hi all my mariner 50hp 1991 will only rev a little faster than tickover, push the throttle forward and it just stays on the same revs but sounds as if its going to cut out, even on tickover it is very jumpy and not at all smooth, don't know if it is a lack of fuel getting through or a problem with the plugs, points etc. where should I start and how do I find a manual on how to do this, I can do all this on a car no problem but don't know where everything is on an outboard. cheers.