1999 GS 3.0 GSPWTR oil sheen on water in driveway after carb rebuild?

insttech1

Petty Officer 1st Class
Joined
Jun 26, 2011
Messages
340
OK got the carb all rebuilt. Put it back on, turned the engine over w/ the key for 5 seconds to get fuel going...stopped, manually pumped carb throttle until a few squirts came out, then hit the starter again. Fired up, only 150rpm low.

Tweaked master idle to get up to 700 rpm, and left it run for about 3 minutes until choke opened fully. Oh yeah--I never put the boat in gear; just in neutral.

I usually hop off the boat to ensure that my water hookup is still in place for cooling. Noticed a light black sheen on top of the water in the driveway. It does not look blue/green like drive fluid, and it does not look like unburned engine oil. It's never done that before I rebuilt the carb.

So I shut her down, ensured that it wasn't drive fluid (it doesn't appear to be), and checked all fluid levels. Engine oil and drive fluid looks OK.

So what are the possibilities? Am I possibly burning so rich before tuning the carb that the exhaust is looking like a small oil slick? Possibly burning oil? Blew a piston ring out upon first turnover after rebuilding carb?

Ideas are welcomed. I'm tempted to tweak the idle mix screws and main idle setting until they are as specified per tuning steps, then see if the sheen is still on the water...but this is concerning me...

One other thing; my float was mis-adjusted per the Holley rebuild kit instructions. I inverted the float bowl, with the center-hung float, and found it almost at the bottom of it's travel. So I put in the brand new adjusting screw, and set it to the center of the bowl while inverted, exactly per instructions.

Thanks Much!
 

insttech1

Petty Officer 1st Class
Joined
Jun 26, 2011
Messages
340
Re: 1999 GS 3.0 GSPWTR oil sheen on exhaust in driveway after carb rebuild?

Re: 1999 GS 3.0 GSPWTR oil sheen on exhaust in driveway after carb rebuild?

OK went out and tweaked idle adjustment screws in by about 1/2 turn, about 1/4 turn at a time. RPM went up, so I gradually balanced it with the main idle adjustment, then let it settle at 700RPM, and let it run for 10 minutes. No more black slick in the driveway. So I guess I was just running really rich. I'll probably have to pull the plugs and see if they're fouled up. They're new, so a quick cleaning should fix that.

Still need a bit more fine tuning with the idle mixture screws....but at least it's progress...
 

Glastron175

Seaman
Joined
Mar 13, 2010
Messages
71
Re: 1999 GS 3.0 GSPWTR oil sheen on exhaust in driveway after carb rebuild?

Re: 1999 GS 3.0 GSPWTR oil sheen on exhaust in driveway after carb rebuild?

Sounds like you are about there. Do you have any hesitation when you quickly advance the throttle? I am still fighting that problem. My next test is the timing but I have to order the timing shunt first. Haven't figured how to order one yet. Do you know if it is available on iboat web site somewhere?
 

insttech1

Petty Officer 1st Class
Joined
Jun 26, 2011
Messages
340
Re: 1999 GS 3.0 GSPWTR oil sheen on exhaust in driveway after carb rebuild?

Re: 1999 GS 3.0 GSPWTR oil sheen on exhaust in driveway after carb rebuild?

I'm not sure if you can get one here or not; I'm sure Don would know, and many others. I'm new here too. As far as hesitation, there is none, but that doesn't mean squat until I get it in the water and test everything. Besides, the final tweaks should be done on the water anyway, when the drive is just engaged, at least from what I've read. I don't plan on doing anything to mine with timing unless there is some issue on the water, and I need to do more troubleshooting.
 
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