Mercruiser 3.0L Alpha 1 Gen 2 does this strange hiccup every minute or 2 mins...

Hi,

No matter what speed/RPM I'm at, it feels like the prop hits something almost it is such a bad hiccup.
It lasts for just a second then runs normal. It does this every 2 minutes or so.
On 2 occasions, it stalled completely when I brought the throttle back all the way.
I'll be driving along then chug chug bang chug then zoooom she runs normal again. Sometimes it sounds like a slight bang noise. It's NOT a rock lol, trust me on that. But it sometimes sounds like a metal on metal clang.
It will hiccup while driving forward every 2 mins or so, but sometimes I can go almost 10 mins without it happening at all. BUT, if I turn sharply, it does it every time. Sometimes just a slight chug, sometimes a very heavy chug or 2-3 chugs then back to normal again.

I purchased the boat 3 months ago, and have only had it out 4 times.

I've changed the plugs (the old ones had some rust on the bottom of them??), changed the fuel filter, inlet filter, oil filter and fresh oil, as well as greased everything.
It also has 2 brand new batteries, and an new isolator.
The boat is a 2000 Starcraft GT and the engine is original.

I'm thinking it could be water in the fuel, but I've been through a few tanks now, and use premium fuel (no ethanol) as well as Stabil on the first tank. I also put some Seafoam fuel clean in the 2nd last tank.

This is all the info I can think of right now, I hope someone can clue me into what might be going on here.
Thanks guys.

 

That sounds like an ignition problem. It could be an ignition module, faulty coil. Another cause is a bad shift interrupt switch or if it is out of adjustment.