'85 Merc XR2 150 hesitates on lowend

[wallymoose]

I have a Merc XR2 150 on a Ranger bass boat, after it warms up it runs flat on lowend, it allways plains out fine and runs about 60-70 MPH, but it's like there is no response in the throttle till you punch it down, we started with the carbs, cleaned and serviced they are fine. we did a cylinder leakdown test, fine. compression check: 110 psi in each cylinder, fine. checked stator, all fine. ready to give up we pulled the spark advance module, it is the low speed/high speed module, to find that the red wire has been melted down, it is still intact but the coating has been burnt, telling me that the wire got very hot. Could this be the source of my NO POWER on lowend problem? like i said the motor runs fine on top end, but is very flat on low end, allways idles fine never dies out, just a bad hesitation throttling up. when its cold the boat launches out of the hole fine untill it warms up, then FLAT. Could the spark advance module be the problem?? Any help will be much appreiciated! Thanks in advance, Moose

 

[2springers26]

Re: '85 Merc XR2 150 hesitates on lowend

all the idle advance mod.. is is to advance the timming when the idle drops below 500-600 rpms( IDLE)... BUT the module can take out switch boxes if not working properly because it's tied to the bias system... I'd be looking at the cold start valve on the starboard head ( has ruber hose run to the carb... richens the carb when cold..

 

[wallymoose]

Re: '85 Merc XR2 150 hesitates on lowend

but this isnt an idle stabilizer, it is a high speed/low speed spark advance module. what would the cold start valve do to make it hesitate??

 

[KCLOST]

Re: '85 Merc XR2 150 hesitates on lowend

Did you check the spark to all the plugs when the engine is warmed up?<br /><br />Let us know...<br /><br />This sounds like a fuel problem...

 

[2springers26]

Re: '85 Merc XR2 150 hesitates on lowend

stuck cold start valve would make the motor rich

 

[wallymoose]

Re: '85 Merc XR2 150 hesitates on lowend

how can i tell if the cold start valve is stuck??<br />also what would cause the wires to melt down on the advance module??

 

[wallymoose]

Re: '85 Merc XR2 150 hesitates on lowend

also, i will check the spark when warm....thanks all

 

[wallymoose]

Re: '85 Merc XR2 150 hesitates on lowend

this motor does not have a cold start valve, I have to think that the burnt advance module is the sorce of my probs....I will let you know when the new one comes in. thanks all

 

[wallymoose]

Re: '85 Merc XR2 150 hesitates on lowend

The advance module did not fix the hesitation when warm problem, any ideas??

 

[wallymoose]

Re: '85 Merc XR2 150 hesitates on lowend

WELL????????