mercury 90 starting problem

[foxrockport]

I just purchased a used mercury 90 hp inline 6 not sure about the year but it has the external tilt/trim motor. The motor cranks but won't turn over, seems like there is no spark, is there somthing obvious I am doing wrong, the motor ran well about a month ago so seems like it must be operator error, please help

 

[stratodoc]

Re: mercury 90 starting problem

I'm in exactly the same boat. My 90 HP Merc is an '87 or an '86. It wouldn't start today (It ran last week). It turns over but it seems like it has no ignition. I had a trickle charger on the battery and I fear this might be a cause. I'll try tomorrow to get it started and let you know what happens.

 

[dvchristoff]

Re: mercury 90 starting problem

I had the same problem on a 650 Merc. No spark to any plug. Turned out it was the switchbox. Replaced with a used one and it started right up and runs fine again.

 

[thedeluge]

Re: mercury 90 starting problem

I am having the same type of problem with my Merc 90. No spark but it ran fine last time i had it out. My question is: will a switch box go out slowly over time or just like that it quits working. Any help is appreciated.

 

[stratodoc]

Re: mercury 90 starting problem

Hello again. Worked on my Merc 90 today with good news. The starter and the (+) battery terminal were getting hot, and it appeared to have no spark (even with short starting attempts). I cleaned up the corroded terminals and followed advice found on this ring about not using starter spray. Instead I cleaned up the plugs and put a little gas/oil mix in the cylinders. I made sure there was plenty of pressure in the gas bulb and she fired off beautifully. Good luck.

 

[scmillar]

Re: mercury 90 starting problem

my 1978 90hp turning over great but will not start. fresh fuel has spark. where is the switch<br />box you're referring to. Also behind the fuel pump<br />there looks like a vac line 1/8 bottom of power head, line coming from the top of power head. Is this a vac line?