merc black max wont go above 1500 rpm under load

**stivov1** · 06-29-2017, 08:28 PM

had an issue while back with a motor that would run, idle great then when throttled down, it would just bog slowly at about 1500rpm, ended up being idle control wire was shorting itself out, once I fixed it, she roared, well having same problem with a 135hp, I inspected all wires, fixed a few, even swapped out stator, and still same thing, is possible for idle control module to be bad? i did try unplugging it and same result. where can I go next? trigger? spark, compression etc?

**FUJIMO** · 06-30-2017, 07:09 AM

If idle control module is suspect, completely disconnect it? We actually used to throw them away.

**stivov1** · 06-30-2017, 04:42 PM

I did and it didnt work, gotta be something else. how can I test switch boxes? is there a test for trigger?

**CNC_Guy** · 06-30-2017, 05:30 PM

Get yourself a Factory Merc service manual. It will teel you much more than the aftermarket ones will. Usually some on ebay.

**mn808gade** · 07-04-2017, 12:28 PM

sounds like its running on either one switch box or at least one carb is plugged or fuel delivery problem.fuel pump diaphragm broken? first do spark test,all should jump 7/16".take air box cover off,run motor,blip open throttles quickly, with finger and look at nozzle in each carb barrel,one at a time. should see a flow of fuel out top of each nozzle.get a spark plug wire pliers and pull each wire off plugs one at a time,its called a balance test.-th

**Waddlezz** · 07-04-2017, 11:49 PM

i had a similar problem with a black max 200. it ended up being my stator. once i replaced that, she would get up and go....untill i blew her up. However, the stator is what solved my problem.

**stivov1** · 07-05-2017, 07:41 AM

thanks for input guys, it ended up being the trigger, brown to purple had bad reading so replaced it and back up and running now!

**mn808gade** · 07-06-2017, 11:57 PM

SO IT WAS ONLY Running on 4 cylinders?-th

**CHICKENHAWK** · 07-07-2017, 09:21 AM

Originally Posted by CNC_Guy

Get yourself a Factory Merc service manual. It will teel you much more than the aftermarket ones will. Usually some on ebay.

Amen.

**stivov1** · 07-12-2017, 07:23 AM

ended up taking it back out and started acting up again, I had a parts motor and replaced coils and switch boxes, then it was flying! when got back to dock it died, sounded like it was running out of gas, so IDK, maybe fuel diaphram now? this thing has been a pain in ass!