My 35 ph. mercy wont run over 5mph at full throttle. What could be wrong?

SOURCE: 40hp 1987 yamaha outboard motor will run for 30-60

Sound like the fuel pump is not keeping up with the engine's demand. Check it out. Good luck. Hope this helps.

SOURCE: engine won't run unless primer bulb is being pumped

I have the same problem and may have a solution. I looked at the primer pump and it was cracked letting air into the system. When I pumped it my finger was over the crack and it worked fine. When I stopped the crack was able to **** air again. Take a look.

SOURCE: 1996 Mercury 150 Nitro EFI

Dont have the manual in front of me...recollect that there's two types of warnings. The pulsating warning is oil (starts with 30 minutes of oil left) or the fuel filter (or sperator, something like that) may have water in it. Running outboard with cover off, is a little black box that would have a red light lit if that's the case. If oil full & no red light, may be oil injection system...would also check to make sure lines aren't pinched, etc. Mine has been specific to oil the two times its gone off.

The full non-pulsating is engine overheat. Not sure beyond that.

Not much, but hopefully gets you going.

SOURCE: Mariner 25 hp 2 stroke hard to start then quits and won't restart

It sounds like the float is sticking in the carb. Since the carb is higher than the fuel tank it pulls the fuel in by vaccum of the engine. when running at high rpms, it can burn the fuel thats flowing into the carb, when you idle down, the bowl of the carb is filling up with fuel faster than the engine can burn it and causing it to flood. Then when it shuts off at idle it does not want to start back up because it is flooded. To make a long stary short, pull the carb and give it a good cleaning and your problems should be solved.

SOURCE: My mercury 35 hp outboard motor idle's fine but won't run

While at the river try to adjust the fuel air mixture. When you are on the water it puts the engine under a load and if that dont work then dont be afraid to bump up the idle stop screw slightly.