03 9.9 resurrecting an old friend - throttle problems

[fonetikal]

Finally got my dad's old boat back out. The engine hadn't run in 5 or 6 years, 2 tanks full of the worst gas I've ever seen!

I emptied a tank and inspected the hose and fittings, all look usable. Filled with fresh gas and good oil. Good to go.

Cleaned the motor up, still in great shape, super clean inside, greased all the nipples everything. Spark plugs looked good, cylinders had some oil in them, I'm assuming from when it was winterized years ago. Got spark no problem. Fuel filter looked good too. Pulled a lot, getting fuel to the cylinders, finally fired up!

Ran super rough at first, cut out a lot, as expected, figured it has to flush the old gas out. Eventually it settled down and idles pretty nice.

Now the issue. As soon as I touch any throttle it dies. If I pull the choke while it's running, I can give it a bit of gas until it gets rough again, and then when I push the choke back in I can rev it right up for a second, and then it tries to die again. Back the gas off and it continues to idle fine.

I'm excited the motor is running at all, but if I can get it working properly I can get my dad's boat back in the water for the first time since he passed away 5 years ago. Help!

I checked the fuel filter again after running it for a while and it still looks fine. I can't get the screen out, and I don't want to wreck it prying at it, but if I lay it on its back and squeeze the fuel ball, gas flows through the filter no problem. I pulled the air box and discovered there's no filter there to worry about being clogged. I have a feeling I'll be pulling the whole carb off to take the float bowl apart to clean it out. My guess is the float is probably saturated, or there's deposits clogging it up from the old gas, or both. Really didn't want to get so deep into it, is there something simple I'm missing?

Thanks!

[fonetikal]

Update:

Took it apart again, pulled the carb out, drained the bowl and took it apart, cleaned it all up, seemed to be working fine, the little shut-off pin it controls is working fine, cleaned that too. Put it all back together, no change.

[waterboy]

Had the same problem on my 25, the main jet and port were partially plugged. carb cleaner and a blast of air might help.

[fonetikal]

I thought that too, until I found I could get it to rev up full blast after choking it for a few seconds... Is there some high-speed mixture screw that could be out for some reason?

[fonetikal]

any other guesses?

[waterboy]

when you pull the choke to get it to run at top speed and you push it back in does the engine stay running at top speed?

[fonetikal]

it kicks up a lot more, with the choke out it runs super rich so it won't rev up really high, but when I push the choke back in it revs up full for a couple seconds, then tries to die again, and if I throttle down it will idle no problem forever.

[waterboy]

sounds like your idle circuit is fine so you would think it has to be something in your main circuit, did you unscrew the main jet from the float bowl and clean both the main jet and related passage in the bowl and carb? and by the way i'm not a marine engine mechanic by any means, i play mostly with motorcycles and atvs. figured i'd hang out here and learn a thing a or two so i'm probably not going to be a lot of help.

[fonetikal]

I didn't want to mess with the main jet too much, wasn't sure if I could unscrew it out of there or if moving it could damage it or throw it out of tune or whatever. Maybe I'll pull the carb off again and get in a little deeper, it's a real bitch to get one of the mounting nuts back on though...

[waterboy]

can't really screw anything up with main jet unless its stuck so bad you mess up the screw driver slot (been there done that) i hear ya about the mounting nuts, not a good place for fat fingers!!

[fonetikal]

Thanks for your help, much appreciated, I'll report back when I have time to get back in there!

[fonetikal]

Got fed up with it sitting in the shed and no time to mess with it, took it in and the guys at the shop threw it in their carb cleaning machine. Sorted. They said the "fuel pump" which is more like a rubber bubble that pulsates, was all gummed up. I work with a guy who had guessed this as his diagnosis too.

Anyway, got it back in time for the weekend and she's purring right along!