Electrical or Fuel issue?
 

Looking to see if I can get some help.. I have a 2000 ski centurion (mercruiser motor, carb), I recently had a season service completed (fuel separator, filter, ATF, oil, impeller and compression test). Let me back up, prior to having it serviced, the boat ran great... Once I got it back from the shop the boat did not run under load. It fired up and ran in idle and neutral completely fine. After taking it back to the shop the boat runs but cuts out and picks it self back up occasionally. Apparently they told me I'm over pressurized on my carb (11-12 psi). Here's my questions:

This sounds like it could be an electrical or fuel problem. Has anyone ran into a similar situation with bogging out and picking back up under a load? I don't think it's a fuel pump, but maybe an anti siphon valve or something. Could it be ignition problem... a bad coil?
Thanks

Sounds lie the ign/distibutor

You can't blame the electrical system for a carb fuel over-pressure. The lift pump just ensures enough fuel is available to enter the carburetor and 12 psi is pretty standard. The float or metering device should keep the bowl full of fuel so it can be suctioned into the venturi and throttle body. Ask them if the over-pressurization is from the float not closing properly in the bowl. If so, your engine may be over-fuelling and it would act similarly to the choke being on. That would cause rough running and a lack of power.

You can't be sure that it's something the shop did, even if the timing might indicate that. However, things to look for are: plug wires or plugs as they were out for the compression test; filter at the carb entry or junk on the float needle as the fuel lines were opened and something might have entered the line to the carb; rotor and cap just because they fail at the most annoying times; a vacuum or pressure regulating line being disconnected inadvertently.
I do not believe you over pressured your carb. Seeing how they are vented that seems actually silly.

Had similar issues with an 97 5.7L merc. I found a couple of the spark plugs had hairline cracks in the ceramic. Also took the distributor cap off and noted some corrosion between rotor and contacts. Replaced the plugs, cap and rotor, ran great. I would check those out, takes less than half hour to inspect everything and relatively cheap to replace if you find anything wrong

Check to see that cap is secured properly, it happens or all plug boots are down all the way.

Thanks. Since I've had the boat back, I re-checked all the plug wires (hoping it was something minor like this). I replaced the cap and rotor a little over a year now. I'll re-check it, maybe its something I just missed. The shop is telling me I should have 5-6 psi (not 12). Ill update with what I figure out.

pull some plug and see if they look flooded or fowled, they have picture on the internet was different plug symtoms are.... (flooding, lean, timing etc...)

Flooding At Idle RPM
If your engine floods at idle rpm, check the following:
1. Problem in ignition system causing engine to run rough.
2. Idle mixture screw adjusted incorrectly.
3. Bad needle and seat.
4. Incorrect float level or drop.
From Mercruiser

Inline pump is capable of 7psi max, I wonder what is making 16? did someone change the pump? (no pressure regulator on stock pump.)

Yes, 6-8 psi for carburetors with appropriate volume. I was thinking single stage pumps in a higher HP configuration.

you mean fuel filter in OP? sounds like a fuel delivery issue to me