Yamaha 9.9 engine trouble - looking for advice

[Max123]

Carb is back together, all cleaned up. Float height was set so that the seam is dead level with the body of the carb by bending the metal tab (you can see this in the background, touching the head of the needle valve). I talked to a tech who said that in the absence of a specific height, this is the best way to go. At dead level, the float is exactly 1" from the rim and is also exactly in line with the set screw for the main jet nozzle - so I think that's right.

I'm also the kind of guy that likes a backup plan. So, I saw an old 9.9 Mariner on craigslist, selling for parts. Turns out, a 1996 Mariner is just a rebadged Yamaha with an identical carb to my 2007, so I picked that up for cheap. Now, I've got a spare carb and can mess around with both. Per ShipHappens, on the older carb, the fuel/air mix screw was uncovered and easier to adjust. I bet the old Mariner ran better than the newer Yamaha. By the time this is all said and done, I hope to have it purring and starting first pull.

Now to wait and try it next time i'm in the Okanagan... Will be a real letdown if it still doesn't run right.

 

[Max123]

Success! (Sort of).

So, brought the rebuilt carb back up to the Okanagan over the long weekend. Float level dialed in, jets 100% clean, enrichment screw cover removed and ready for fine tuning. Backup craigslist carb just in case...

Carb goes on while the engine is still on a stand in the garage and I attempt to get it fired. Absolutely no dice. Coughed/spluttered once, then refused to budge. No trick was getting it started: tape over the intake to simulate choke - nothing. Shot of fuel by juicing the throttle, nothing. Starting fluid direct into the cylinder - nothing.

Finally, after giving up I swap in the craigslist carb.

Aside from designing the world's most finicky carb, I will give Yamaha credit for one thing - this carb is easy to remove. Two 10mm nuts, disconnect the linkage, disconnect a fuel line and a vaccum line and its off.

New carb goes on, starts second pull.

The carb is still acting funky, and I suspect the low speed jet is plugged up. needs throttle to start and revs way up, won't idle below 2000rpm, and needs a good 5 min warm up before attempting to shift into gear or it stalls out. Even then it bogs down when shifting into gear and nearly stalls without a shot of throttle. At first i thought the tach was reading wrong, because it would stall at lower than 2000rpm, but that doesn't appear to be the case. Shifting at 2k is 'crunchy' and not something I like to do. Once in gear and warmed up, it idles along in gear at 1000rpm without complaint but goes back up to 2k when shifted into neutral. Flat out, its a rocket. With just myself and my 10 year old son in the old 12fter we were hitting 5500rpm and 32km/hr. I thik its hitting a limiter because It was going flat out at only 2/3 throttle.

I still couldn't figure out how to set/tune the enrichment screw. The craigslist carb is an older model, and the enrichment screw wasn't sealed so its easy to adjust. When I got it, it was fully tightened down - I experimented with trying to adjust it with the boat in gear - but no real apparent effect. Not entirely sure how it works (is fully tightened down lean?)

Anyway, its back in the garage and on the stand - next time I'll take apart/clean the the idle jet and see if I can get it purring on the stand.

 

[Max123]

For the nerds out there:

This old yamaha runs a 2:08 gear ratio and is swinging a 9.25x9-J prop (Assume this is 9" P). Fairly aggressive prop - large diameter and appears to be the highest pitch listed. At 32km/hr @ 5500rpm I'm at 12.7% slip which isn't bad because these little outboards tend to hang fairly low on the transom and drag a bit in the water.

The guy I got it from was using this motor as a kicker on a 30ft boat... definitely wrong prop for that application - but perfect for bombing around the lake on a little skiff.

 

[submerged]

On my last boat I went through 2 older yamaha 9.9s, and never got either of them to run reliably. Countless hours of frustration and several trips to Garside. These motors do not seem to like light use.

One of the issues I came across was that my fuel tank and hose needed to be replaced. I think it was sucking air, perhaps through a pinhole leak. This was especially annoying as I used the same tank on both kickers, so it might have been responsible for problems with both. The mechanic also told me these motors really don't like old gas. However this being said, I never could get the 2nd motor to run without spraying carb cleaner into the intake to get it going, then keeping it revved up. Didn't make shifting easy. This was after having the carb professionally cleaned.

 

[zurk]

lol. still at it, eh ? i would just do electric drive. the headaches are simply not worth it. the feeling of hitting a button and being propelled along silently is amazing.

 

[Max123]

No - got it running fine - tons of power and generally pretty quiet too. Still playing with the idle a bit.

I've got no complaints for a basically free motor.