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Hi,
Apologies if any of the terms I use here are not right.
I have a 1988 Yamaha 50D that has an issue.
It started of by stalling at idle or really low revs.
I stripped and cleaned the 3 carbs but this didn’t fix it, and it started stalling even more than previously.
I took it to someone who is good at repairing Yamaha’s.
He noted that the primer bulb was faulty, and that the top carb had a fault. When he covered the top carb intake, the engine ran much better. He is really busy, and I wanted to try and get out as soon as a possible so when he took a while to source a carb I took the boat back with the idea of ultrasonic cleaning them.
He did say the outboard had really good compression, and was definitely worth fixing.
I completely stripped all of the carbs and cleaned in the ultrasonic cleaner. I also fitted carb repair kits to all of them, including new floats, gaskets, needle, idle screw, and the three washers that sit under the top plate.
when I retried it the issue remained. on looking at the top carb the only issue I could see was the throttle disc/butterfly was slightly different to the other two, it didn’t seal as well when closed and looked slightly damaged.
I sourced a replacement and at the same time redid all of the internal fuel pipe, installed the internal filter that was not there originally and replaced the fuel pump, so everything up-to the carb was new.
when I fired her back up, she now runs, but still misses at idle, and stalls if throttled back too far.
I put a can of Powertune through her, and the replaced all of the plugs with B7HS-10’s. i checked the gap on them all. I did notice the plugs were an odd mix when I took them out, the lower two were B8’s rather than 7’s.
I have done what I believe is a sync, by ensuring all three butterflies are closed before tightening that screw.
I have adjusted the idle screw to what I believe it should be 7/8ths of a turn out from seated.
There is a video of her running here, she still has a misfire.
I run her on E5 petrol (which is supposed to be E0 where I live), and there is an external water filter which I installed. When I first used this I had to remove it whilst out as the outboard didn’t seem able to pull fuel through it. I have reinstalled it now, with the fuel bulb in the right place and it all seems to work ok now, but it wasn’t in place on my last trip.
thanks for any help.
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