Both engines loading up
 

I have had this load up problem all summer with the exhaust in the open position while idling and idling in gear in (No Wake zones)..I would have to rev it up and clear it out several times and even with doing that it would still run rough until i was over 1000 rpms. When i use the silent choice mode and devert the exhaust under the water it stops loading up and runs smooth ..I can idle in no wake zones all day long with no issues..BUT as soon as i open the exhaust it starts to load up .. I must have adjusted the carbs 100 times.. Really getting sick of it.. I checked for reversion, timing, vac leaks.. none found...

Stumped !!:eek:

what engines ?

x2, what engines and which exhaust ??

509 cu. 490hp. holley 960 cfm Nickerson carbs. 236 duration 114 lobe sep on cam, airgap dp intakes amd Msd ignition..
Problem was still there before the msd install..Timing with the msd distributor was locked at 34 degrees(idle).. I changed it back to springs and weights.. 18 degree advance with an initial base at 16 degree.. Total timing 34 degrees.. Either way made no difference..Carb adjustments.. 4 corner idle
1st-- 1 turn out on each..engine cuts out after 3 minutes..sounds like it ran out of fuel..2nd --- 1.5 turns out on each idles fine..Put it in gear and dies...add another 1/2 turn out on one idle screw.no stall in gear BUT starts to load up and drop cylinders... Close exhaust..to silent mode.. IDLES FINE NO LOAD UP....

I had a twin 650 Speed Demons that did the very same thing and when I talked to a performance boat engine dude in TN. He asked if I set the floats on the trailer or in the water. I did on the trailer, which I guess when in the water the boat level is much different. I reset in the water and all was good. Had about 20 deg. intitial with my MSD dist. and MSD boxes. Full in at about 1800rpms Total 36 deg at WOT..

I found my loading up issue...1 cylinder on one motor and 2 cylinders on the other motor were loading up with a spray of water from the exhaust ports but only at idle..It ran strong with no issues above 1000 rpms...
Heads went bad...

You mean it needed a valve job?

that'll do it ,good thing you did'nt bend any rods

No valve job... The heads are rotted or are leaking somewhere from the exhaust ports, maybe because someone before I owned it put bigger exhaust valves in them..I read i this site that if you grind too deep, you are getting too close to the water passage.. I could be wrong though..
Anyway.. I found 2 sets of 781's...I 'll leave these stock except for the new stainless valves..