Mercruiser 3.0 RPM Drop Every Few Seconds?

[CLi87]

I have a 2007 Sea Ray 175 with the Merc 3.0 w/ Alpha one, just rebuilt the carb and fresh gas, it idles fine and runs great more or less, it'll get up and go and plane easily, but while I'm cruising every maybe 15 sec or so the RPM's will just suddenly drop briefly and then go right back up to normal. I was thinking maybe an air leak but I sprayed the area around the carb and intake manifold with carb cleaner to see if the engine would stumble but nothing. I tried searching the forums but couldn't find any thread with my exact issues or perhaps I'm using the wrong keywords. Any ideas what it could be or where to look?

 

[Scott06]

Do the dash gauges drop when it happens

Might look at ignition wires cap and rotor maybe a loose plug wire . What do spark plugs look like

 

[CLi87]

I forgot to mention new spark plugs, new wires, new distributor cap and rotor. The dash RPM gauge does drop and I feel the boat pull back just slightly, it's not a very abrupt drop, more like a smooth rpm pullback then it just goes right back up to where it was and cruises just fine.

 

[dubs283]

RPM's will just suddenly drop briefly and then go right back up to normal..... Any ideas what it could be or where to look?

Based on provided info I would inspect fuel delivery, mainly focused first on fuel tank vent line then supply to pump. If needed a vacuum test of fuel pump may be in order

 

[CLi87]

Based on provided info I would inspect fuel delivery, mainly focused first on fuel tank vent line then supply to pump. If needed a vacuum test of fuel pump may be in order

I was actually just thinking the vent line too, I filled up fully today and afterwards it took me awhile to get it started, normally it starts on the first crank.