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Mr. Demeanor
09-29-2008, 01:12 AM
I recently replaced a compressor. Prior to the comprssor failing, I had experienced a high idle in neutral a couple times. The engine would idle at 1000rpm until I shut it off and restarted it. When the compressor let loose, I kind of figured it was related to that as I ended up with a few bad air injectors. I have now replaced the compressor and it did it once again. It is very intermittant. I first thought maybe it was a TPS adjustment but that wouldnt explain why it goes away if I shut the engine off and restart it without doing anything else. Suggestions for troubleshooting appreciated. I do not have DDT and would like to do some troubleshooting on my own first if possible.
I will be checking the TPS per the shop manual instructions when I get a chance but thought I would ask here is this is anoter one of those known issues.

pier pressure
10-01-2008, 08:57 PM
mr demeanor, please advise back when you find an answer to you problem. i have a 07 300xs opti that is doing the same thing, and i also had to replace multiple air injectors on the right side.. thanks in advance.

Mr. Demeanor
10-02-2008, 10:08 PM
Hmmm...I will let you know. I havnt had a chance to look at it yet. This started just before the compressor went out so I really thought it was related but everything is new or tested by brucato.

Mr. Demeanor
10-03-2008, 09:06 PM
I did some work on her today and hope I have fixed the issue. WIth engine runnig, the slightest touch of the lever on the TPS sent the idle up to 1000rpm. I took all the linkage apart, cleaned, and reassembled. The roller that follows the aluminum ramp was all gungy. I cleaned all that off and cleaned the crud accumulated on the ramp itself. This seems to have allowed the TPS to disengage a little further in neutral. I also noticed that at wide open, the butterfly and TPs were not quite all the way open. A quick adjustment of the stop screw for wide open throttle (1/2 turn did the trick) and I took up that play.
This problam is so intermittant that I wont know until I run the boat awhile. The TPS assembly (where it rotates) was a little dirty as was the rest of the linkage. I really think the tps was just hanging up a bit and hopefully I fixed that.

Mr. Demeanor
10-05-2008, 12:34 AM
Put an hour run time on it tonight and no high idle issue. Thats not definitive but a good start. It also seems more responsive.

Kings Marine nz
10-06-2008, 01:57 AM
Your engine is a 3ltr opti ?? Have you had the updated throttle linkage put on the TPS ? - there is a slight geometry issue with the throttle linkage from throttle arm to TPS which makes it super sensative to lever movement. Mercury made a special TPS arm that cures this issue and made PCM program changes to also help with this issue. :cheers:

Mr. Demeanor
10-06-2008, 11:19 AM
Your engine is a 3ltr opti ?? Have you had the updated throttle linkage put on the TPS ? - there is a slight geometry issue with the throttle linkage from throttle arm to TPS which makes it super sensative to lever movement. Mercury made a special TPS arm that cures this issue and made PCM program changes to also help with this issue. :cheers:


I have no idea and did not know about this. Mine is a 2003 225 Opti and I had thought the 03's had all the updates??????

My engine was built in 2002 however.

Mr. Demeanor
10-06-2008, 12:09 PM
Just got off the phone with Merc and they were no help. They could not find any record of a service bulletin however, I had them look up the individual TPS linkage parts and there is an updated part number for the TPS link arm (old 883082 new 8M000811). I am going to go talk to my dealer but I know them and they will want to hook me up and charge me diagnostic blah blah blah $$$$$$$$
If you happen to have the service bulletin number, I would appreciate it. I have no way to know about the PCU upgrade though.
Thanks for your help.

Kings Marine nz
10-13-2008, 04:32 AM
Have looked for but can not find original bulletin. The updated plastic arm on TPS is curved (orig was straight) and throttle arm was longer. PCM change could have been updated by dealer without replacing PCM part number but should be 859610T71 or T73 (225HP) depending on boat size.
Trying to find issue without DDT or laptop makes it pretty hard. Generally those engines had a high TPS voltage at idle compared to allowable range
std is .04-1.3 volt at idle , some engines had up to 1.8 volts and 3-4 % Throttle open reading at idle which is why they could have high/sensitive idle speeds. A reading of about .7 volt was about where you would want it.

Part of the PCM change was the way the PCM read the TPS idle volts, previous it read the idle volts at key on and then assumed that this voltage would always be the idle volts for rest of time engine was running (so if at some stage the throttle is returned to idle and TPS volts are off by .5 volt, idle would remain high) , then when engine switched off and back on the PCM took another reading of idle volts from TPS (i.e. engine would then return to normal idle). The change allowed the PCM to ignore if TPS volts where high (or low) when key was switched on but when below a predetermind level it knew was the idle range - also engine had raised idle speed from 550RPM to 575RPM - this was changed for other reasons but helps to identify if it is the newer PCM:D

Mr. Demeanor
10-13-2008, 09:45 PM
So far the issue has resolved since cleaning the linkage, roller, ramp, and TPS assembly. I will compare mine to a friends with a 2004 225 and see if there is a vivsble difference in the TPS arm.
Thanks.

Mr. Demeanor
10-30-2008, 01:19 AM
The issue appears to have been resolved by cleaning and lubing the TPS and linkage. I particularly think the gunk built up in the ramp and roller was the issue.

Mr. Demeanor
04-17-2009, 12:25 AM
6 months later and still good.