79' 70hp merc dies when i put it in gear

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hwft

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put it in the shop to get the carbs rebuilt and they found that the #3 cylinder only had 45lbs of compresion. they told me that was causing it to die under a load so i put a new piston and rings in that cylinder and new rings in the other two. i also rebuilt the carbs,put new fuel pump and all new hoses and it still dies when i put it in gear. it runs good at an idle with a slight vibration. could this be the timing?
 
JB

JB

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Re: 79' 70hp merc dies when i put it in gear

Howdy, HWFT.<br />Sounds like you were running on less than 3 cylinders. . . . and still are.<br /><br />Running "good" at idle is the biggest fake since Hitler applied for Sainthood.<br /><br />Take it back to the guys who "fixed" it and tell them to fix it right or get a lawyer.<br /><br />Good luck. :)
 
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hwft

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Re: 79' 70hp merc dies when i put it in gear

thanks jb. i am sure it is running on all three cylinders. i grounded them out individually and they are all firing. the guy i got the motor from said that this has been a problem for some time and he has had work done to it and it never fixed it. i did the ring job myself and put everything back the way it was set before. i was thinking if the timing was off that might be what caused it to burn those rings in the #3. any more thoughts on this?...thank you...ps out of the water i can put it in gear when it is running and it does fine. in the water it will bogg and die then i have to choke it to death to get it started again...thanks
 
JB

JB

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Re: 79' 70hp merc dies when i put it in gear

Hmm. More information can really make one look silly once in a while.<br /><br />From what you are telling us now, I agree that it could be a timing or "link 'n' synch" issue.<br /><br />Because you had it apart, I assume that you have confirmed that the flywheel key is sound and that the flywheel is correctly timed to the crank.<br /><br />Double check that, and your linkage and synchronization adjustments.<br /><br />Since choking it heavily is necessary to get off the line, it still sounds like a fuel issue to me, but it seems that you have done all of the right things to that system.<br /><br />Is the choking only required when cold, or even when hot?
 
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hwft

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Re: 79' 70hp merc dies when i put it in gear

jb, sorry for the lack of info. i was told to try tapping the choke when it goes to die and that would help to pinpoint a fuel problem. when i do that it does not pick back up. as far as the choking, if i am running it out of the water and i turn the motor off it will start right back up, if i put it in the water and it dies on me after putting it in gear, thats when i have to choke it a lot to get it to start again. when i took the flywheel off i put the #1 at tdc and scribed the flywheel and the motor and then lined it up when i put it back on. not sure how the timing works on these motors. :confused:
 
JB

JB

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Re: 79' 70hp merc dies when i put it in gear

Howdy again.<br /><br />Try the linkage idle adjustment and ignition synchronization procedure from your manual. <br /><br />I am a bit confused by your description of timing the flywheel. Isn't it fixed by a woodruff key? :)
 
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hwft

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Re: 79' 70hp merc dies when i put it in gear

jb, well i think you were right to start with. i had a guy come over and help me adjust everything. i got it to where it is running but the bottom cylinder is cutting out. it takes off with plenty of power and then you can feel it drop off and then pick back up. i know it is that cylinder because the two top plugs are real clean and the bottom one is oilly. witch is more likly the spark breaking down or the fuel loading up? and is there a way i can check it to know? thanks for the help i am almost there! :)
 
JB

JB

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Re: 79' 70hp merc dies when i put it in gear

AHA! Now you are getting there. :D <br /><br />Swap the coil and plug from the bottom cylinder with another and see if the problem follows it.<br /><br />If the problem stays with the bottom cylinder, see what happens if you squirt a bit of fuel mix into the bottom carb. If that picks it up, redo the carb with microscopic attention.<br /><br />Whether it is carb related or ignition related, I think the cause of your original breakdown is trying to take out #3 again, which means that whatever you have done has only repaired symptoms.<br /><br />It could be in the ignition system, or it could be in that bottom carb. I am more suspicious of the carb right now.<br /><br />Let us know what you find. :)
 
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petryshyn

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Re: 79' 70hp merc dies when i put it in gear

Power packs are known to give trouble on these engines. Losing a cylinder intermitently is not uncommon for these defective packs.....Be sure you have spark on all cylinders.
 
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hwft

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Re: 79' 70hp merc dies when i put it in gear

jb, well i ruled out the coils and wires. i changed them around like you suggested. i also squirted the fuel into the bottom carb and that didnt help. i went ahead and took the carb back apart and went through it again. there is not a whole lot to those carbs. i made sure all the passages were clear, checked the float setting and cleaned the jets. if the fuel is good and the coil and wires are good what is left? he mentioned the powerpack. i have spark to that cylinder it is just missing. when i say missing i mean it will fire for a few seconds and then stop for a little bit and then start again until it loads up so much that it wont fire at all. what could make the spark start and stop like that? thanks...mike
 
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Trent

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Re: 79' 70hp merc dies when i put it in gear

Powerpacs can do the same problem as you have described; As Schematic has already said.
 
JB

JB

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Re: 79' 70hp merc dies when i put it in gear

Okay. Seems that you have eliminated almost everything except the powerpak. Like Scematic and Trent said.<br /><br />I guess I was misled by the history of that cylinder. Usually loss of compression, etc. is associated with lean mix, not too rich, which is what you would have with no fire.<br /><br />Go ahead and try a new powerpak. :)
 
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M Frey

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Re: 79' 70hp merc dies when i put it in gear

hwft,<br /><br />One more thing before you buy a new powerpack. I'm not familiar with your engine, but is it possible to swap the leads coming from the trigger coils and the leads going to the ignition coils, at the powerpack, on a cylinder that is firing correctly and the cylider that is having trouble? If your problem moves to the cylinder that was good then the problem is in the powerpack. If not, then the problem would be in whatever triggers the powerpack to fire the failing cylinder.<br /><br />I hope this makes sense.
 
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hwft

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Re: 79' 70hp merc dies when i put it in gear

hey guys, just wanted to give you an update on my nightmare.<br /> after replacing the power pack, coils,trigger coil and wires to the sum of $800 i ended up back in the motor and found that i missed the bad reeds on the 2nd and 3rd cylinders! both cylinders had reeds with big gaps and on the #3 there was one that had the whole end blown off of it. i got the new reeds in and it is running like a top now. :D thanks for your help, mike
 
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