BT6 mid speed black smoke

[Christopher Spangaro]

In May I bought a Riviera 3300 with twin BT6 engilo o wanes. 1993 but only 10001000 hours on them. Had a pre purchase mech survey and oli analysis. Clean bills of health apart from corroded heat exchangers which were replaced with new. Covid arrived and we could not go to the boat for 4 months.

On first use after the port engine would initially not rev past 1500 and blew clouds of black smoke at that speed. Cleared after a few minutes but since has failed to reach WOT by 200rpm. Hull and props just cleaned, and on advice replaced that turbo.

Since still fails to reach WOT by same margin, steams a grey/black steam around 1800 to 2000 rpm which starboard does not although both steam at WOT.

Bit baffled. This all started with layup. Has symptoms of too much fuel or insufficient air but clearly not turbo. Will try swapping intake ducting with other motor to exclude that but otherwise a bit stumped. Engine runs at normal temp at all speeds

Advice? Thanks

Chris

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[Christopher Spangaro]

First thing I did is slip the boat, clean and antifoul with propspeed apied to props and shafts. Same before and after slipping. So clean
Properly clean

[Woo]

After 4 months layup mate, you say it’s now got a clean bottom and props, but HOW clean are they really?

It really doesn’t take much to really knock them around, even remnants of coral worm on running gear can really affect them because Riv propped them very close to over-propped when new, and boats only get heavier.

[Christopher Spangaro]

The engines are BTs so no after cooler. Sudden onset after long layup and props and hull cleaned, new turbo and air cleaner carefully checked. Only makes 2400 at WOT. Starboard engine makes 2600 as they both did pre layup.

[Steve Lewis]

Are these 6BTA-330/370’s? What is the history on the aftercooler maintenance? Since you indicated the HX’s were replaced, one might surmise that the Aftercoolers need servicing or replacing. Did the boat make rated RPM +5% at sea trial?

https://www.sbmar.com/featured-article/understanding-low-power-troubleshooting/

Black smoke is insufficient air. My first set of troubleshooting would be the entire intake track. From the air filter all the way to the manifold. That means the air filter, turbo, piping to the Aftercooler, the AC itself and the piping after that.

There are a couple of Riv owners on the forum from your area so hopefully they will chime in and give some top tips from their experience.

[Author]

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