libellav15
Petty Officer 2nd Class
- Joined
- Jul 3, 2010
- Messages
- 177
Hi guys
have you any idea about the following symptoms please - I am starting to pull my hair out and i'm stumped
Ok info - mercruiser 120 GM in line 4 - 1972 - standard ignition (plugs/points/condensor)
I bought the boat about 6 weeks ago, and the engine was good, but occasional hiccup and stall - so i decided on a service.
New plugs, points, condensor, rotor, dizzy cap.
New fuel filter, bypassed the water seperator for now, drained and cleaned the tank, new fuel.
Took the carb off and cleaned.
Cleaned flame arrestor.
Put it all together, started really nicely, but i can not get it to run smoothly.
the carb is a rochester 2bbl and as a result only has adjustment screws for idle - which i have adjusted to as smooth as i can with them - but the engine will not pick up revs without being hesitant and lumpy lumpy then when the revs build she runs fine, then back down to idle and again its lumpy.
timing is on, mechanical advance is cleaned lubed and working as it should.
the carb screws only affect idle so can't see it being that.
INTERESTING POINT....
I put the timing light inductive pick up on leads 2, 3 and 4 to make sure there is a regular spark (as it sounds like its missing while picking the revs up) and sure enough only intermittent spark on the timing light until revs pick up.
BUT - if i disconnect any of the leads and put a plug in and put to a ground the timing light flashes away nicely even at idle..??! possible engine earth issue?
so i am thinking low voltage somewhere until alternator boosts it, or leads are breaking down internally until current high enough to bridge gaps (no external arcing from the leads whatsoever).
Any advice on what to check, test or adjust would be VERY gratefully received please.
Cheers as usual guys
Adam
have you any idea about the following symptoms please - I am starting to pull my hair out and i'm stumped
Ok info - mercruiser 120 GM in line 4 - 1972 - standard ignition (plugs/points/condensor)
I bought the boat about 6 weeks ago, and the engine was good, but occasional hiccup and stall - so i decided on a service.
New plugs, points, condensor, rotor, dizzy cap.
New fuel filter, bypassed the water seperator for now, drained and cleaned the tank, new fuel.
Took the carb off and cleaned.
Cleaned flame arrestor.
Put it all together, started really nicely, but i can not get it to run smoothly.
the carb is a rochester 2bbl and as a result only has adjustment screws for idle - which i have adjusted to as smooth as i can with them - but the engine will not pick up revs without being hesitant and lumpy lumpy then when the revs build she runs fine, then back down to idle and again its lumpy.
timing is on, mechanical advance is cleaned lubed and working as it should.
the carb screws only affect idle so can't see it being that.
INTERESTING POINT....
I put the timing light inductive pick up on leads 2, 3 and 4 to make sure there is a regular spark (as it sounds like its missing while picking the revs up) and sure enough only intermittent spark on the timing light until revs pick up.
BUT - if i disconnect any of the leads and put a plug in and put to a ground the timing light flashes away nicely even at idle..??! possible engine earth issue?
so i am thinking low voltage somewhere until alternator boosts it, or leads are breaking down internally until current high enough to bridge gaps (no external arcing from the leads whatsoever).
Any advice on what to check, test or adjust would be VERY gratefully received please.
Cheers as usual guys
Adam