Mercruiser 7.4L MPI Throttle Adjustment ???

[tpenfield]

Greetings,

I have a question about adjusting the throttle linkage on one of my Merc 7.4L MPI engines. The Port engine throttle linkage is currently out of adjustment and only reaches 84% of the throttle range on the TPS read-out (Rinda Diacom)



This with with the throttle lever at the helm full open - pressed hard against the instrument panel - so that is all the travel of the lever itself.

I assume I would need to adjust the linkage back at the engine to get the full travel at the TPS sensor.

*** My question is by doing so will it mess up the adjustment on the other end of the throttle range (i.e. the idle setting)? *** Is there a trick or procedure to adjusting the linkage for the MPI engines that I need to consider?

 

[Scott Danforth]

you may have slack on the port engine cable, with the engine off, have someone move the throttle while you check for movement in the cable just off idle

some controls have multiple anchor points for the cable, could it have been installed at the wrong point at the controls

 

[tpenfield]

you may have slack on the port engine cable, with the engine off, have someone move the throttle while you check for movement in the cable just off idle

some controls have multiple anchor points for the cable, could it have been installed at the wrong point at the controls

Thanks, - Yes I noticed a mention of 2 different attachment points in the Merc manual - One for the standard Quicksilver controls and one for the Merc Zero-effort controls. So, I'll check that out and compare to the Stbd engine.

I am also wondering if there is any adjustment up at the helm controls, or is it all at the throttle body?

 

[Fun Times]

Depends on the type of cable and shifter you have on your boat...Some may have adjustments at both ends but most standard Mercruiser cables and shifters only adjust at the engine side.

Also consider that (though the adjustment is very small/slight) the TPS sensor isn't seated/"Turned"/Installed just right to allow either idle voltage reading to be within a normal specification range or full throttle isn't getting closer to the higher 90's / 100 % range. A 100% reading is sometimes challenging to try and get to...90's seemed more common though.

First with engine off, key on, compare both engine readings and then still with engine off, key on, remove the cables at the engines and open both throttles by hand and see what the %'s says and go from there.

 

[tpenfield]

Thanks @Fun Times . . . I have the 'standard' (ie. bulky) Quicksilver controls. Your method of checking the TPS and linkages sounds like a good plan. The Stbd engine TPS goes to 99%, so I'd like to get the Port engine close to that.

 

[tpenfield]

Quick Update - Easy peasy . . . I was able to adjust at the engine end of the control cable. I got it to about 94%, which should be fine. There is a little bit of uneveness at the control levers themselves, causing the port lever to 'bottom out' before the starboard lever.

 

[achris]

My experience is that you don't want the sensor to be reading 100%. If you do, it means you're using the throttle body as the hard stop, and that'll be putting all the stress on the throttle body, and they don't like that.

Chris...

 

[tpenfield]

My experience is that you don't want the sensor to be reading 100%. If you do, it means you're using the throttle body as the hard stop, and that'll be putting all the stress on the throttle body, and they don't like that.

Chris...

Yes, I figure there is very little difference in the last few % of throttle position setting. I wanted to make sure the throttles reliably go back to the 0% position, so I could only adjust at the engine a certain amount.

At the helm control levers, the port lever - in the neutral position - is about 1/4" (6mm) more forward than the starboard lever. So the starboard lever actually has a bit more travel than the port lever. There may be some adjustment at the helm which would make them all the more even.