Fuel or CDI box problem???

[BB46]

I have a 1986 Yamaha 90 hp outboard. I got it used. Put a jet pump on it and tested it today. It failed miserably.

It started fine. Ran slow speeds well. But when rpm's came just a little off idle it faltered bad. Missed, spit, backfired, and shook bad.

My first thought was plugged carbs, bad filter of pump. The back fire is getting me thinking it may be ign box problems.

I cleaned the filter unit but it looked OK when I took it apart. The pump looked good inside too. I ran it and tried pumping the hose bulb just to see if I could make a differance but that didn't help.

Do those boxes go out much? Do they control the timing? That's what the back fire acted like. A timing issue.

Any help??? PLEASE

 

[rodbolt]

Re: Fuel or CDI box problem???

its rare to9 have a CDI failure. check the muffler on the jet unit carefully for rust holes.

 

[BB46]

Re: Fuel or CDI box problem???

Hummmm,,,,, Hadn't thought of that. The jet was almost new when I got it. One of those deals when the guy didn't like the power loss and switched back to prop.

Also I didn't mention that also while running I sprayed highly flamable stuff into each carb looking for a differance and that didn't help either. That also leads me to believe it may not be a fuel problem.

I got this used from a dealer. Also leads me to believe that somebody traded it in for a reason. I was thinking it was because thte lower unit had broken aluminum blades. That may just have been part of the reason. Still,, I got it for very little $$$. Even if I have to put a cdi box on it it would be a good deal for me. Just don't want to throw parts at it. They are too expensive.

 

[BB46]

Re: Fuel or CDI box problem???

Also, is there a low oil rpm limiter system on this old of a motor? I have an empty tank and am mixing 2 cycle oil into the gas. Would that make a differance?

Any other ideas? I have no manual.

 

[rodbolt]

Re: Fuel or CDI box problem???

if the low oil level switch has not been disabled then yes it will go into RPM reduction.

 

[BB46]

Re: Fuel or CDI box problem???

To disable could I just put oil in and plug off the outlet hose? That should give that sensor in teh talk some oil. Or is there a flow sensor somewhere also?
Thanks for the info. Hope that is my ownlt issue.