HELP\200Merc\runs rough

[ricsan11]

i just bought a boat with a 88Merc.200hpBlack Max that runs rough between 1000&2000rpm[my favorite trolling speed].the compression checks fine& it has just been tuned. it starts easily & has no problem at any other rpm. being this is my 1st Merc i'm not sure this is normal or not. anyone who owns one of these have the same condition? thanks, richard

 

[MERCMAN]

Re: HELP\200Merc\runs rough

This is normal because at that rpm your butterflies are in between the idle and off idle progression holes in the carb what you are getting is a lean condition it want hurt anything.It's just these big engines don't like to troll for a long time. You might try different trim angles of motor position probably run better trim all the way down at this rpm

 

[ODDD1]

Re: HELP\200Merc\runs rough

Yes rick, these motors are sloppy between 1100rpm and about 2200 rpm.....if you need to run it there I can offer some suggestions....the bleed systems move alot of air around at these rpms and mercury has brought out a brass 'restrictor' that you can install inside the rubber bleed hoses....they will help.[while you got hoses off make sure check valves work too..they are on reed plate an you can suck air out but not blow back] merc usually setup these carbs rich..usually you can increase the idle air bleed jet at least .002" to lean out the idle....you'll never make these motors run smooth off idle but you can make it less irritating . good luck!