now what?

rechecked compression and got 110 on all three. let it turn over a bit longer. pulled the lower carb. looks clean. time to put it back together and see what i got. if something doesnt change this time then i am going to lose it.

 

[mrcrabs]

Re: lower cylinder not working.... now what?

I had nearly the same thing happen on my 1975 70hp, only one screw got lose and wedged into the reed, I bought it that way....only way I knew something was wrong is that it spit gas from the lower carb....I put blue locktite on them. I understand the problem can be caused by a unbalanced prop, also have been told a unbalanced prop can losen up the starter bolts on a 3 cylinder looper.

 

[patrick4266]

Re: lower cylinder not working.... now what?

You better do what Joe Reeves said and pull that head and intake. With the history you just told us that tap might very well be a bolt or piece of boat in a cylinder. Now is not the time to hope for the best, you have to assume the worst. Do what Joe says are there's a good chance your going to blow it up.

 

[boobie]

Re: lower cylinder not working.... now what?

Before tearing into it, start it up on the muffs and see if you can still hear the tapping.

 

[foresterjohn]

Re: lower cylinder not working.... now what?

start it, dont start it....what to do.

For what its worth, i think the tapping was part of the cylinder misfiring. and the two bolts wer recovered. so i am down to 3 things.

1. carb or fuel issue still
2. reed valves
3. head gasket (but doubtful given decent comprression)

 

[mrcrabs]

Re: lower cylinder not working.... now what?

how many bolts were missing from the air silencer, just the two?

 

[foresterjohn]

Re: lower cylinder not working.... now what?

yes 2 bolts. and those were recovered in the intake. so i shouldnt have anything in the cylinder.

 

[boobie]

Re: lower cylinder not working.... now what?

The only way you'll ever know what is going on is to try and run it.