We went through some similar fault finding and after changing out the carb and a bunch of other parts, we finally determined the real problem was the fuel pump. Your full speed scenario would support this.
If it's not this then perhaps you will need a new carb, but if the dealer is doing the work have him test this theory but not charge you for the carb if it doesn't remedy the problem. The real point of going to a dealer is that they should actually understand their engines and be able to trouble shoot them, not just change out parts. If your dealer is incapable of this, then find another.

 

Thanks Capta, I was also thinking the same thing. Either there is something particulating inside the fuel delivery system post-filter, or the fuel pump is starting to go (which may also be delivering the particles maybe). I guess I'll find out this week when I head down. I'm hoping to fix it for one last sail before the inevitable haul out and winter storage coming up. Although I've loved the simplicity of working on an outboard vs. an inboard (for a small boat), and absolutely love the control an outboard has for docking, the next boat will have an inboard and be diesel. Hopefully removing "carb ghosts" from the list of breakdowns (and most likely adding something new instead!).

 

Wow, Guyfromthenorth it sounds to me like you do all the right things for this outboard.

Capta probably has it, but before I'd buy anything I'd clean that carb and even though you are meticulous with fuel, I'd toss all the old fuel and start again. I've had re-occuring problems like this from a bad tank of gas.

Good luck...

 

Good call, maybe I'll filter it out and see if I catch any particles (for my own knowledge) and use the filtered stuff in my truck, it doesn't seem to be as picky. That'll be one less suspicious bit, it's been 2 years so the tank is most likely due for a good purge anyways just to be safe. I'm usually fairly meticulous about fuel contamination because I live in a rural area and work a job that requires me to be in very remote locations relying on small engines. Things like power pumps, chainsaws, ATV's, -boat motors-, and snowmobiles. If there's a way to contaminate fuel I've definitely experienced it at some point lol. :svoilier:

 

At what point do you just replace the 30+ year old outboard with a new one? I am a mechanic, so I deal with stuff. At some point, when you are paying retail, it makes more sense to just go new.

 

Well, at this point I've invested, not counting my own time since those dollars are imaginary, about 1000$ total. A brand new Honda 9.9hp 4stroke in my neck of the woods runs just over 4000$CND. To buy a used honda of the same pedigree as mine will run about 1000-1500$, but then you again own an "old motor" with the same or more problems. It doesn't make sense to buy a new motor at this point. If I had a blown bottom end, or a seized crank maybe then it would be a consideration, but even then it would be a used motor. Unless I planned to sail this boat the rest of my life (which I don't), and completely restore it, a new motor would be worth as much (or more) than the actual boat.

Carb problems are small but frustrating, this old honda has life in it yet.

 

I will bet that ethanol is the enemy that sabotaged the carburetor on your motor.
I suggest that you do the following;

• draining and throwing away the old fuel that is in the tank.
• remove the carburetor
• take the carb apart and remove the float and the jet needle
• clean / degunk any orifices - including the float bowl inlet - with a sewing needle
• carefully inspect the float needle valve for gunk/corrosion
• use some 3000 grit sandpaper/emery cloth and wipe the jet needle until it just *starts* to shine
• put everything back together
• add FRESH fuel from a MARINA
• adjust the carb
• start

 

That's a good point, I've heard ethanol can gum stuff up especially in small engines but generally haven't run into an issue with it yet up here. The "regular" fuel I buy for the boat guarantees "less than 10% ethanol by volume", but I guess that isn't 0. I suppose I could switch to premium as it contains 0% ethanol. The real issue I run into with fuel in my area is the old "lesser of two evils". Gas is expensive, premium is about 5.85$ a gallon with the current market, it goes up over 6$ regularly during the summer. What that means is very few if anyone buys the premium and I know a friend of mine who has got stale or wet gas more than once from a premium pump because the mom and pop gas station doesn't flush fresh stuff through often enough. It ends up being safer to buy regular and deal with the ethanol content than risk rotten premium. The few times we use premium are in high rev snowmobile engines and the Ninja 636. Maybe I need to be buying my gas in the city and shipping it back to the boat so I can feel the premium fuel has a better chance of being fresh.

 

I own an auto repair shop. I have old timers come in who tell me how they miss the good old days when they could work on their own car. I ask: back in the day when you changed points, condenser, and plugs twice per year? I then tell them about a regular customer of mine. He came in one day with a misfire in hid Toyota Tacoma 2.4L 4 cyl. I suggested we start with a set of plugs. It turned out to be one of the individual coil packs, but I took the ORIGINAL PLUGS out of his engine with 248,000 miles on them.

 

From the perspective of age, I'd follow your instincts about 'particulation' of the surface of most all 'plastics' components of the engine that come in contact with the fuel.
Particulation is a renown source of contamination in the biopharma and ultra-pure chemical industries and is age dependent of the materials. Especially with the change from straight gasoline to mixtures of ethanol (with its accompanying water) and gasoline such problems could be worsened with increasing age.
The suspect material for degradation on a macromolecular level - too small to be seen on a eyeball basis ... and in decreasing order of vulnerability-: nylon, polypropylene, Delrin, BUNA and neoprene rubber, those small in-line fuel filters !!!! .... all subject to 'hydrolysis' - a breakdown of the long chain molecules, especially when in contact with water. Most nylons (even modified and 'stabilized' nylons) when in the presence of water will begin to readily particulate as early as six months when wetted with water. Once particles are present, they tend to 'clump' together forming larger and larger particles. The tendency of particles is that the larger particles will often 'bridge' any small orfice .... a group of small particles can easily 'bridge' across and stop the flow of an orfice that is 5+ times the size of the particles.

Note: Those small in-line filters usually contain cellulosic filter material which is 'usually' encapsulated by an epoxy-like substance ... if the 'epoxide encapsulation' is faulty, the cellulosic is rapidly 'digested' then can readily particulate as those cellulose fibers 'fall apart'. At least a yearly change-out of those small in-line fuel filters is important due to the potential digestion of the cellulose materials.

For an 'old' outboard and without verification via the use of high powered microscopes, Id offer to begin to totally change-out ALL those plastic components for new: fuel hose, carburetor float, fuel tank, main jet 'rubber tipped' needle valve, in-line fuel filter, etc.

Also and perhaps more important than all of the above, just because you add stabilizer doesn't mean that you will completely insure the stability of the fuel, as the fuel from your distributor 'may' already be well past its 'shelf life'. An easy 'visualization' of fuel stability is to pour some of your fuel into a clear glass container, hold the filled container between your eyeball and STRONG white light - any haze noted indicates severe degradation (formation of particles!!!!) of the fuel. Any noted 'haze' will indicate severe contamination at below ~10µM particle size.

 

My 6 yr old 9.9 Honda OB became hard to start after 2 years. It has low hours on my dinghy and I've always used fuel stabilizer. I had the Honda dealer rebuild the carburetor and installed the water separating Racor fuel filter on my dinghy transom he suggested. I need to replace that filter every year to assure fuel flow. I try to keep the fuel reasonably fresh, too. Still, it is hard to start and requires a warm up period before I can put it in gear and accelerate the throttle. Very disappointed in Honda. Meanwhile, my 20 yr old 4 hp Johnson 2 stroke will start on 2 yr old stabilized (if you believe that) fuel. Would never use last season's stabilized fuel in the Honda.

 

No one is ever going to render the same care for your stuff as you are.

 

You're right. I took the carb off today; I sure wish I had done it myself last time as it was very easy.

Inside I found flakes in the bowl. Way too big to have passed the filter. They appear to be remnants of gasket glue from around the bowl rubber ring. Someone at some point probably tried to sneak a few more seasons from a tired seal with that junk. The dealer definitely cleaned the carb but didn't scrape that crud off the seal and piece of it (probably softened from carb cleaner) fell into the bowl and jammed my jet.

It took 2min to scrape that crud off. If I would have done the job myself I definitely would have seen that and done it. Lesson learned. She runs like a boss now though and I'm confident I can do this job on the water if needed in the future.

Pic of the bowl:

https://ibb.co/mVHjuQ