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2011 merc optimax won't run at certain revs

S

stormpatrol

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HI Guys have a 2011 optimax 3cyl 2 stroke ok ,starts and will run fine at low or high revs after a short period lets say when hot won't run smooth below 3200 revs coughs and splutters is hard to get revs back up but will after a while rev out , back at ramp and on the muffs it plays up and stalls , got mech fuel pump rebuilt ,got new plugs and new fuel filter, she has 109 hours on it any ideas its driven me mad
 
You will need two fuel pressure gauges to start with diagnosing this engine. One for the fuel rail and one for the Air rail. Please post the serial number so I can see which engine you are working on.
 
HI again thanks for the heads up ill get that info asap , what i have found today is my battery cable had a really bad connection on one end , although i run duel batteries one battery is or wast in the loop , it is now , i wonder if this could be my problem ? optimal need good voltage i have read .
 
Understand that the belt that drives the alternator also drives the air compressor. If that belt slows too much or slips on the air compressor a list of performance issues will appear. If the belt tensioner is weak you will have problems, If the belt is getting wet you will have problems, if you over load the alternator you will have problems.

I would put the biggest CCA batteries you can find in the Group Number that you have. I install 1000 CCA batteries on all Opti's. If equipped, I would never run the boat with the battery switch on "both". One battery at a time.
 
ok motor was back into merc dealer today , was told all good very confident prob solved .... back in water got her up to running temp loss of power and spluttering , straight home on the muffs in the yard , same symptoms removed leads one at a time , bingo bottom lead made no difference stop motor swap leads over restart same problem missing farting etc remove bottom lead no change in motor still missing so it looks like coil pack breaking down when hot . would you agree ? plugs are brand new first run on them , we swapped them chasing this problem
 
Ok chris have been back in the water today, and swapped the bottom unit to the top problem followed the coil pack to top cyl . would you think mercury dealer will swap all 3 coils under warranty or just the one breaking down , the reason i say this is, motor out of warranty next month, thanks for your help chris :cool:
 
dealer thought i may get 3 ha ha no only one , tight buggers . if one has failed i would think that the others were on the way , or am i thinking too much ?
 
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