Mercruiser 4.3 issues with RPM 

I had the same issue, all it needed was timing correctly.

Mine was doing the same thing. Just ordered a carb rebuild kit, which is nearly impossible to find since i have the 4bbl carb and now im seeing that it may be the Thunderbolt box which will really suck since they arent made anymore

I want to start a 4.3 LX/V6 Alpha One engine, can you tell me the firing order of the wires that go to the distributor.

That looks just like my searay 200, judging from the interior. Hope you got it fixed.

hello you could put the electrical part of the ignition

so in these engine a lot of different things could contribute to this issue I will start with lifters because it happen when he goes up to 1200 RPM

i have this experience, for my case water go through cylinder 4 and problem come from gasket seal you can check by use a micro camera to check all inside cylinder after run engine 15 minute or run until engine have a problem signal

Wonder if this guy figured this out. Having the same issue

I have the same problem you know it can be a friend

Timing issue