'75 merc 500 running backwards

[tamarackstyle]

Hello again. Ive finally gotten back to the motor. To bring everyone up to speed, Ive replaced everything. And she would not run past mid range. come to find out that the red and blue coils were reversed. switched them and she ran beautiful thru all ranges, but just then the water pump quit. tore it down and replaced the impeller and pump components, but puzzeled because I saw nothing wrong with the old one. I put her back in the test tank, water out the pee hole, running fine then... the motor jumped and started rotating backwards, no more water out of the hole, and running horrible. shut her down and started her up again, and again backwards. checked timing, even pulled flywheel, everything checked out o.k. Fianally I substituted the distributor with an older points style one (500ml), and she runs perfect. Does anyone have any suggestions as to what component in the electronic ignition may be failing me and causing it to run backwards? And what harm, if any would come from leaving the points distributor in. Thank you.

 

[steelespike]

Re: '75 merc 500 running backwards

This is a total guess on my part but maybe the timing got too far ahead somehow.<br /> I dont think the old style distributor is a<br />problem as long as everything is hooked up and timed right.

 

[Yepblaze]

Re: '75 merc 500 running backwards

Cross fireing? ( a spark plug not supposed to firing at that moment actually fires of)<br /><br />A carbon track on one of the distibutor cap or components, poor or erradic trigger signal, plug wires running alongside each other inducing enough energy to crossfire.

 

[tamarackstyle]

Re: '75 merc 500 running backwards

I figuured that the timing was way off but cannnot figure out why. no carbon tracking, everything is new, never even seen water. I realize just cause they are new doesnt mean they work. I checked everything pertaining to timing, and triple ckecked and everything is o.k. I dont have the tester to check module but ohms come out o.k. and it is the third suubstitute. however I cannot see it being any other component.???

 

[rickdb1boat]

Re: '75 merc 500 running backwards

Checked the flywheel magnets???.

 

[tamarackstyle]

Re: '75 merc 500 running backwards

I dont think I have any do I rick? rember its a '75 the only year with that style of ignition. As far as I knew everything under the fly pertained to charging( hooked to rectifier and bat)

 

[rickdb1boat]

Re: '75 merc 500 running backwards

tamarackstyle <br /><br />That may be true on that year. Not big on the Mercs, but I figure I would cover the bases in case. Guess not as it has a distributor.

 

[jhreed]

Re: '75 merc 500 running backwards

Hi, On my Mercury 800 (80hp) 1972, I also had an electronic (hall effect) pick up. What puzzles me about your "reverse" running, which mine did many times(and well to) is that my electronic distributor fired on the up pulse and the point model fired on the down pulse (I may have this reversed) so I can see that you may have two different timing schemes going here for the two different distributors. Which MIGHT explain why yours runs well on the point model and not on the electronic model... hope this makes sense to you... (I read it and I'm now confused... )