Bad CDI question - Yamaha 1999 C90

[2barrels]

My CDI is dropping the number 2 cylinder after the motor warms up, is switched off and then sits for 15 minutes. It usually takes 30 to 45 minutes for it to come back and start running normal again. I can place a bag of ice onto the CDI and in 2 to 3 minutes it will run fine. I had an idea of installing a small 12 volt fan and timer to keep the CDI from getting hot after the engine is switched off but I am concerned that this CDI may die completely one day. This problem only occurs in the heat of the summer and never happens in the cooler months. My engine is a 1999 Yamaha C90. Any suggestions or comments would be appreciated.

 

[2barrels]

Re: Bad CDI question - Yamaha 1999 C90

I was advised by another Yamaha mechanic that this problem could be the rectifier and not the CDI. He said to remove the green wire and to isolate the rectifier. the problem is there are two green wires leaving the rectifier and one of them goes to a plug with 3 to 4 wires connected to it. Should I remove all of these wires?

 

[robert graham]

Re: Bad CDI question - Yamaha 1999 C90

Same exact motor as mine. Are you sure this is an electrical problem? Pull that #2 plug and check if it's wet/fuel-fouled caused by bad fuel pump diaphragm causing raw fuel to get sucked into that cylinder. New fuel pump about $50, easy 2 screw replacement.

 

[2barrels]

Re: Bad CDI question - Yamaha 1999 C90

Same exact motor as mine. Are you sure this is an electrical problem? Pull that #2 plug and check if it's wet/fuel-fouled caused by bad fuel pump diaphragm causing raw fuel to get sucked into that cylinder. New fuel pump about $50, easy 2 screw replacement.

I have replaced the fuel pump, rebuilt carbs, replaced plugs 3 times, replaced fuel line assy, swapped out ignition coil and trigger sensor (a freind of mine has the same engine, but I am not willing to ask to borrow his CDI). When the engine goes into failure the number 2 plug is not firing. I can see a spark in #1 and #3 plug wires but not #2. I am placing a used plug in the plug caps when the engine is in the fialure mode for testing. My Yamaha shop can not get the engine to fail in the shop so I am trying to get it resolved myself and it is starting to get expensive.

 

[robert graham]

Re: Bad CDI question - Yamaha 1999 C90

Well it sounds like it must be a temperature related electrical problem just like you say, but since it comes and goes it makes it a real tough thing to trouble-shoot and repair. I wish I could help you but electricals ain't my strong suit. Guess a new CDI unit is awful expensive, especially if you're not dead sure that's the problem. Don't suppose the problem is in that #2 coil or spark plug wire or boot breaking down when it heats up? Good luck and let us know what you find out. I'm real interested since my motor is the same, but I've never had any problems out of mine, so far, but we're dragging the boat to Florida on Thursday for some fishing and hope for good luck with the boat, motor, fish, etc.

 

[2barrels]

Re: Bad CDI question - Yamaha 1999 C90

I did swap out the ignition coils with #1 and #2 and the problem stayed with the #2 cylinder. I just ordered the CDI after further discussion with my Yamaha mechanic. He discounted it ($500 instead of $600) for me since I bought the boat from them. It is really going to sting if this is not the problem.

Thanks for your help and I will let you know how it turns out. Good luck on you fishing trip and I hope to be down there for the last week of scallop season if this new CDI fixes my problem.

 

[2barrels]

Re: Bad CDI question - Yamaha 1999 C90

I installed the new CDI and the problem I was having with not getting fire to the #2 cylinder after the engine was warm appears to be solved. I now have anther probem, the engine stalls when I put it in gear when at idle speed. I turned up the idle from 750 to 900 and it helped some but the engine will still stall. I have bought yet another set of plugs and I am going to fill up with a tank of fresh gas and see it that helps. I did not have this problem with the old CDI. The new CDI is on revision 7 and my original CDI was revision 1.

 

[99yam40]

Re: Bad CDI question - Yamaha 1999 C90

Check to see what the timing is doing and that it is in spec like the manual states.
Could be you have carb problems or compression is low
You may have to do a link and sync on it as you have started adjusting things and that is not something that needs to be done unless something is not working as it should

 

[2barrels]

Re: Bad CDI question - Yamaha 1999 C90

Check to see what the timing is doing and that it is in spec like the manual states.
Could be you have carb problems or compression is low
You may have to do a link and sync on it as you have started adjusting things and that is not something that needs to be done unless something is not working as it should

I just had the carbs cleaned, I use non ethanol gas (add Marine Stabil just in case), and Yamaha Ring Free. I checked my compression a few months ago and they were 115, 116, 112. I think it is a timing problem. I know before I added the new CDI the plugs were burning a little on the lean side, now they are almost black and oily looking. I guess it is back to the shop to have them adjust the timing.

 

[hewes90hpyam]

Re: Bad CDI question - Yamaha 1999 C90

Boy have I seen this problem floating around on a few forums - be interested to see what the adjustment will do - have you tried doing it yourself based on the specs in the book? Do you have the actual 90hp Yam book, and not one like Seloc?
Drop me an email - if you want to talk in person more - friend of mine had symptoms similar to this - changed out a lot of things since no boat shops were close by, least no good ones.

 

[hewes90hpyam]

Re: Bad CDI question - Yamaha 1999 C90

So how did the tune up go - did that end up fixing the last of your problems?

 

[2barrels]

Re: Bad CDI question - Yamaha 1999 C90

So how did the tune up go - did that end up fixing the last of your problems?

The shop I deal with suggested that I try to adjust the carbs before bringing it in after I described the symptoms of the engine with the new CDI. Basically they said to turn the air mxture screws out 1-1/4 tuns on all three carbs (they were at 1-3/4 turns with old CDI) and turn the idle up to around 900 rpms (was 750). It runs much better now and the plugs are burning light brown instead of black and oily looking. Not perfect but much better.

Next project for this engine is to add a remote trim switch on the transom since the C90 did not come with one. I am supposed to splice into the blue, green, and red wires with the switch buI I have not been able to locate them yet. Maybe I will start another thread and see if I can get some help on this one.

 

[Shoalwaterdude]

What is the C.D.I. number? Did it change mine has CU7386 and the one I just order has CU7374 they said it’s the new version

 

[GA_Boater]

What is the C.D.I. number? Did it change mine has CU7386 and the one I just order has CU7374 they said it’s the new version

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