Hi Recently my 1987 115hp Yamaha has developed a slight miss at idle. I noticed that at full throttle it revs out to about 4950 rpm where as it use to rev out to about 5100 rpm. Is something bad developing here - spark plugs were changed about 10hours running ago / 6 months. Where should I look for the problem or am I getting flustered about nothing. It sounds fine when running above idle - no miss that I can tell. Any comments would be appreciated thanks in advance.