I have a 1989 175 Merc, #C127467, which had previously been missing its top end. It wouldn't go above 4000 rpm except for 3 to 4 second random intervals. After searching the archives (a great source of info) I began with the easiest and decarbed with Valvtech, installed new t-stats, new plugs (BU8H) and new water pump. When replacing the plugs, 1 year old, I found they were fouled, which appears to be somewhat normal, however the starboard side plugs, 2-4-6 I think, were more fouled than the others. Compression is good, 119-121. The boat now runs normal. A couple of questions:<br />1. Could I be masking any deeper problems with the decarb, considering the poor performance prior to tune up and certain plugs fouled more than others. (probably a long shot but was curious)<br /><br />When trolling, it runs rough and every so often will stall. This has has happened before and I understand that this is an occasional thing for this motor, but one poster recommended using hotter plugs, possibly BU10H and higher octane gas. I am a little uncomfortable using different plugs, but was curious of other opinions. I also was trying to adjust the oil pump by aligning the marks, but there are 3 different marks on the oil injection arm and was wondering which to use.<br /><br />Again, many of these symptoms appear to be normal for this motor, but was wondering if there was anything I could do to improve overall performance.<br />I am sorry for the lengthy post, but thank you in advance for any suggestions.
