Intermittent High Idle

[apdriver]

250 ProXS, Serial#- 1B962763. Serviced last May. 280 hrs Total time. Last two times out have experienced intermittent high idle. When I shut the motor down and restart, it will idle fine. To prevent further and future issues, I took it to a dealer with a merc master tech and he checked the air and fuel pressure and said there were no faults. He checked the throttle cable, linkage, hot foot. Ran fine for him so didn’t do anything. Can or should I keep running it? Not sure what direction to go with this one. Any help appreciated.

[Seguin Fisher]

I had that exact thing on an 02 optimax 200. About 1 in every 10-15 times I put it in idle, it’d rev like crazy. If I shut it off then turned it back on, it’d be fine. I never did get it solved, as I sold it a few months after it started doing that. Always wondered what the cause was.

[Jtreed99]

I had a similar issue and it was tpi

[Idaho Sandman]

I had a similar issue and it was tpi

Whats “tpi”? Assuming you mean TPS? Throttle Position Sensor?
sounds like the culprit as mine started this last fall right before I put her away for the winter. Talked to a local mechanic who agreed that’s more than likely my issue as everything checked out when I had them service it mid summer. Sounds like an easy fix so I will probably replace it myself.

[Jtreed99]

I actually meant TPI throttle position indicator yes it’s the same thing as tps in the automotive world but the Mercury bag you get in the mail or from your dealer will say TPI throttle position indicator on it. Plug and play and two bolts easy fix.

[apdriver]

Is there any way to test the TPS to see if it’s operating correctly?

[angle iron]

Is there any way to test the TPS to see if it’s operating correctly?

Scan tool

[apdriver]

Scan tool

Just looking at the service manual, it says that the TPS position can be monitored with the CDS. Gives voltage specs at idle and wot. By scan tool, I’m thinking you mean CDS. I don’t have one of those.

[Savage]

Just looking at the service manual, it says that the TPS position can be monitored with the CDS. Gives voltage specs at idle and wot. By scan tool, I’m thinking you mean CDS. I don’t have one of those.

Yes that what he is saying.

[EuropeanAM]

Either the throttle linkage is not consistently coming back FIRMLY against the idle stop (ie: debris in hotfoot, lack of lubrication to hotfoot moving components and cable end, insufficient spring tension, worn or improperly adjusted cable, etc), OR the TPS has a "glitch" near or at idle.

[apdriver]

Thanks for the replies. I’m going to just double check the hotfoot, throttle stop, linkage,and lubricate. Water test it one more time and if it’s still acting up order a TPS from Rhonda. Thanks again, fellas.

[Mon Mariner]

I had a 2000 Opti 200 that would rev by itself. Only happened 3 times before I got it to a dealer. After checking and rechecking with Mercury the dealer took the air pump apart and found (I watched it happen) a small piece of maybe gasket material or plastic in the cylinder. It ran perfect after that.

[apdriver]

I replaced the TPS and the three bolts holding it in place seemed like they had a bit of loctite on them. Wee bit hard to remove and I could see something on the ends. May have been just a little corrosion, not sure. Manual doesn’t say to use thread locker on those just to torque to 23 in/lbs. Do they require removable thread locker?

[EuropeanAM]

Red liquid loctite.

[apdriver]

Thanks Don.

[apdriver]

As a follow-up, after replacing the TPS, have been out multiple times fishing and the intermittent high idle problems are solved. Thank you guys for your expert advice once again. It’s much appreciated the time taken to support these engine owners in their efforts to keep their motors in tip top shape.

[EuropeanAM]