1989 Yamaha 9.9HP Fourstroke problem

[G-ROD]

This motor runs like a top for a while and then acts like it loses spark and shuts down, just for a second then resumes running great. This will happen about every 1/4 to 1/2 mile. It never does it long enough to stop the boat.
It starts on the first pull every time, it idles all day easily and runs great until this problem occurs. It does this everytime I take it out. ANY help and advice would be greatly appreciated.

 

[G-ROD]

Re: 1989 Yamaha 9.9HP Fourstroke problem

Anybody??

 

[gss036]

Re: 1989 Yamaha 9.9HP Fourstroke problem

I've got a Honda doing almost the same thing, only very seldom does it die, it just goes chugh-chug and then takes off again. It will beinteresting what you find. I will keep watching the post.

 

[rodbolt]

Re: 1989 Yamaha 9.9HP Fourstroke problem

first thing ya gotta do is figgure out which part your missing,fuel or spark. easiest way to to this is to attache a peak reading meter to the coil primary and run it, if the primary voltage stays stable when the engine misses its fuel, if the primary voltage dips at the miss its ignition.
once you isolate which engine subsystem is failing its rather easy to fix.

 

[gss036]

Re: 1989 Yamaha 9.9HP Fourstroke problem

I appreciate your response, on my Honda, about the only time it has done is when I am on the saltwater, I have never been able to get to do the chug-chug thing on a hose. Even on the water is only does it for 15-90 seconds and then stops and then will run great for the rest of the day, maybe 6-7 hours. What is a peak reading meter? Ok, I googled and got on the CDI site and read about the meter. Don't have one, just a cheap multi-meter.
Any ideas?
I don't mean to high jack this thread but you have been really helpful in the past on my big Merc.

 

[gss036]

Re: 1989 Yamaha 9.9HP Fourstroke problem

I guess there is no one willing to offer a suggetion for either engine or than Rodbolt.

 

[G-ROD]

Re: 1989 Yamaha 9.9HP Fourstroke problem

Thanks rodbolt. I'll figure out which it is after I borrow the tool. My guess is spark.....

 

[rodbolt]

Re: 1989 Yamaha 9.9HP Fourstroke problem

kinda what i would lean to,

 

[G-ROD]

Re: 1989 Yamaha 9.9HP Fourstroke problem

rodbolt, it was spark....................................changed the oil and noticed it was low, just a little, but enough to trigger the low oil cutoff!! Changed it, made sure it was FULL and took it on the water. It is fixed and runs excellent.
The guy I bought this boat /motor from told me it has had this problem for 3 seasons!!

 

[rodbolt]

Re: 1989 Yamaha 9.9HP Fourstroke problem

see how easy it is
the motor was trying to tell you it was sick.
I had all but forgotten some of the early tiny mite 4 strokes had an oil level sensor
but some years back I made 150 bucks by adding a qt to a blow boat kicker .

 

[gss036]

Re: 1989 Yamaha 9.9HP Fourstroke problem

G-ROD, is that little Yammie still ruinning ok for you?

 

[G-ROD]

Re: 1989 Yamaha 9.9HP Fourstroke problem

Well no........... Water getting in lower unit. I can't find any cracks anywhere. I changed the drive shaft seals, the prop shaft seals and the o-ring to no avail. Still not fixed. But other than this new problem, the engine runs great. It's at the shop now, hope to get it back next week.