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1997 mariner 75hp triple, bottom plug black and wet

F

forest66

New member
hi ok i bought this engine with a electrical fault , the rectifier was burnt out , the stator was off when i got it , i replaced the rectifier, the stator checked out in range when tested, after repairing the wriing , i ran it on tick over it was sounding ok, i only ran it briefly , i fitted it to the boat thinking it was all ok,
, in doing that i got the battery leads round the wrong way because the old mariner had a red sleeve on the neg wire !! damn, i tried starting it and worked out what was wrong

ok now when i start it it fouls the bottom plug (is that no 1?) its wet and black but not milky, it smokes a lot blue smoke and black smoke, the air box had about half inch of fuel in it , it runs faster then it should do on tick over , if i clean the plug it runs smoothly for a short time then it smokes , if i leave it it can clear and run smoothly but not for long , i did a ct it has 125psi on the top two cyl the bottom one has 120 psi

its not spark i changed the coil packs over and still the bottom plug fouls,

could my battery leads of damaged sth? could it be the reeds (fuel in the air box?)

what would you do next to diagnose this ?, ive no idea if this came to me with this problem but it seems like it ticked over ok when i first stared it ,
im a retired land rover mechanic by trade these big outboard are alien to me , and help very gratefully received

kind regards
 
i should of added i took the carbs off stripped and cleaned they seemed ok, you mean the float level? the float valve looked like new and no dripping of bottom carb,
ill take another look if you think its worth it ?
 
hi sorry for delay ive got the engine running, the timing was way out , i managed a maiden with the engine wow fast on my little mariner 16gt and its running like a bag of lumps

compression is even now , but ive a persistent miss now,
and it is so thirsty!! i need shares in BP, im going to do the fuel pump a service it has very old looking diaphragms on it so a outboard tech told me ,

could it be over fuelling if they are holed? by the fuel going in to the crank case?

there was a weak spark on the top cyl, so ive put a new cdm on it but the miss is still there , im going down friday to have another go
 
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