'71 Merc 1350 Bogs after New Trigger

[gcleehusker]

My old distributor body was overheating and causing my engine to shut down with the cowling on - on the 1971 Merc 1350, it also had an intermittent spark. The new body (trigger) is now installed and it runs fine on the muffs but bogs on the water when the throttle opens, and I've adjusted the idle mix. It ran fine before, if a little off because I must rebuild my carbs this week, but I expected it to at least run. I've got the base timing set at 2% per the manual and the max advance set at 18%--tried 21%, but no difference and I want to be safe with the 18%. Since the last successful run, I've added a lead substitute (tec6000) for the first time and am using 93 octane premium fuel. One thing that may be wrong is the orientation of the distributor disk--with no markings I had to go by the wear patterns to determine which side to face the rotor and which side to be on the bottom towards the trigger--Pretty sure I have it right, but do have a new disk on the way. My top dead center does not line up exactly, so I've tried it with the distributor gear set the half-notch forward and backwards. The forward setting was stutter-and-ping-horrible, the back setting just bogs with ANY throttle. I'm going to replace the distributor disk on the chance that the hall sensor is confused with the old disk (it's a bit green but thought it would do the job). I am getting spark on all six cylinders (checked with timing light) and have 130psi plus of compression on all six. I've got a new CDI switch/coil combo that worked prior to the trigger replacement. I hope that with spark on all cylinders, the trigger is working. I've seen the trigger troubleshooting for this model and, since all six are firing, don't see the problem that relates to my situation for testing the trigger. Is it possible that the spark is so good now that my carb rebuild is just mandatory? Could I have the disk in upside down? Could I have assembled wrong. Any thoughts?

 

[SpecHunter]

Re: '71 Merc 1350 Bogs after New Trigger

Sluggish is as sluggish does.... Sounds like ya covered all the other bases.
I would do the re-build , set the carbs to minimum adjustments , and take it to the lake and tune it under load right from the get-go. no tuning with muffs.

 

[Chris1956]

Re: '71 Merc 1350 Bogs after New Trigger

The timing disk does need to be in correctly. I had thought they were stamped with an "up" on them. Idle pickup timing should be 4-6 degrees BTDC. Verify your timing pointer is set correctly, and recheck/reset the timing.

BTW - Bogging is most always idle mixture. The carbs need to be synched to the mixture needs of the two cylinders they supply, and then richened up enough to allow acceleration.

 

[emckelvy]

Re: '71 Merc 1350 Bogs after New Trigger

The "chopper" discs are stenciled but of course that fades with time and Green Stuff! It Most Definitely makes a difference when they are swapped.

If your max spark advance stop screw seems to be way far in or way far out, that's a good indication that the disc might be upside down.

If you find that the max timing adjustment is in a 'normal' range then maybe it's OK.

I'd still check though if there's any doubt at all.

Another possibility if carbs don't help would be to check the idle bleed restrictors to see if they've been sucked out. May or may not contribute to loading up/bogging off idle but if you rule everything else out and still have the problem, it's likely worth a look........ed

 

[gcleehusker]

Re: '71 Merc 1350 Bogs after New Trigger

Yea, it's good to hear you folks comment. I'm especially thinking about the max advance screw being almost all the way in and my 2% BTDC base timing being right on at the most clockwise position the distributor is able to turn. Even after lining up the rust shadows and such on the disk and getting it in the way it was (and it's pretty funny talking about putting back such an old greenie, anyway)...anyway, I'm going to install the new disk and do the carb rebuilds. A guess everyone agrees that the trigger is probably fine if it idles smoothly and I get spark on all six?

 

[emckelvy]

Re: '71 Merc 1350 Bogs after New Trigger

guess everyone agrees that the trigger is probably fine if it idles smoothly and I get spark on all six?

All that trigger does is tell the switchbox when to make a spark. Sounds like it's doing its job!

Something else does come to mind, you've been doing a lot of fiddling with the dist cap and wires, make sure the cap is Super Clean inside, the center carbon contact is free to move, no arcing or track marks inside the cap.

Fire 'er up at night and make sure you don't have a "ring of fire" effect on your spark plug wires. Leaky wires will surely sap your ign's strength and simulate a "lean" condition.

Cheers.......ed

 

[gcleehusker]

Re: '71 Merc 1350 Bogs after New Trigger

Funny you should say that, Ed...

I did also order a new set of wires and fresh boots (plugs are new and only showed some signs of normal operation, if maybe a bit rich?). The cap will also get a new center brush. The contacts are old and slightly darkened, but no stray marks, so the cap will stay with me for now. Sounds good, and thanks for the help. I also noticed that my 2% base timing number from the manual could probably go to the 4% that was mentioned. I do have one of the serial numbers starting with a 3###, but I'm thinking she might run better from 4%. I'll repost in a week or so and let you know the results. Thanks again.