1988 Mercruiser 3.0 looses power at speed, was fine yesterday

[rehgarde]

1988 Mercruiser 3.0 looses power at speed, was fine yesterday.
We just trailered our boat to the Hudson to visit family.
Yesterday we went water skiing, today we had the kids tubing.
About 30-40minutes in today, the engine started to loose power at speed ~20-25mph and finally at full throttle would only go idle speed.

What could cause this sudden issue?

This year the engine had:
Carb rebuilt
Fuel filter/pump cleaned out
Tank was empty, so all new fuel
Fuel line from tank to pump changed because it was restricted
Points changed
New plugs

Some of this was done at a shop, we just got it back last week.
It will idle fine, rev at the dock fine, drive around at idle speed fine, but will not hold anything over 20mph.

Had some electrical issues also pop up around same time, horn stopped working, tach is off sometimes, nav lights stopped .

Where do I start?

Thanks!
Brandon

PS my plan(s) include,
Disconnect tach
Check fuel pump filter
Check carb filter
Fill with gas, at half a tank now?
Timing
Scuttle and take up new hobby

 

[Scott Danforth]

Start by checking your fuel

 

[rehgarde]

PROBLEM SOLVED!

I filled the tank up and took it for a spin, same issue, even more pronounced when going around turn. It would pulse heavily.

Disconnected fuel line at the pump, and blew back into the tank, and YES we have full power back!

We were able to do a full day of skiing and tubing,
Thanks for all the help!
Brandon

 

[jrs_diesel]

You should expect that problem to come back. That means you have solids in your fuel system that need to be dealt with. If I were you, I would order a spare fuel filter and keep that in the boat in case you had to replace it while out on the water.