My 80hp mercury outboard doesn't have any power under load, what could be my problem?

Question

I've done a compression check and all cylinders are between 116-120 psi. The motor starts and revs up well out of the water, but no power at all when under a load. It just gradually picks up speed as it goes.

Answer 1

Most often this is a carb. problem.  It can also be a problem with ign. system. Check spark using spark checker, don't pull plug wire and ground it.  Check the lower unit oil, for water.  Ok, now check your fuel, and drain carbs.  Water in the bowl, will prevent fuel flow.  check filters.  If all else checks out, rebuild carbs.   Good luck.

Answer 2

but it eventually reaches full RPM's?

been like this since you got it?  if so, sounds like your boat is underpowered, or else overpropped.  If your prop has any plugged vent holes, try removing the plugs.

Answer 3

sounds like you have the wrong prop on