1986 90hp Merc wont start

[mnmfors]

Hello everyone<br /><br />I have no spark on any cyl. <br /><br />I have a fairly new stator.<br /><br />Brand new starter (spins real fast) <br /><br />Fairly new battery<br /><br />I have another merc that I swapped the coils (I am certain they work good)<br /><br />I also swapped stators, but I put the new one back on. <br /><br />Next I suppose is the switchboxes? Are these the two boxes to the right of all the coils?<br /><br />I am also trying to fix a charging problem (another thread) Schematic was helping me, and I need a running motor to test the system. Maybe it is related, I dont know.<br /><br />Thanks in advance for any help.

 

[12Footer]

Re: 1986 90hp Merc wont start

The wire bundle will have a black with yellow stripe wire. On older models, this is orange.<br />But I think yours is the black/yel.<br />remove this wire at the switchboxes. Note, you will have to be in a position to cut the fuel supply, as it will be the only way the shut down. But this test elliminates everything outside of the engine (ign and lanyard switch,wire harness ect). Sometimes, this unhooking will make the engine run on half. This would indicate a shorted switchbox,as with a shorted switchbox hooked-inline with the good one, it shuts-down the good one.

 

[jimbusch]

Re: 1986 90hp Merc wont start

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[mnmfors]

Re: 1986 90hp Merc wont start

Thank you 12 foot,<br />Sorry, I forgot to mention that I tried unhooking the kill wire (black w/ yellow stripe)<br />I accidentally posted this question twice, I stated on the other thread that I put a hair dryer on all of the elec. components and it fired right up. Any idea why this worked? I didnt think they were wet, just tried it for kicks. Is it common for condensation being built up on the old 3 piece hoods?

 

[12Footer]

Re: 1986 90hp Merc wont start

NP, about the double post,because I've found I rarely get off the surface page when I logon here.I tend to answer only "zero-reply" posts, because everyone deserves at least some help, even if it's not much to offer them...So no doubt, I overlooked the original.<br /><br />But to answer, yes,it's common in Fla's climate, to have moisture get into everything. These older mercs have great sealing,but it doesn't matter...If it's marine,moisture is a big problem,regrdless of maker. What did the trick when u hit it with the hair drier? CD box? <br />Highly suspect all terminal connections.In this hunidity, they corrode,and you'd never know it.<br />Pull them all, one at a time of oourse, and wire-brush them shiny. The dremmel is the tool of choise,with a small brass rotary brush attachment..Nothing I've used comes close to the speed and end-result. Also, all those "auto-type" bullet connectors...The female end will tend to vibrate open just enough to give you fits. A pair of pliers and a light touch can be used to re-stress them, or close them-up a bit,making the connection nice and tight after you clean them.<br />It really can be as simple as that, but sometimes, when moisture gets-under the epoxy of the CD,switchbox,and gets onto the board, it corrodes the circuit paths, and kills them.<br />Mr Schematic had posted an in-depth thread here on actually REPAIRING switchboxes by carefully cutting,grinding,or peeling-back this ecapsulating material,fixing the problem and re-pouring it.

 

[mnmfors]

Re: 1986 90hp Merc wont start

I hit all the electronics at once, so I dont know what did the trick, I will do as you said, clean all the poles, and hopefully this will cure it....now for the charging problem....thanks again<br /><br />By the way, I have been trying to lighten the load of the experts on this forum, by answering some of the obvious questions, and I really appreciate all that you and the others do for this site.