1990 260HP Mercruiser Twin RH installation

"i have a 260hp merc installed

"i have a 260hp merc installed in starboard (RH rotation) in a twin installation. engine(s) were recently rebuilt < 10 hrs running time ago. star motor initially ran OK - now is running on 4 cylinders. others have been in engine compartment connecting throttle and gear controls for tower (all connections look good though). Non performing (NP) cylinders are #1,4,6,7 (every other one). i pulled plug wires at distubutor (HEI ignition) while engine running for these NP cyls and they make no difference in the sound or RPM of engine. ran comp test on NP cylcs - 150# consistent. pulled plugs and watched spark at plug ... all spark seems weak to me. swapped ignition amp from port motor ... same deal still running on four and port motor is fine - so niox the ig amp. i have NOT swapped ig coil and dist internals - YET. the carb on this mootor gave us problems in the beginning with spitting back through. Any ideas? cross fire? if ignition prob how is it running on 4? fuel? HELP! I always get the ones that aren't on the troubleshooting diagram."

"did you check the timing? I w

"did you check the timing? I was thinking the timing chain could have jumped a tooth or something. not sure what compression would read though if that happenned, but distributor could be off.
If there is the same weak spark on all 8, but 4 aren't contributing, then I suspect timing. And then of course, the weak spark is another issue."

"It could be a couple of thing

"It could be a couple of things.
I think if the timing is off, its not just by one tooth. If it was "spitting" back thru the carb, that's not a carb problem, thats a valve timing problem, i.e., one or more intake valves open when they shouldn't be, or ignition timing waaaay off and spark firing during intake stroke. First and easiest check...
1) remove #1 spark plug.
2) ground center hot lead of coil.
3) put finger over spark plug hole
4) jog starter until #1 is on compression stroke.
5) Stop piston at top of stroke ( may take a few trys. ( a piece of soft wire in the spark plug hole will help with this)
6) REmove distributor cap
7) Rotor should be pointing pretty much at the connection for #1 spark plug.
8) If it is, make sure other spark plug wires are connected per the correct firing order."

thanks for all the help guys .

thanks for all the help guys .... timing was the problem sort of. I looks like my mechanic (the same company - not the same mechanic that put the engines in) had a "brain aneurism" a couple of weeks ago while working on the carb spitting problem. I'm just guessing because I haven't spoken to him yet but I assume he saw the firing order (LH rotation) on the intake manifold and changed the wiring on the dist to match! All I did was swap the wires around to the correct firing order for RH rotation motor and shazaam! i think i'll be finding a new mechanic or just do it myself. thanks for the help.