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To help tune our carbureted engine, we fabricated aluminum spacer blocks to mount a wideband oxygen sensor in each cylinder bank
as close to the exhaust ports as possible. The sensors will feed an air-fuel meter which will indicate if the air-fuel mixture
is rich or lean. The spacer blocks are prototypes for an automotive TBI to marine conversion kit that we've been working
on. We'll have more on that project as soon as its up and running !
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We fabricated a set of exhaust manifold spacers from 1-1/2" thick aluminum stock.
(16-MAR-2011)
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The original allen head cap bolts were replaced with studs.
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The spacers will be drilled and tapped to accept a wideband oxygen sensor.
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The sensors are only installed when we wish to check the carburetor's calibration after we've made jetting changes. A stainless steel
oil pan drain plug is installed when the sensors are not needed.
(16-MAR-2011)
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Sensor fitted to the first cylinder bank ...
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... and the second cylinder bank.
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The air-fuel meter can monitor each cylinder bank individually or can provide an average for both cylinders. Averaging both sensors
at 2000 RPM gave us this reading. Our jetting is in the ballpark, so we'll log our next run
under load and cruise conditions and try our next setup. The meter will store up to 25 minutes of data in
the dual sensor mode. This tool really takes the guesswork out of tuning a carburetor !
(25-JUL-2011)
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The spacer blocks added 3" to the overall width of the exhaust system, so while we were at it, we replaced the 36" long runs of
3-1/2" wet exhaust hose with aluminum pipe. We cut the Glenwood 3-1/2" exhaust elbow flange and welded on 4" aluminum pipe
stubs. The aluminum 4" OD vertical-drop 'S' pipes were cut, rotated, fitted and rewelded. The pipes were detailed
and sprayed with DuPont etching primer and topcoated with Imron silver metallic paint.
(24-JUL-2011)
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Space is at a premium in this boat !
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We didn't have space for mufflers, so we installed Gibson Transom Mount Power Tip mufflers. The silencers reduce decibel ranges and
surpass the 88db limits required by the California SAE J2005 Motorboat Sound Law without compromising power. Click the photo
for a higher resolution image.
Click here for silencer specifications.
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