1979 470 mercruiser keeps burning out condensers! Has anyone had this trouble?

skelly · Sep 18, 2001

I have a 1979 wellcraft boat with a 79 470 Mercruiser that keeps burning out condensers about every 30 or 40 HRS.Does anyone know what might cause this? Thanks! Skelly.

Rex · Sep 18, 2001

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

JUST GO WITH A BIGGER ONE AND MAKE SURE IT TIGHT.SOUNDS LIKE THE WIRE NEEDS WORK. GOOD LUCK REX

Rex · Sep 18, 2001

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

PUT A PIECE OF FIBER BOARD UNDER IT TO KEEP THE HEAT OFF OF IT,BUT MAKE SURE IT HAS A GOOD GROUND TO IT. REX

skelly · Sep 18, 2001

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

Thanks for the advice Rex! What do you think is causing this. Can I use a condenser from a auto parts store or do I have to use marine parts? And can I glue the fiber board to the condenser? Thanks for your help, Skelly

clanton · Sep 18, 2001

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

Needs a good ground, like Rex said. Check restance wire between ignition swith and coil +, should be voltage drop to about 9 volts engine running.

Rex · Sep 18, 2001

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

YES YOU CAN. I THINK THE HEAT MIGHT BE THE PROBLEM I HOPE. THANK YOU REX PS IF NOT WRITE BACK AND LET ME CHECK A LITTLE DEEPER. RED SKY AT NIGHT MIGHT BE ABLE TO HELP TOO.

jimdi · Sep 19, 2001

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

You also might want to check your voltage regulator - to high an output would give you a hell of a spark - but would cause problems with wear on plugs - points - condensors and other ignition components.

Rex · Oct 17, 2001

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

Are you saying it still does the same thing? Rex

petryshyn · Oct 17, 2001

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

How is the capacitor failing? Is it shorted internally? Is it a no start condition, are the points burnt blue, are they pitted? The condition of the points can help determine the type of failure. Condensers and coils are matched to each other. Coils and condensers from other applications shouldn't be intermixed unless their specs are the same. I think you have to answer Clanton's, Jim's and Rex's questions to get to the bottom of this. I think you have to be more specific in how the condenser is failing, otherwise its a shot in the dark repair.

Good Boating!!

12Footer · Oct 17, 2001

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

All of the above. My personall theory is heat and moisture. Both destroy caps,both in radios and outboards. This is one other good reason not to leave the fishfinder on it's mount,(besides the fact that somebody might steal it.). Like batteries, they have electrolitic material in them,seperated by an insulator. As they heat up and cool, the insulation warps, and they short out. On the pre-80's Mercruisers, there was a resistor inline with the condensor (cap)and the coil. If this is bad or missing (some folks jumped them), the rotor and cap would melt down. Symptoms of a bad resistor are a normal start, quickly followed by a stall.

skelly · Oct 18, 2001

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

Thanx for your Input guys! The points look in good condition to me. I can be cruising along and the motor just shuts down,and sometimes i can wait for 10 minutes and it will start up again, 2 other times it quit and that was it. 1 time It would not start at all at the boat ramp,But it ran fine the day befor. Its the condenser every time. I can't figure this one out! Thanx Skelly.

petryshyn · Oct 18, 2001

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

Be darn sure its the right coil!!!!If it is, check the old condensers to see if they actually are bad (should have no continuity between lead and body) I would turn engine over by hand until points closed....turn key to run position.....measure voltage(as clanton and 12footer recommend) from the coil + terminal to engine ground. Voltage should be 6-9volts (if 12 volts, ballast resistor is an issue). turn engine over slightly till points open....voltage should go up to battery voltage(12-13v) If voltage stays low with points open(6-9v) you have a short to ground in the primary circuit( distributor lead, point assembly, coil primary or yes...the condenser) if the condenser proves to be bad, you could consider mounting a new one externaly(but as close to points as possible)this would reduce heat as rex and 12footer suggests Good luck!!

teddy · Oct 24, 2001

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

Re: 1979 470 mercruiser keeps burning out condensers! Has anyone had this troubl

I have several suggestions, as I cannot do any testing. Make sure you have a good ground to the engine block directly from the battery. You could even run a light gauge wire straight to the distributor housing as a redundant ground.Make sure the capacitor is also well grounded. Learn how to do a dynamic voltage drop test, and check both - & + sides of the circuit.You should have less than 1/2 volt drop, and this is much more accurate than testing resistance. Finally, most of these types of problems are caused by a bad coil or incorrect coil voltage supply; a bad resistor, no resistor, a resistor along with a resistor coil( too much voltage drop) , or an overcharging situation, (over 14.5 volts while running at 2000 rpm). Hope this helps, it is pretty comprehensive and should pinpoint your problem. I like smoking guns! TIGHT LINES! Carl

1979 470 mercruiser keeps burning out condensers! Has anyone had this trouble?

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