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Old 08-04-2012, 11:32 PM
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EST dizzy, SBC HELP!

I have been searching for a solution to a boat problem.

background info:
The engine is a 1989 SBC 305 1 piece rear main, center valve cover bolt block. Boats have no vacuum ports-nada, no pcv, no carb ports, nothing, and it is all mechanical advance. Carburated-no comp controls, early dumb style rochester. It had a mallory points system (yes, 1989 points) which was converted to electronic which corroded and didnt work anymore. The boat comes with a "shift assist module" where there is a switch which detects pressure on the shift linkage and it grounds out the + side of the coil intermittenly to cause the clutch (which is basically two castle nuts top to top which just spline together roughly) to "jiggle" with the stuttering engine and engage/disengage fully.

background info on clutch control:
Okay, on boats, there is no clutch, it is figgured that the water is soft enough so when you put it into drive, it is simply a system where a castle-nut looking "clutch dog" is pushed by a yolk into another castle-nut looking "clutch dog"-CLUNK, you are now in gear. the gears have a little back-cut so the more load, the tighter they suck to each other. When you want to get into neutral, you have to overcome this back-cut force that holds this drive engaged, hence the Electronic Shift Assist or ESA, as the boat coasts, there is a little backpressure on the prop-essentially the boat is coasting which releases the backcut, and this is given a little stumble. Mercruiser does it simply, and somehow they jumper one of the leads (I have been told its "B" of the GBRE but when I supply +12v to this leg the dizzy drops the spark altogether) OMC, the outdrive I have does it clumsily, needing a jiggle mod which stutters a ground lead on the + side of the coil (moving away from mallory, I chucked this system in favor of the Mercruiser style) but now I dont know how to make it work.

What I did:
took Mallory off, bought an est (pn 1103952)-8 pin module and coil off ebay, removed the resistor wire, hard wired the dist to the ignition (black to the ignition, grey to the tach and ran a pigtail direct to the + C side of the dizzy and left the 4-pin GBRE port untouched). Removed the shift assist because the shift assist just wont work. Set timing, and it runs great. No computer though, so its running in "fault" mode, so it only does one advance step to about 12 degrees.

Problems that need solution:
1: there is a mode, or wires that get jumpered in the dist that retards the timing to 0 degrees-I think it is what the knock sensor triggers that is what the boat guys do to "jiggle" the clutch to get it to fully spline. What pins on the dist need to get jumpered and what pins get voltage (or ground) on the dizzy to cause this to retard to 0 at idle?
2: I need to get this thing to give me more advance. It runs strong at up to 2000 rpm but is just flat at higher revs cause it just does not advance. I figure that I might need to add a spark control module or something-I figgure it will plug into GBRE but I dont have fuel injection or ANY sensors on this motor, so if i was gonna add a spark control of some kind but it would have to be a pretty dumb unit cause again, the motor has no inputs, no sensors, and nothing electronic whatsoever.
3: can I add a knock sensor? being a boat, this motor is under 100% load almost all the time, and if i advance the timing and it gets detonation, I will not know until I blow a hole in a piston.

I have posted in boat forums, but those guys, although helpful to some degree are pretty dumb when it comes to making frankenstein come to life.

Thank you in advance.

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