I recently purchased a 1987 28? express with twin Volvo 260hp IB. She ran great for about ~30 hours of use with out a problem and then the Starboard engine started to give me some trouble. I found the carb primaries flooding and rather than rebuild the rochester, ordered new edelbrock 600 and quad adapter plates to replace both carbs. In the mean time, I also decide to replace /convert both engines to electronic ignition too (coil, electronic module, cap, rotor and wires). When everything was done I took her for a ride. After running it up I heard a pop (exhaust back fire) on the starboard engine again? So I checked timing and found it way advanced 30deg btdc at idle (should be 8deg). This seemed very odd as I did not pull the distributor but reset timing to 8deg, verified it was advancing (~17 deg at 2K) and tried again. This time it ran up nice but after about 5 minutes at cruise (2800 rpm), it started to break up and then popped back through the exhaust once again. I backed it down and decided to go back on one engine as it would barley run at that point. At the dock, I double checked the firing order, checked compression (even 155-160) replaced new plugs, and ran it with valve covers off to verify push rods rockers and oil flow which all looked Okay. Stumped ? I pulled the cap to check it and found that the brand new rotor was burned on the front right corner. Hmmm, was this from running it so far advanced? I put the old rotor back on that I kept as a spare and started her up. Idle was normal so I took her for a ride only to have it pop back again after cruising for a few minutes. Checked the rotor and cap again and they look fine. While the compression looked good, I was thinking that maybe a valve is hanging up when it gets hot, so I changed the oil and added a qt of mystery oil. I would very much appreciate any input on what to do next.
