Yamaha Pro 50, ironing out the kinks

[TownsendsFJR1300]

The issues im having sound a lot like this thread: http://www.yamahaoutboardparts.com/f...h23661-p3.html

Which might confirm my suspicion of the bad prime start diaphragm. I wish I knew what their final solution was though.

Heading out soon for a cruise, see if things run better. Ordered the diaphragm and gaskets for the fuel enrichment, when those show up I will post if any results. Wish I had a timing light to confirm timing and a leakdown tester, it'd be good to rule out any issue, but compression was good so fingers crossed. I really think its getting too much fuel.

I agree, but the spark plugs, if their soaked, black sooty, etc, will help confirm your suspicion.

[Pat Gidley]

Alright so the saga continues. Went out for a rip, still doesn't like to idle, but managed to get going with the fast idle lever. 1000-2000 rpm is a bit rough but not bad. 2000-5000 is very smooth. It'll just make it to 5000 with careful trim adjustment. Ran at high speed for a bit and checked the plugs, nice and brown - ever so slightly wet.

Slowing down to *****ing speed, it gets a bit rough and eventually will conk out. Might cough a few times but always stalls. After stalling, plugs are wet. Getting going again, it bogs and wants to stall, but if you keep on it it eventually clears up and takes off.

After clearing up, I can slowly throttle down to 1000 and it runs ok, doesn't stall just the occasional knock. If I try to adjust the idle speed screw to keep it above 1000, when starting the rpm takes off really high, like 4000 and then comes down, so that is no good.

So when the fuel enrichment parts show up, I'll see if that clears it up. The other thing I could possibly try is installing a float bowl from a carb without the fuel enrichment and see if that clears things up.

Any other things to check as sources of fuel loading?

[TownsendsFJR1300]

i think your fuel pump works off vacuum with a diaphragm (but aren't positive) bolted to the block;

1990 50ESD Yamaha Outboard FUEL SYSTEM Diagram and Parts

If that diaphragm is leaking, fuel can get into the block. Look at the break down of the fuel pump, the internals, etc..

[Pat Gidley]

Fuel pump should be ok, I swapped in a newer one and it made no difference. I guess they coil ups both be bad - stranger things have happened. But should be able to rule that out.

Man, you gotta see the amount of soot coming off the engine with that ring-free. Black oily looking crap coming out of the spark plug holes, and the prop is all covered in it. I'm gunna run a bottle through my snowmobile this fall.

[TownsendsFJR1300]

Fuel pump should be ok, I swapped in a newer one and it made no difference. I guess they coil ups both be bad - stranger things have happened. But should be able to rule that out.

Man, you gotta see the amount of soot coming off the engine with that ring-free. Black oily looking crap coming out of the spark plug holes, and the prop is all covered in it. I'm gunna run a bottle through my snowmobile this fall.

Yep, I told ya that RF works good...

Re the Fuel pump. Maybe pull the spare one apart(if you haven't already) and peek inside at that diaphragm. That the only other thing I can think of besides the carbs...

Hopefully its just the enrichment system causing the issue

[Pat Gidley]

I was poking around last night and decided to check out the thermostat - was going to swap in the one from my failed motor as it wasn't very old. To my surprise, some monkey had removed it entirely. I don't think that would be enough to cause the issue with idle, but its probably not helping my issue, especially since I'm running in some very cold water. Also explains why there was so much carbon.

Enrichment system gasket should arrive monday. I'll swap the solenoid while I'm at it, just to be sure. I can test out the spare beforehand. Do they open at 12v?

Now, I could go and test it out and see if the thermostat is the fix, but I'm wary of that leaking gasket. Wouldn't want to run the #3 carb rich and cook a bearing, so since parts are on their way I'll just hold off. Anyways, enjoy the weekend.

[99yam40]

That is not a solenoid it is a heater unit.
It receives voltage from the lighting coil while motor is running to heat up a wax pellet inside that pushed the needle down into a seat to turn off the extra fuel for cold starts and warm up of motor.

You can put 12 volts DC on it for a few minutes and see if it extends as it should, specs are in the service manual along with the testing procedures

If you turn the red lever to the closed position it will turn off all extra fuel so it will not be dumping while motor is already warmed up if the unit is not closing it off itself

[TownsendsFJR1300]

I don't know why there guys pull the thermostat's...

Have a Happy 4th too!

[Pat Gidley]

Hey 99Yam

I think on mine it is a solenoid - later ones had the heater, maybe due to issues with these. Wonder if the heater can be retrofitted? Anyways, here is what I have, part number 41.

1990 PRO50LD Yamaha Outboard CARBURETOR Diagram and Parts

I'm guessing it operates the same and may be being held open due to the cold condition and lack of thermostat. If would make sense then that I can get a nice clean idle in the driveway, but not on Lake Superior.

[TownsendsFJR1300]

Sure sound's / reads like a solenoid....

[Pat Gidley]

Good call, I'll meter it and see what voltage it engages at. Might tell me whats happening too.

[99yam40]

i wonder if Yamaha is up to it's regular tricks and miss labled some parts

[TownsendsFJR1300]

I think we're on the same page as to what "part" we're talking about which is ALL that matters...

[99yam40]

I think we're on the same page as to what "part" we're talking about which is ALL that matters...

Not really as a solenoid when energized is a electo magnet and instantly moves the core and rod.
the heater unit slowly heats up and caused the wax pellet to expand slowly to push the needle out slowly
they are tested differently

[rodbolt17]

insert the knife between the second and tird rib.
chase the easter bunny.

you have a fuel system issue.
simply disassemble it, repair it.
go play.