I do not no the first thing about motors!My Buddys boat has an older Ford motor in it.He had same issue with it loading up with gas etc. Had it worked on several times.Boat ran great when running from here to there.As soon as he tried to slow troll,is when it acted up.Couple-3 years ago he bought a smaller kicker motor for trolling.It has been the ticket!He recently purchased an extended handle(tiller?)Takes some time to get used to.But will be much more comfortable to work with on long hauls.NO mechanic here,maybe yours just needs an adjustment?Good luck with that,and the fishin!!!