bogs down at WOT

[woodshole]

1993 90 hp evinrude. runs fine at low speed. after 10-15 seconds boggs down. if i pull back on throttle its okay again. the boat ran perfect for about 2 outings and then started this. primer ball seems alright. i'm going with a fuel problem ( could be electric though). maybe a clogged orfice. bad fuel pump. its a vro pump and i'm premixing. stuck float? vacum? i don't know... maybe you know...

 

[fishnfiend]

Re: bogs down at WOT

You are going to have to narrow the possibilities to get help on this board.<br /><br />Have to start with fundamentals:<br /><br />compression - report #'s<br />spark - all cylinders jump 7/16"<br />timing - timing base is advancing properly<br />fuel delivery - clogged vent, air leak from any of the several connectors, crud in carbs. Pull the drain screw from the bottom of the carbs and see if you can pump fuel through the carb (squeezing primer ball - one carb at a time).<br />If you are going to fix it yourself, probably need a shop manual - well worth the $35.<br /><br />When you report back with your findings, someone on this board will knock your question out of the park for a home run!

 

[mark.aa]

Re: bogs down at WOT

have the same problem with my 89 60hp vro.ran fine at 3/4 throttle for 15 min then started to loose power ,had to go to full throttle to keep same speed,then lost all power and had to keep throttle wide open just to keep motor running at 2000rpm .was also running on premix 50:1.junked vro pump and put a new standard pump on it think it,s a johonson v6 pump,cleaned coils plug leads,changed plugs.water pump and new thermostate, as sombody had removed the core so it was always open and the pee hole water was always cold .had to mod the peehole outlet on lower side of exhaust to top of block as the motor could be starved of water on upper cylinders but would always shown an outlet stream.check yor fuel pump is pumping out fuel.am testing mine at the weekend and will let you know how it goes.

 

[mark.aa]

Re: bogs down at WOT

boat worked fine ,check all you fuel lines for loose joints that could draw in air not fuel,check fuel pump pulse line from block to fuel pump,air leak here will not let pump work.last thing ditch that vro pump!