2003 200 hp Opti loses 500 RPM when trimming, won't go above 3000 RPM now

[Nova Kaw 650]

The only other thing I can add is possibly a bad trim motor.

[Savage]

Thanks Don and Scott and everyone. I'll be sure to take a look at all you've said, check the battery, and all the connections. WRT the Smartcraft Tach I have, it's a Smart Tow type, designed to monitor more than one engine, I believe, if you need to (I don't . . . only have the one Opti 200). It's also designed to allow one to control the boat from the gauge at tow speeds, but this is an option I don't believe I'll ever use, either. Don, in looking thru the manual, I didn't see a "Tanks Not Installed" option in the calibration section, but I'll look again. Let me know if you have anymore detail on this. Scott, I'll definitely check all the connections. FYI, the SC voltage reading at mid RPM says about 13.7, which sounds like the alternator should be charging ok. But I haven't yet measured the volts at the alternator with a DMM. Need to do this. And check over all the cables. Here's a thought: when I took out the old analog trim gauge in favor of the new "daisy chain" digital gauge from SC, is it possible that one of the old analog wires (which I tried to cover loose ends with electrical tape) might be shorting out on something causing the drop in RPMs? FYI, I also put in digital "daisy chain" oil temp, water temp, and water temp gauges, as well. Perhaps an old analog wire (now un-used) from the old gauges is somehown loose and causing the short? I tried to tape off all the old wires when I hooked up the daisy chain of SC gauges. Just thinking out loud. Please comment back. Thanks for all the help! I really appreciate it! Mike

This scenario is not likely to happen, only when you hit the trim motor.
A "Short" will trip a breaker or blow a fuse, likely stopping some other device in the boat from functioning.

[Ogreman51]

Ok, thanks everyone. I need to take some time to go over everything. Boat is actually stored at the lake about 90 miles away, so I need to plan a day long trip with all these things in mind. Thank you for all the ideas.

[Ogreman51]

Ok, it's been awhile, but here's what we found out. My mechanic began to suspect fuel flow problems with the engine by the way it was acting. On my engine, Mercury puts both a low pressure fuel boost pump, and also a high pressure pump. It turns out that he had a used 225 Optimax that he has been using for parts, and the two pumps on it are identical to mine. When he swapped them out, VOILA!! Both the RPM and the trim problems were solved! Turns out that the two pumps on my engine were cheap, foreign made parts, and NOT genuine Mercury, and they were acting up! So, lesson learned. Use Merc genuine. I've already ordered replacements that are genuine Mercury. FYI, the high pressure pump is Mercury part # 888725T02 and the low pressure boost pump is 888733T02. It appears these two pumps are very common on many of the old EFI, DFI and Optimax engines. Mike

[Ogreman51]

New issue: Have any of you heard of the company named Walbro? Supposedly, they are one of the manufacturers of "genuine Mercury " parts? Like the fuel pumps on my 200 Optimax? I purchased a low pressure fuel boost pump along with a high pressure fuel pump that were Walbro (per mechanic's ok), and the engine won't run properly with them (coughs and sputters). But the motor runs fine with the pumps from my mechanics 225 Opti. What gives? Comments? Merc parts truly are different and are the only kind a person should use? Thanks. Mike

[Savage]

I think you answered your own question.....install the Mercury parts.