BlackMax runs rough at 1-2K rpms-Why?

#1 07-23-2006, 03:33 PM

Just had the carbs rebuilt and fixed the plug fouling but not this. Just off idle into trolling speed it runs real rough. We like to troll around 11-1300 rpm's which is maybe the roughest spot. Runs real smooth at 2000 and up.
Any thoughts? >:(
Trollercoaster

Airslot · #2 07-23-2006, 04:26 PM

Here's a thought. Check all your connections in the switchbox area making sure everything is clean ans tight. THe stator has three sets of windings, low spped, high speed, and charging. You might be losing the low speed winding in the stator. If you have a manual you can check without pulling the flywheel. IF you hava meter I could get the wires and readings for you if needed. If the low speed windings go totally you'll be dead in the water. I lost the high speed windings two years ago and it wouldn't run above 2k or so.

Airslot

#3 07-23-2006, 07:16 PM

Thanks for the input! OK, here's the history. Last summer (Aug?) we're out in the Gulf o M and a couple of times it idled rough and died. Then, 4 miles out, 5 miles from the pass, it doesn't fire at all I know there's no spark so I call towboatUS. My favorite mechanic gets it, says it's the stator, puts a new one in and it runs fine. Then the next trip or two it runs rough. I know the plugs are old and oily so I change them--runs fine.

Then end of May this yr it dies, runs only 3-4 sec then dies, finally it runs, blows oil like it's on 50:50 for a while, then runs OK, then skips like you turned off one cylinder, dropped from say, 4800 to 42 instantly. I thought it was electrical. Did cranking spark test-all ok. Did comp check, I got all 95-100, mech got 120 on all. He "rebuilt" carbs said there was something bad on a float needle/seat, etc. Now it runs fine at high speed but is bad at 1000 to 2000.

What about, when I rebuilt this motor, had #1 and #6 sleeved and upon the advice of the guy who sleeved it, up'ed the jet .004 on each of those. When I pulled the plugs (which were almost new) on that other problem, I noticed #1 had just a little crud on it, the others looked fine. Soooo, would you think maybe I should come back down .002 on #1? Could it be oil fouled until it opens up some? Sorry, I don't have my book with me, I think std was .074 and I went to .078. Is there a low speed jet?
Trollercoaster

Airslot · #4 07-23-2006, 07:38 PM

I'm no help on the carbs as I've never had to mee with mine, yet. I like to go through mine every 6 months and check electrical connections to make sure everything is clean and tight.

Airslot

reelapeelin · #5 07-24-2006, 07:51 AM

troll, I had a buddy w/ a Merc...he had a mech ''mess w/ the jets'' and it too ran great in the upper RPM ranges, but rough in lower ranges...unless there's some substantial reason for re-jettin', I'd stay w/ stock sizes ;) ...

bigshrimpin · #6 07-25-2006, 01:45 PM

What year . . . and which carbs? There are low speed jets, but I don't think that's your problem if you've clean them recently.

Spark advance module, low speed idle module. Yank them both off and have a mechanic set the timing to around 5 degrees at idle and 23 or 24 degrees at WOT. Could also be reeds but I would start with timing.

Plugs should be paper bag brown. I wouldn't mess with the original jets.

Get rid of the oil injection and premix. Also check the condition of the bleeder hoses.