Boat exhaust on older Supra

johnathon_03 · Newbie Joined: 04 Jul 2009 Posts: 35 City: Puyallup

So I just had my carb rebuilt on my 90 Supra Sunsport. Now it is putting a little bit of a dark film out the exhaust. Its not bad but noticeable. Is this dark film gas, oil, or possibly something else? I am thinking the carb is running a little rich kinda smells like it. I am hoping its gas and not oil or something worst! I mean the boat runs great. Holds speed a lot better and starts right up. It will idle a little fast after pulling a boarder for about 30mins or so.

I tried to tune the carb myself. Tried to hook up a vacuum tester and set the air/gas.... Couldnt really figure out how to do it. I was talking to my friend's dad about how to adjust everything.

I would really like any advice on what might be the problem and if anyone has experience with tuning the stock Holley on a 351 in older Supras.

Commodore · Ladies Man Joined: 20 Jun 2005 Posts: 11636

It's probably your fuel air mix. If you're dumping to much fuel you'll kill your plugs and that will help create the black by not getting you a good burn off.

If it's white/gray, you're burning oil. Black is typically because of fuel/air mix.

You said it was smelling rich? Did you adjust the floats in the bowls? That is the trickiest part. I worked on mine for a long time once, and 2 minutes another time. It just takes some time dialing them in.

How's the boat run other than the rich smell? Does it smoke all the time or just at start up? It may be nothing more than an older motor. Mine smokes for about 20 seconds upon each startup. But it's fine.

vette74 · Posted: Sep 21, 2009 7:52 am Post subject:

What brand of carb do you have?

Commodore · Ladies Man Joined: 20 Jun 2005 Posts: 11636

johnathon_03 · Newbie Joined: 04 Jul 2009 Posts: 35 City: Puyallup

It usually smokes the most after a hard run. It leaves black bubbly stuff on top of the water and a little bit of dark exhaust once I go to a idle. When I am running at speed the exhuast looks good and white.

The floats on my carb have to be adjusted fom inside the bowls kinda a pain in the a**. You have to bind the little metal thing and just make it as level as possible. I was told you would know about the floats if it didnt start right up after running it a little while. It turns over and starts right up.

The fuel air mix is controled by the little screws on the side right? How do I get a vacum? The little nipple you hook the vacum up to is right on the side of the carb right?

It didnt really smoke before when I would start it and ran great before carb rebuild. The motor runs great now the exhaust just worries me. Plus I dont wanna burn more gas then I have too. Craps not cheap. They need to make a hybrid wakeboarding boat!

Thanks guys
What would be another way for me to tell if it is oil or gas?

LS1_SE7EN · Criminal Joined: 17 Jul 2009 Posts: 92 City: Chattanooga

If it's black, it's not oil.

Have you noticed your boat using more fuel than normal?

kartman · Posted: Sep 21, 2009 11:07 am Post subject:

you asked for a hybrid boat, here it is.http://23e.epicboats.com/ personally, i would just set your floats. check your needle and seats. i had the same problem with a old truck i drove. would smoke black after a hard run. it was bad needles and seats. the pump was pressurizing the bowls