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Old 09-18-2018, 05:34 PM
Dave Neptune Dave Neptune is online now
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Gregh, you are definitely loading the cylinders, probably to much prop.

If you have a timing light you can check for full advance of the c-advance mechanism. You should have full advance by 15~1700 RPM's so you may not be getting all of the adv at your RPM's if the weights are sticking. Try rotating the dist at full cruise or at a point that the c-adv is fully advanced.

The prop and hull play a big part too as far as Vac performance is concerned. My ole #35MkII with the Indigo prop would cruise at 2100 RPM's at between 6~7 inches of vac and max out at around 2600 RPM. My engine was old tired and low compression numbers however it was well tuned and the carb had been balanced by me.

Try the dist tweek and then record the numbers. A higher vac number at a "given" RPM means a gain in performance.

Most important is gathering the numbers when the tune is fresh and the prop and bottom are clean. Any changes can be easily identified as Joe pointed out.

Dave Neptune
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