no matter what it should still start, i get them with dead battewerys all the time and put the switch to all and the boat will fire..you mentioned that your tach was going in circles??? somethine on the grey wire mat be grounded..pull off the grey wire on the neg side of the coil and see if it starts..

also undo the main plug that goes to the main engine electrical harness,,clead and pry open all the terminals,if one was loose and from it getting hot it melts the rubber then someetimes the terminals will touch or coat the terminal with rubber when it cools off..

It's an efi engine, so the tach lead doesn't come from the neg. side of the coil. The ecm sends the tach signal. A bad tach will cause them to misfire on the top end but I haven't seen it cause them to not fire at all. Guess anything is possible though.
Eddie

ok guys going to give these a try and thankyoiu for you input ill let yoiu all know what i come up with ,and thanks again

earlyer today we put 12 volts to the red wire that goes into the coil the top plug on the coil , still no spark was that a valid test to get 12 volts to the coil

whe the motor runs the tack works fine , the motor does have a little surge in it betwee 800 to 2000 rpms but it not to bad i put a volt meter on the batteries both at rest but still hooked up but the battery switch in the off position and they both read 11 volts

if you have a strong battery (+13V) just take a wire from the + side of the battery and connect directly to a purple somewhere on the engine.

If it runs you have a wiring harness problem somewhere...

what about the pick -up coil under the dist. cap

ok guys i bought a new battery 1050 cca, use my battery charger to supply 12 volts to the purple wire in the harness that goes into the ecm and still no spark wont start i also isolated the other battery while i tryed to start the motor, i did notice that the motor sounded different when it truned over when i gave the purple wire 12 volts which was really like 15 volts , sounded like the motor had a different sound when turning over like it was zinning or wining kinda but when i took off the lead to the purple wire it quit sounding like that , i did fire once at first then nothng after that , check grounds, fuses , tryed to hot wire it at the key switch still nothing any more ideas guys , thanks james, oh and not corrsion in the 10 pin plug , the wiring harness is new like 4 years ago., the tack works fine when the motor started before

i didnt replace the pickup coil in the dist , should i do that next ?

You haven't changed the ignition module in the distributor? I thought I read that you did change it? If not, yes, change it out.
Eddie