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Mercruiser IO 140

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genesis

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"I have a late 70's mercru

"I have a late 70's mercruiser I/O 140 that has given me trouble over the last two year. after the engine has been run for about ten minutes, it wont accelerate. it hovers around 1200rpms and sounds like it wants to go but seems like it is just not in time. The Kicker... I replaced the spark plugs, wires, rotor and cap, and set the timing and dwell to factory specs so everything on the electronics side as far as I know is in perfect condition. So I am being led to believe it is a fuel issue. It is carburated and I am not knowledgable in those. I did adjust the automatic choke last year a little but not too much. am I being led to believe that i need to rebuild the carb or is the transfer pump failing????? any help would be great."
 
Put a timing light on it when

Put a timing light on it when it behaves poorly. Look under the distributor plate holding the points and condenser to see if the advance weights are rusted and the springs are broken.
 
"Looked under the distributor

"Looked under the distributor plate and found NO broken springs. there is some minor surface residue covering everything, very very little rust. will have to get it out on the water today to get the timing light on it. One thing I forgot to mention is that the battery I am using in the boat is shot. it barely has enough power to start the boat and the boat only start once you let off the key and the starter quits pulling amperage. could this simply be just a replacement battery issue. I do have batteries coming justh aven't arrived yet. Will get out on the water today to check timing."
 
"One thing I forgot to men

"One thing I forgot to mention is that the battery I am using in the boat is shot."

If it will crank the engine there should be enough current to start the engine at which time the alternator takes over. A new battery will make a difference if the old one drops below 10 vdc. Just like jumping a dead battery. Try using a battery charger/starter.

Spray the dist. weights w/WD-40 and move them B/F to loosen them.
 
"Got the boat out on the water

"Got the boat out on the water. Found that I had no spark in cylinder number three. Tried the spark plug on a different wire and it fired, tried a different wire in the number three spark position on distributor got spark. Did the new cap I got come to me cracked? Will spray the wieghts with some wd-40 and until the battery comes I wil try hooking up two batteries in parralel for the amps."
 
""...tried a different wir

""...tried a different wire in the number three spark position on distributor got spark. Did the new cap I got come to me cracked?"

NOOOO! You just proved you have a bad wire.

"I wil try hooking up two batteries in parralel for the amps."

That is not a good idea when one battery is known to be on its last leg. You are dealing w/high amperage there. Why take unnecessary chances.
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"Got spark back to all cylinde

"Got spark back to all cylinders and sprayed the springs and weights down with wd-40. same problem is still occuring. got a timing ligh on it while it was acting up and found it to be about 8 degrees. I think that that is pretty close to what the specs are. engine does now however run harder at idle, not just under throttle. It still does however not want to go even when under full throttle. I did give it the gas and after about two minutes of chugging along the engine must have "caught up" cause the engine and boat took off but as soon as I slowed down the problem continued."
 
"If its a rochester 2bbl carb,

"If its a rochester 2bbl carb, pull the top of the carb of and look down into the float bowl and check for water beads. I had similar problems, and thats what it turned uot to be. unfortunately I had a bad tank of gas because the carb kept filling back with water"
 
I am working on resetting all

I am working on resetting all the gaps breaker point gaps and will time it when I get it back in the water. If I still have the problem I will look at the carb. Pretty sure its a rochester assuming that the rochester has GM stamped on the top. It is a two barrel. I just don't have a replacement gasket for it and I am trying to to avoid another half hour trip to the parts store.
 
"Sorry guys, had no internet t

"Sorry guys, had no internet the last few days. have worked on the boat though. I once again went through and reset all gaps and replaced the spark plugs. Got it to run perfectly by doing that, so I don't know why it worked all of a sudden the third go around. Also found that the screw holding the automatic choke on were loose. while boating, the choke almost fell off and with the choke loose like that, it gave me the same problem. But I put it all together and is running like a champ. Thanks for all your help. after two years of figuring it out myself, two days here is a much better choice. Thanks again to all."
 
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