Near mint Yamaha 8B 677, 1979 - getting it running after storage - help!

[Waveydavey]

Hi folks - I was hoping you could spare some advice for an enthusiastic but very non-mechanical Yamaha owner!

I recently purchased a lovely 1980's Avon 3.10 Rover, with 8HP Yamaha outboard (8B 677, which I believe makes it the 1979 model). They belonged to a Navy chap who sadly passed away last year, and he's obviously stored them extremely carefully when not in use, as both are in great shape.

Having said that, I can't get the engine running more than 10-15 seconds, and that's with revving and trying to keep it alive (starting with choke out then pushing in). Even to get that takes quite a few pulls. I've followed the basic troubleshooting guide in the manual, and so far have:

• used brand new fuel (with the right 1:100 mix) in the external tank, the lines of which were clean and flow well
• checked the spark plugs, which were a little sooty (probably from my repeated start attempts)
• Installed new spark plugs (slight improvement in firing %age)

From what I've read, it's still likely to be a fuel issue somewhere - having ruled out stale fuel and external tank supply issues, am I right in thinking the next step is to try and clean/ check the carburettor, which might be gummed up with residual fuel remnants?

As a guide to how inexperienced I am, I barely know what a carb does - something to do with fuel and air mixing. Is taking this apart to clean a wise move for someone like me, and am I likely to end up wrecking it?

A few pics in case useful. Advice very gratefully received!

[robert graham]

It’s a good bet that the carb needs cleaning….if you’re not comfortable with your mechanical skills to do this then maybe find a good mechanic to do it….

[Waveydavey]

It’s a good bet that the carb needs cleaning….if you’re not comfortable with your mechanical skills to do this then maybe find a good mechanic to do it….

I'm working my way through a few youtube videos on it - I've tried quite a few outboard mechanics over the last week but all are super busy

[robert graham]

Maybe/hopefully you can work your way through it….YouTube can be helpful….good luck!

[Waveydavey]

Thanks! The videos have helped a lot actually...now I understand what it actually does and what the parts are, it's just a matter of making sure I put it all back in the right order

Will pick up some carb cleaner this week and give it a crack....stay tuned to hear how badly it went!

[Waveydavey]

A follow-up question if anyone can help - from the look of this engine the fuel pump is attached directly to the carb. Do I need to look into cleaning that out too, or are they less prone to gumming up with time stood?

[robert graham]

Probably can’t be too hard to disassemble that little fuel pump and inspect/clean diaphragm and fuel passages….

[panasonic]

I would order a fuel pump rebuild kit and replace those old diaphragms.

[robert graham]

I would order a fuel pump rebuild kit and replace those old diaphragms.

I agree….on a 42 year old motor it’s most probably time for a new diaphragms….

[99yam40]

plus anything hiding in the pump will hit the carb soon after cleaning the carb only

[Waveydavey]

Well, I took both apart in the end- there was a gooey nugget of oily gunk in pump, and the needle was also dirty (pics below). Cleaned with carb cleaner and put it all back together.

Pretty sure I got everything exactly as it was, but now it's dead as a doornail.

This was only an hour ago, so figure I'd let it stand a few hours in case there is some cleaner left in there blocking something up (although that stuff evaporates v quickly) :/

[panasonic]

Did you take out the jets and clean them? Small carb has very small passages that all have to be perfectly clean. You may want to bring it to a shop with an ultrasonic cleaner and have it done right...

[Waveydavey]

Did you take out the jets and clean them? Small carb has very small passages that all have to be perfectly clean. You may want to bring it to a shop with an ultrasonic cleaner and have it done right...

I took out and checked/ cleaned the big one in the left of the image attached, but couldn't see a way to get at the little one (assuming those *are* the jets)

[panasonic]

Did you get new fuel pump diaphragms? If you found that black goo in the pump and the float needle valve you can rest assured that it is gone further into the carb.

The carb needs to be completely disassembled and cleaned so each and every passage is clear. Spraying carb cleaner at it is not going to cut it.

I would also check the fuel lines on the engine to see if they are deteriorating and that's where that crap is coming from.

Looks like a very nice little engine in great shape...but will cause you endless frustration if you dont clean and inspect the entire fuel system.

[Waveydavey]

Did you get new fuel pump diaphragms? If you found that black goo in the pump and the float needle valve you can rest assured that it is gone further into the carb.

The carb needs to be completely disassembled and cleaned so each and every passage is clear. Spraying carb cleaner at it is not going to cut it.

I would also check the fuel lines on the engine to see if they are deteriorating and that's where that crap is coming from.

Looks like a very nice little engine in great shape...but will cause you endless frustration if you dont clean and inspect the entire fuel system.

Thanks Panasonic. I took it to a boatyard (Burseldon Outboards) and they cleaned it out properly - turns out I'd put the diaphrams in back to front :/

Had it out last week and runs great - EXCEPT the fuel isn't feeding through properly, and it regularly spluttered and died after about 30-40 seconds of running. After a bit of experimentation I worked out that the problem was resolved if I gave a regular tiny squeeze on the primer bulb in the fuel line. Am I right in thinking that means the fuel pump just isn't pulling through effectively, and probably replacing the diaphrams is the first place to start?