mercruiser mefi 3 discussion

[bud37]

Source of the post I don't understand why you need the shim. Is it not possible to adjust the adjustment screw without removing the throttle body??

You should not have to adjust the TPS, but might have to reset the TPS settings in the ECM and relearn the TPS range. Not sure how to do that though on these engines.

The shims provide an easy and accurate way of checking the throttle plate adjustment and not play with the oem setting.The screw head is under the body near the fuel rail , can't see it , don't know if it is torx or allen and my understanding is they have made it somewhat tamper proof.The paint in the other torx fasteners was bad enough ...
Ran the boat today and all was well, engines all good, no issues...... except it is raining and foggy again, so back home we went.....I will connect up to it next week and see if it has learnt anything.I hear ya about the tps, lets see where this goes...let me know if you find out how or if you need to reset the tps......

[Viper]

Unless you have a DTS application which I doubt applies here, there is no TPS setup.

[bud37]

Source of the post Unless you have a DTS application which I doubt applies here, there is no TPS setup.

What is this DTS you mentioned ? Haven't run across that term yet....

[Viper]

Digital throttle and shift - fly by wire, no cables.

[bud37]

Yesterday got in the boat, very nice day and quite warm under the shrink.We took the throttle bodies off both engines to bring home and examine a little closer, I will post some pics....they are very clean and both appear to have the same throttle stop screw settings.That is something I would love to see a spec for, my only understanding of that opening would be you set it on a running engine to get 40 or so IAC counts at idle.....but how did maker set it ?......the torx stop screws are stuck so I will leave some PF on them for a while and try again later.

Upon very close look I noticed something on the throttle stop arm....more on that later.

Also removed the ignition sensors in the distributors ......there was still rust stuck to them and some corrosion on the circuit boards ( original two wire )...will replace with the sierra sealed ones, new caps and rotors too.... as the burn pattern in the caps doesn't look right, which could possibly have been a result of there being two gaskets on the cap...

[bud37]

A small update......both throttle bodies showed maladjustment and the throttle blades were contacting the bores causing one to stick and bind ( closed at a different spot each time ).This I believe was a result of poor assembly of the blade positions and the cables being adjusted so they were slamming the blades shut.( wear evident on stop arm )
Cleaned up the damaged area on each , now no binding ( smooth) by raising the throttle stop .010". IAC counts already high so this might do the trick, I can always adjust further when get engines running. There will be a slight amount more air at idle now as measured in the bores.
It will be interesting to see where the TPS voltage at idle goes now. I have too much time on my hands heh.

[bud37]

Another small update....when checking the part #'s for the 90mm throttle body on the 6.2 377 cu inch, it appears that exactly the same one was used on the 350 cu inch....now if you do the air flow calc for 650 rpm idle the 377 uses about 5 cfm more air than the 350, which would account for the IAC on the 377 having more counts at idle, spec says 40 or so....cant be done.The next year after mine they changed the body and the ecm. Come on Mercury Marine please explain how this is supposed to work please.....no wonder there seems to have been idle issues and so many IAC replacements according to internet searches.
Both bodies on my engines were slightly different in setup. Now they are the same.

[Viper]

Did you check to see if both ECMs have the same version number or are different before you made the mod?

[bud37]

Same part #, same checksum.......the side with the more frequent issue was the one with the blade interference problem and the highest of the two IAC counts.There seems to be only two ways for air that can be calculated to get into the engine, throttle blade gap, and the IAC port which is the one trim point there.
I am disregarding any vacuum sources here as they are a non issue.

I will examine the adaptor plate further as to that hole I mentioned.

[bud37]

Upon reinstalling everything today x 2 (ignition sensor, cap and reluctor, and throttle bodies), the adaptor plate has no other port in it....all went together well....would be nice if all works as it should ( fingers crossed )....spent a fair bit of time rerouting plug wires away from potential problem spots........