some month back I posted a thread on my 1974 850 merc. it would fire and idle fine but die when you tried to advance the RPM above where the carb throttles started to open. You guys all gave great advise ( compression was 140 across the board and a new CDI trigger & CDI switch box had been put on this engine that came off of a 1975 850 merc. that had put a piston through the top of the block), So, rebuild the carbs, rebuild the fuel pump, new fuel lines, link & synk, filters, clean tank, second rebuild on carbs, re-link & sync, still same problem.
Called CDI and they questioned the type of battery used, I told them it was a NAPA 12V Marine battery, the tec. asked if it was a "dry cell" " AGM" or "maintenance free" type, I said it is a off the shelf "maintenance free" battery. The tec. then told me that a "maintence free" battery cannot be used with the CDI unit as the merc. engines that use a stator and rectifior need a standard type battery to control the voltage from going above 16v. He stated that the factory switch box draws 10amps and the higher voltage does not affect it, the CDI unit draws only 2 amps and any voltage above 16v will damage it. So, after many drinks and thoughts of dumping the motor into the briney blue, I removed the CDI unit and installed the factory switch box and coil back on the engine.... End of problem.
I did send the CDI switch box back to the factory and although they said that they could not cover it under warranty they, after reading my story of pain, did send me a new unit. Now to buy a battery that is not "maintenance free" and try again....
See you all later, it's cocktail hour.....I do wish to thank CDI electronics for thier time to advise me of the problem I was experiencing and sending me a new unit. >>>>>Stormmn
Called CDI and they questioned the type of battery used, I told them it was a NAPA 12V Marine battery, the tec. asked if it was a "dry cell" " AGM" or "maintenance free" type, I said it is a off the shelf "maintenance free" battery. The tec. then told me that a "maintence free" battery cannot be used with the CDI unit as the merc. engines that use a stator and rectifior need a standard type battery to control the voltage from going above 16v. He stated that the factory switch box draws 10amps and the higher voltage does not affect it, the CDI unit draws only 2 amps and any voltage above 16v will damage it. So, after many drinks and thoughts of dumping the motor into the briney blue, I removed the CDI unit and installed the factory switch box and coil back on the engine.... End of problem.
I did send the CDI switch box back to the factory and although they said that they could not cover it under warranty they, after reading my story of pain, did send me a new unit. Now to buy a battery that is not "maintenance free" and try again....
See you all later, it's cocktail hour.....I do wish to thank CDI electronics for thier time to advise me of the problem I was experiencing and sending me a new unit. >>>>>Stormmn
