Troubleshooting Mercury Optimax 115 Problems to Know: The Mercury Optimax 115 is a direct fuel injection (DFI) outboard in the 115 hp range. It is a beast in the 115-hp range with a two-stroke engine. However, even this beast faces problems after being used for an extensive period of time.. I have a 19 ft Trophy that has a 115 HP Mercury Optimax outboard that has been working like a charm. It is set up with a SmartCraft gauge and the problem is that it sends an alarm anytime I go over 4,000 RPMs. The loud beep is joined with a picture of an engine and bell on the screen. As soon as I throttle back the alarm goes away.
Re: 115 Mercury Optimax problem If you were getting your reading from the vapor seperator you were reading the low pressure (boost) pump, which is correct for that pressure. You should post your serial number because your air pressure might need to be 95 +/- 1 psi and your fuel pressure should be around 110psi.. Mercury Optimax 115hp Major Problems. Jump to Latest 30K views 12 replies 12 participants last post by tubejig Apr 25, 2010. B-Bay Walleye King Discussion starter. 732 posts · Joined 2007 Add to quote; Only show this user #1 · Apr 24, 2010. If anyone knows of anyone else that has had these troubles, please let me know, I'm desperate..