Indmar TBI smoke when warm and when accelerating

[roos]

Hi,

I have a Supra Launch SSV from 2002 with an Indmar TBI 5.7 Assault that runs great, but produces quite a bit of smoke.

When first starting the engine it doesn't smoke at all.
Then when running for 5 minutes at idle speed it starts to put out a small amount of smoke.

When accelerating out of the hole it produces a big smoke cloud and then some additional smoke when running, though not that much.

The smoke looks white / grey to me. It smells of exhaust I would say.

Analysis / trouble shooting:
Engine temp stays cool, right at the 143 degree thermostat.
Only DTC I have is "Knock sensor". I don't know if this can be related, I have ordered a new knock sensor though.
Compression is a solid 170 PSI +/- 5 PSI on all cylinders.
Oil looks good, no signs of water.
I have replaced the TPS (throttle position sensor) and the Temp sensor for the ECU.

Any ideas of what might be wrong?

Weak impeller? IAC Valve? Valve seal? (Though I had a problem with a valve seal once and it smoked mainly on start-up which is when my engine does not smoke now).

Thanks!
Mike

 

[Scott Danforth]

White smoke is water in the combustion chamber. pull the spark plugs and look for a clean spark plug or two indicating water in those cylinders.

water in the cylinder from a crack in the head or exhaust manifold will pound like crazy and be picked up from your knock sensor.

blue smoke is from oil in the combustion chamber. this is usually valve seals on SBC's, however need to check. can be done with the heads on the motor with the right valve spring compressor.

 

[roos]

All 8 of them look kind of similar.
I would say these are the two outliers.

 

[roos]

Sorry. Dtc was 44. System cannot detect knock. So I think this indicates the knock sensor might be faulty.

 

[roos]

For anyone who might stumble on this thread in the future. I removed my almost new impeller that looked perfect at the beginning of the season and since then have 10 run hours maximum. There were several vanes that hung “loose”. Luckily none that broken free.

I am pretty sure I had a small leak in my raw water intake (raw water cooling in engine). So I believe the impeller sucked some air and some water. Enough water for the engine to run cool, but not enough for the exhaust to run cool.
I believe it was the gasket on my sea strainer that didn’t keep air tight. I basically re-tightened all hose clamps and removed and re-installed the strainer. Then ran engine with new impeller. After 10-15 minutes no smoke at all. And risers are cool to the touch.
Albeit this was only idle, but it has been producing some smoke and far hotter risers even at idle since start of season.