1974 ski nautique 351 w pcm

I have had this boat for several years and have not been able to get set properly.new Mallory electronic distributer from ski dim put in.had Mallory 4160 carb rebuilt twice.new plugs,wires .have timing set to 5 degrees and still sluggish on hole shot or get a pop noise like to much fuel in carb .i turn in the air fuel screws to cut down on fuel and it only gets worst.I Tried using vacuum gauge in between pvc valve in valve cover and carb to set screws but no luck. Need advice

Sorry new to website and have 2 post on the go for same subject.didnt think first one went thru.have timing set to what mechanic told me and ski dim but reply on other post agrees its timing

Map your timing curve. Start at idle and watch what it does and record the timing from idle to 4,000 RPM. Once you know what it does and when it does it you can fix it or rule it out as a possible cause. Timing is set on a mechanical advance and can be adjusted but you need to know what it does before changing it.
Map idle, 1,000 RPM, 1,500 RPM, 2000 RPM, 2,500, every 500 RPM all the way to 4,000.
It will stop advancing at some point between 3,000 and 4,000 n0rmally.
You can do this with a set back timing light or buy a harmonic balancer tape at a speed shop or from Summit and it will allow you to read the timing all the way up beyond 40 degrees advance.
Maybe your distributor has very stiff springs and it is not advancing as fast as you need or is coming in too fast. It should advance exactly the same each and every time you rev the engine and it should advance very smoothly with no stops and stutters.
Takes time but the test is free.

Thanks for the advise.should have joined this forum years ago.going to start with timing at 10 degrees and map it as you suggested.

Something is amiss, take a close up photo of the carb on each side as it is now, maybe we can identify something.

Hopefully you can see pictures of the carb.

Then again, this might very well be one of those really funky marine carbs that KenO talked about someplace else.
Get us a list number off the horn of it. That should tell us for sure.

I stood up and the blood drained back from my head. Now it maybe looks like only the secondary bowl is adjustable and the primary has a plug in it.

It all just looks weird to me.

It's really clean though...LOL

Sorry guys bear with me.Not much of a computer guy as you can tell by the way my pictures were posted.get that number off air horn and post

I think you may have looked in the wrong spot, the attached picture shows where to look.

The number you found was probably on the side.

Exact same list as my 74
Carb looks way too clean.   Did you paint the carb ???
And it looks to have been Frankenburetored at some point in it's life.

It just came from cr carb rebuilders.They have some process which he did not care to share which returns it to original colour.i think that actually sand blast it when it is all apart