Horribly running 570A w/Duoprop

[sbbamafan]

I have not been on here in a long time. I have an issue that has been getting worse over the last couple of seasons. I really want my boat to run right again and have grown incredibly frustrated. I'll tell you what I have done over the last couple of years trying to make it better. This has all been the result of intermittent skipping and some backfiring,etc. I replaced the fuel pump and filter and got nowhere. I then replaced the coil as the problem seemed worse after the boat warmed up. It seemed a little better. Fast forward to this year. I took the boat out and it was as bad as ever. Last weekend I changed the cap, rotor, plugs and wires. The boat started right up and I was optimistic. I backed out of my dock and idled to where I could gently apply throttle. It instantly bogged down and started backfiring worse than ever. Back to the dock I went...

It runs in idle and I have taken it to 3,000 rpms and it sounds ok - as long as there is no load. I then ran it and blipped the throttle some from the back with the hatch up. From there it feels as if there is a skip. After a minute or so, it backfired doing that too. I have a video of it if it will help diagnose - if I can figure out how to post it.

I am down to what seems only a couple of other possible issues as I see it now: distributor, ignition sensor, ignition module, or carburetor (Holley 4150). What are you smart people thinking the problem is? I am really desperate to get this fixed? Thanks in advance for your help!!

 

[Scott Danforth]

your going along and the boat starts intermittent hickuping and backfiring thru the carb? does it get progressively worse?

the ignition sensor / module is more expensive than a new Mallory or delco voyager distributor.

I replaced my distributor as I could put new cap and rotor on it, get about 3 hours out of it until it started hickuping again. each time I pulled the cap, the contacts were fouled. I kept 2 caps and rotors on the boat, would go out, swap them, come back, and then swap again. then spend the evening cleaning.

I think in my case the dizzy bushings were worn enough I was getting oil vapor in the cap, the advance springs were stretched and the ignition module was a bit flakey

either way, a new mallory dizzy and my problem went away.