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Not firing on bottom 2

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nicknack2

Regular Contributor
"Here we go again... I put new

"Here we go again... I put new carbs on my mercury 1150 early 70'ish model and I have not been able to get it to go on gear because it dies, well today I re-checked my "Sync" and all checked good, but still died when put on gear, I checked for spark on each wire which I have, so I have spark but no fire on 5 and 6, compression ~115-120 on the 1st five, I was unable to put gauge on 6 because I can't fit the hose/fitting in to the sparkplug hole, but I can feel good pressure when crank and put my thumb on it.

any ideas or checks you guys can tell me to do??"
 
Were these carburetors really

Were these carburetors really " new " or some used I will try it type.Nothing goes wrong with outboard carburetors only dirt / gum keeps them from working properly.In 40 years I have never run into a " if I put a new carburetor on it will run " situation. So why did you change the carburetors???
 
"Well I didn't want to bor

"Well I didn't want to bore everybody with a long story but here is, I bought a boat, the tank had old gas and water, I ran the motors(twin mercs 115) and ran like crap, well after I found out about the water and bad fuel I decided to rebuild the carbs (which were leaking after pumping the fuel bulb… bad needless and seats), I did the first engine and while taking the carbs apart I had to stop, every part inside of the carbs was frozen in place it appears as if "they"(who ever rebuilt them before) used red lock tie and all the brass parts, actually all the parts were just striping so I called Wayne Canino who told me he could sell me a set of re-built carbs and I went ahead and bought them, that is why I swapped carbs before that the motor would run in gear and actually rev in gear to high 4000 RPM before staring to miss due to sour fuel and water. But now when it goes in gear it dies due to the non firing cylinders"
 
OK now we know-----your plug w

OK now we know-----your plug wires are hooked up / marked correctly on the bottom 2 cylinders???The distributor cap will have the #'s marked 1-6
 
"yeah, wires are fine and in t

"yeah, wires are fine and in their correct location, spark jumps good with a nice blue color..."
 
"So you have no fuel at #5 and

"So you have no fuel at #5 and #6 , it is the only thing left.You say the carburetor is rebuilt / new.So how are the reed valves / lower reed block???????"
 
"Nicknack, What do the spark p

"Nicknack, What do the spark plugs on #5 and #6 look like? Are they wet with fuel, wet with water, dry or do they look like new (Steam cleaned). If they are wet with fuel, the fuel pump diaghram may be leaking. If they are wet with water or steam cleaned, the exhaust cover or baffle may be leaking or holy.

Also make sure the plug wires are not arcing to ground.

if they are dry, the float may be stuck closed on the bottom carb."
 
"IKEA: So how are the reed val

"IKEA: So how are the reed valves / lower reed block???????

how do you check the reeds???

if I have compression the reeds should be working as they should right???

Cris1956: if they are dry, the float may be stuck closed on the bottom carb.

thats what I'll check today..."
 
REED VALVES HAVE NOTHING TO DO

REED VALVES HAVE NOTHING TO DO WITH CYLINDER COMPRESSION-------and you can take that to the bank.--------When cylinder compression occurs the reed valves should be open.If they are open all the time you will have problems with that particular cylinder. The water that messed up your carburetors may have done more internal engine damage.
 
"Thanks Ikia… So, the internal

"Thanks Ikia… So, the internal damage is not in the cylinder area...at least I got good compression... Today I took the carburetor apart (at least the bowl area) it appears as it the needle was sticking, replaced the needle and seat, the screen/filter and respective gaskets, but did not fixed the problem. Went ahead and crank the motor, got it running and screw in the idle screw all the way in with zero response (the 3rd carburetor the one for 5 and 6 cylinders), again took the spark plug wires off on both 5 and 6 with no response engine keep running w/o incident, I did try that for all other spark plug wires (1, 2, 3, 4 cylinders) and as soon as the wire came off the engine bogged down.
I also took the spark plugs off on 5 and 6 to check for water intrusion, but was not able to tell…the plugs were wet, but it seem to be a gas/oil mixture, how can I tell if water is getting in to the combustion chambers???
Also I guess reeds are my next step… Any ideas on how check them??? I don’t want to give up on my motors, I feel that they still got life in them, but they are also taking lots of my free time…
Ohh one more thing I tried... I sprayed a 1/50 mix of gas/oil(two stoke of course) directly in to the throat of carburetor # 3 and the motor did not responded at all..."
 
I would be removing the bottom

I would be removing the bottom carburetor and then looking in there ( with a small mirror ) to see what shape the reeds and the reed block is in.
 
"And what is it that I'm l

"And what is it that I'm looking for? (I know damage but specifics...)If I need to replace the reeds, I would have to take the motor completely apart right?"
 
"Hi there,

Not too familiar

"Hi there,

Not too familiar with this motor, but worth looking into, maybe?

Can you interchange the carbs and reeds from another intake? IE the top set and swap with the bottom set?

If so, do the carbs first, then the reeds. You'll eliminate one culprit at a time. Takes time, but might save you some cash.

If the problem moves with the suspect parts, you know where to start spending.


Hope this helps?

Cheers!


Benjamin."
 
I suspect the bottom two pisto

I suspect the bottom two pistons are shot. Compression or not. These motors don't like wear and tear in the bores. The vacuum signal from behind the pistons disappears right away. Hence it will not pull gas at idle any more.
The reeds are internal and if the gas is not blowing back then they are fine..
 
"As bandit said.. the reeds ar

"As bandit said.. the reeds are internal and the motor has to be taken appart in order to replace the reeds.
Question for Bandit... what signal are you talking about?, worn bores equals low compression, but I do have compression in the 115-120s, Im no exacly sure what you mean by vacuum signal, are there some sensors???
Im going to crank the engine over and put my hand on the carb and see if is blowing back... as soon as I get a chance."
 
"The cranckase pressure/pulse.

"The cranckase pressure/pulse. I have had many of these engines do this. There will not be enough vacuum on the carb base to pull the gas into the motor anymore. Or any transfer pressure to push the gas out in front of the piston. The compression might still be o.k. but there is no gas in the cylinder to compress.

Block the front of the carb with your hand, there should be a good steady vacuum pull there.

Too much blowby past the rings, is what I am trying to say. You can always make compression like that, but not the needed vacuum to get the gas out of the carb."
 
"bandit I put my hand over the

"bandit I put my hand over the carb and I can feel sucktion I notice water coming out of the exhaust port in the shaft is that means water intrusion??
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