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jguinter
06-25-2011, 04:56 PM
I decided to upgrade to electronic ignition and must have screwed something up. The boat was running Ok prior to my work, but would idle poorly and hesitate after it was hot.

Boat is a 93 Prostar 205, Indmar 351W (285 hp). I purchased an entire new Mallory Distributor assembly from SkiDim, got the matching coil as well. Upon receipt, I noticed the wiring diagram for the mallory called for a ballast resistor with the new EI distributor. So I picked a mollory resistor since I searched my entire electrical system and found none on the existing system.

I turned the engine to BTDC, marked the rotor, installed the new distributor, set timing at 10 BTDC, started the engine and it ran very rough and would not run at idle. I played with the timing and it finally smoothed out around 30 degrees at 1000 rpm. Even after warming up, it still is struggling to idle. Acceleration is very strong and no hesitation. It runs smooth at 1000, but below that it really struggles.

What could I have possibly done wrong in the distributor install? From everything I have read on the forums, timing is always around 10-15 degrees. 30 seems way outside the range.

Any ideas?

mtajpa
06-25-2011, 05:00 PM
Check the firing order. Maybe you crossed a couple of plug wires on the cap.

jguinter
06-25-2011, 09:25 PM
I was pretty meticulous when changing them over, and have double checked, all are right. It actually runs really well in the middle rpms 1200-3000(as high as I have rev'd it) very smooth and does not sound like misfiring at all.

Could it be that I am one gear tooth off?
I counted 15 teeth on the dist. gear, which means each tooth equals 24 degrees of rotation. I swear everything lined up right where I took it out, but maybe I goofed.

Also, it seemed that the aluminum base of the new dist was hot to the touch, is this normal?

jguinter
06-26-2011, 11:53 PM
OK-I win the jack@$$ mechanic of the week award. after tearing my hair out trying to figure out what I could have done wrong, I stopped and listened to the engine when I could get it running, and heard a loud air sucking sound coming from the carb. I discovered that the plug covering the vacuum port on the carb riser was missing. This allowed the carb to suck insane amounts of extra air preventing the engine from idling.

As best as I can tell, when I originally installed the distributor, my initial timing was off and the engine backfired once...I am guessing that the backfire blew the plug out of the hole and began my two-day search for an electrical problem with the new distributor.

With a new $0.20 rubber plug, the engine runs like a top. I set the timing to 10 degrees BTDC @1000 rpm and the engine has never run better.

Someone needs to come and take away my tools, revoke my mechanic's license, and get me back on the lake so I can think straight.