Engine smoking

[skibumtx]

Need some help running down this issue. I have a 2006 Launch 21V with the 325 engine. When out on the water, I see a little bit of smoke coming out of the exhaust, can't tell what color may be more white than blue. It does not smell like gas or oil burning. When surfing behind the boat, it irritates my eyes. There is also a black scum on the back of the boat right at the waterline when I pull it out of the water.
The cap looked really bad, all the plugs were black and dry with carbon deposits, so I replaced the plugs, oil, cap and rotor this weekend. Looked at the valves on one side, and did not see any issues with the seals. Ran it yesterday and just pulled a couple of the plugs, I'm back to black carbon deposits after one trip out. Any ideas on what to check?
Don't think there are any adjustments that can be made to the fuel injection? I do need to do a compression check. It runs fine, just would like to be able to surf.

[cadunkle]

Sounds rich if it's a whiter/lighter color. Darker would be oil and mostly likely coming from valve seals but confirmed they're fine, and oil wouldn't irritate your eyes. I would say it's normal steam from the exhaust but that wouldn't irritate your eyes either. So yeah, likely rich when coupled with the dark plugs.

I'm not up on fuel injection aside from the basics as I don't own any fuel injected vehicles and generally avoid working on them. Firstly, you can clean the throttle body and IAC valve, if they're dirty or plugged up they can restrict airflow possibly resulting in a rich mixture, but they would only affect idle. Get some throttle body cleaner and spray it around in the throttle body and on the butterfly, wipe up with a clean rag and spray until the blakc/oily residue is all gone.

Aside fomr that, my suspicious would be a bad temperature sender. Is your temp gauge working properly? Does the temp gauge use a different temp sensor than the fuel injection (often EFI systems have two senders)? Go ahead and check the resistance on any temp sensors you can find.I don't know if the GM temp sensors are still the same spsec as late 80s/early 90s but would suspect they stayed the same. Resistance is as follows...

241 ohms at 194*
332 at 176*
467 at 158*
667 at 140*
...
2238 at 86*
2796 at 77*
3520 at 68*

Whether those are the exact resistance for your model year I'm not certain, but if you watch the ohms on the sensor used for the EFI you'll see a LARGE difference in resistance from cold to operating temp. There should be no doubt as to whether the sensor is working properly. If it is not, the fuel infection will add extra fuel as it thinks the engine is cold. The result would be similar to a choke sticking closed on a carb.

[skibumtx]

Temp gauge seems to be working correctly, ie is low when cold and moves up to normal op temp when out on the water, but I'll check it when we go out today. I forgot to mention earlier that the throat looked a little dirty, so I cleaned it before going out yesterday.

Thanks for your response, I'll post this afternoon how things look.

[pwildbil]

Im no expert...but this does sound like a rich condition....I know cars but not boat EFI systems.....but temp sensor, tps(throttle position sensor) sensor, and MAF(mass air flow) sensor would all cause a rich condition on a car....contact cleaner works good for cleaning all the above just make sure you dont touch MAF sensor with your hands. Something quick for you to look at! Also make sure your TPS is tight and not loose!!

[Seabeejamie]

check your flame arrestor also...a choked flame arrestor can cause that. I had the same problem at one time, but mine is TBI, it was the Idle Air Controller on the TBI plate. I believe you have MPI....does it have an IAC? don't know how to check it, someone suggested it may be my problem, 20 part...too easy to change.

[skibumtx]

OK, the temp sensors are fine, both the gauge works and the ohm meter checked out. Still have a small amount of smoke and the plugs are black with carbon.
I have cleaned the flame arrestor tonight. The MAF sensor is actually a MAP sensor. Can you clean it? Picture is attached. Found a new one for $45.
What is an IAC?
It runs great, just messes up the plugs and the exhaust burns my eyes.

[michael hunter]

It definitely sounds rich. Does it have oxygen sensors? With out a scan tool you are guessing at best. This one might be best to take to the dealer for diagnoses.

[Seabeejamie]

IAC is idle air controller...you have muti-port injection. you don't have it. The MAP is the Manifold Air pressure sender...probably not it. I would have to agree with Mike....if you have O2 sensors on your exhaust, these are a high failure item (same as in a car). run 50 a piece for a car, so you may want to have diagnostic check run. Sure do wish my OBD-2 worked on boats!

[pwildbil]

Yeah if you have MAP then you are dealing with a speed density EFI system....No MAF or IAC's ...make sure to Check all your vacuum lines too....