outboard repair

Help! I need help with a 1998 Mercury 4 stroke 50 horsepower 4 cylinder outboard. Starts and idles good, as I ‘throttle up’, the engine stalls, seems to not run well enough to overcome the load from the prop. However, if you move the linkage by hand (not in gear) you can get the RPMs up. Fresh fuel, good fuel pressure out of the pump. There are four carburators. New coils, new voltage regulator, new plugs.
Treated fuel heavy with sea foam and let idle, still no change. Am reluctant to adjust the carbs, have not the knowledge to re-sync. Thinking CDI or Pulse Coil but this is getting expensive. Any Help Appreciated

Is the fuel line collapsed internally? Plugged or dirty filter between the pump and fuel manifold to the carbs?

Tom Sawvell wrote:

Is the fuel line collapsed internally? Plugged or dirty filter between the pump and fuel manifold to the carbs?

x2

Hello Iowa,
The fuel line to the pump is not clogged or collapsed in any way. Looks great even while running, with good stream of fuel flowing out when removed from pump with engine running. The 2 lines from the pump to the carburetors (1 line for each 2 carbs) are under pressure and do not think they would be able to collapse. These lines are not accessible at the carburetor end without removing the entire intake manifold with all 4 carbs attached.
Thank you

Does it have a clear fuel filter? Can you see anything in it? Was it running good then all of a sudden this happened? Was it sitting for a long time and then this happened? More information would help.

Check the plastic around the fuel pump assembly. Ours just broke and we had some of the issues plus is would die randomly. The pump ended up having a hair line crack in it. And it made a world of difference putting the new one in.

One of the nipples was the culprit.

fuel filter looks not plugged, as far as I can tell. (it is opaque and not highly see thru) Filter is before the pump and fuel out of the pump has good pressure. It ran great 2 months ago and was using fresh gas at that time. Boat sat for 1 month, went out and this problem showed up right from the get go when pulling away from the launch. Inspected the pump and appears not to have any cracks or irregularities.
Thank you for your time and thoughts