5.0L OMC won't idle

[Droopy]

OK, I need to figure out where to go from here. I've got a 1988 Bayliner 2150 Capri with an OMC 5.0L in it with a Rochester 4BBL carb.

While troubleshooting the choke a couple weeks ago, I noticed it looked like the starboard jet wasn't, umm, jetting. A couple quick shots of carb cleaner fixed that. Now both jets look identical when pumping the throttle. I also changed both the fuel/water filter and the little filter in the carb inlet.

The motor is tough to start cold (bad choke, waiting for parts to convert to electric) but has been since I've owned it. Prior to messing with things, the boat ran fine once warmed up as well as idling just fine. Now, it will not idle even when warmed up. Starting at about 1600 RPM, it starts bogging down. A shot of throttle will keep it running smoothly above 1600, but nothing below.

Assuming that a previous owner "fixed" the clogged jet by messing with the idle mixtures, I ran both screws in all the way, then backed them out 3 3/4 turns per the service manual. Still does the same thing.

I've stopped here hoping for some advice before I mess with so many adjustments that I just screw things up more. It does run strong above 1600 on the water...

Thoughts?

John

 

[RIDEPATE]

Re: 5.0L OMC won't idle

I'd pull it off, soak, and get a kit.

 

[Droopy]

Re: 5.0L OMC won't idle

Yeah... I've got a rebuilt carb coming in the mail (they originally sent the wrong one) and I'm hoping to get this running enough to safely take the wife and kids out to go tubing in the interim...

 

[Droopy]

Re: 5.0L OMC won't idle

OK, some followup and request for advice... Although, after you read this, I'm afraid the advice will be to move this thread to the SHT forum...

I rebuilt the carb on Monday. My first rebuild and it went smoothly. I was a little surprised that the carb was in as good of shape as it was. Dirty and all, but nothing spectacular. Reinstalled, and now the engine runs down to about 1200 rpm, but still won't idle... Was chatting with a guy at the autoparts store, and he said it sounded like a problem with the vacuum advance. (I know I don't have a vacuum advance on this). It got me thinking about air leaks tho. I decided to take of the intake adapter plate (the thing between the intake manifold and the carb) and replace the gasket below it. I then proceeded to drop the last bolt down the intake manifold... Doh!

I couldn't find the bolt with a magnet or anything else, so I decided to go out, get new gaskets and seals, and remove the manifold. (Figured this would eliminate a leaky manifold at the same time)

That went surprisingly smoothly, although I had to relearn how difficult it can be to reinstall a distributor...

It started with a bit of difficulty, but once I got the timing from about 50 - 70deg BTDC back to 10deg BTDC, it runs ok. (Seems to run a LOT smoother with more advance than that?!?!)

Now, it will *almost* idle with the throttle in neutral (around 800rpm.) It's supposed to be 500 - 600rpm, but that's supposed to be measured in the water in gear. Approximately what RPM would be right sitting in the driveway running on the hose? Anything else I should be looking at?

Thanks,

John