www.iFourWinns.com

I just installed a new long block after burning a hole in the piston last year, I had just bought the boat and this was only second time using it, Volva Penta Ford 302 1995 2 Brl carb, The book says set timing at 10 deg BTDC, When I set it there it runs ok but if I turn the distributar past the 10 deg to between 10 and 14 BTDC the idle comes up and it sounds smoother and starts easier, did not know if it is safe to leave it there or do I have to leave it at 10 deg, Still not sure why I burned a hole in piston, I read it could be caused from timing and did not want to happen again, was running engine at full throttle to try and beat storm when it happened, read it could have been bad gas also

Advancing the timing will increase manifold vacuum = more airspeed through the carb.
Set the curb idle and idle mixtures with a vacuum gauge while sticking to the suggested timing setting.

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2011 Four Winns H180 SS.
Aussie built Mustang 2800.
SOLD - 1997 Four Winns Horizon RS

Does this boat have electronic ignition? If so you need to make sure you're doing it the right way so that there is no advsnce happening when you set the base timing. I have an old school engine with points type ignition. On this set up I check the points first then run it at the specified idle rpm and check the dwell. If it's ok then I set the timing at idle rpm.
The things that can cause burnt pistons and valves:
Over advanced timing
Fuel mixture too lean
Spark plug heat range too hot
Over heating
Over propping (prop pitch too high and engine never reached max rpm)

14* BTDC is way too much advance.
Fix your idle issue first.

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II