Mercruiser 7.4L MPI slowing down
#31
Registered
They remind me more and more of part changers. If they have a scanner, it can be connected and the TPS can be watched to see if it changes when things happen, same goes for the MAP and most other sensors. The TPS, ECM (MEFI-3) and no longer available from Merc but may find new old stock. The MEFI can be reflashed if need be but so far there just changing parts. The $1400 for a TPS is mind blowing, but maybe they were talking about the ECM.
If it is the ECM (no testing has found it is) I would send it out for repairs before replacement.
If it is the ECM (no testing has found it is) I would send it out for repairs before replacement.
#32
Platinum Member
Platinum Member
I met with the mechanics today and spoke to them for a while. First of all they told me the first things that they did was clean the fuel pickup and anti siphon valve (they did clear some gonk out of it) but it didn’t fix issue.
They did hook up a fuel pressure gauge and do a measurement when the issue manifested and found there was no fuel pressure change. They also said the computer recording did not throw any code and everything looked normal thats why they were having difficulty identifying. They said when they’re running it at 4000 RPM the issue did not occur (it’s only occurring at about 3000 to 3500 RPM which is the sweet spot for the boat). They did suggest (before I did) hooking up a fuel tank and they also have what they call a boat-in-a-box which lets them hookup to the boats wiring to see if there’s an electrical issue. They also mentioned the possibility of a TPS (throttle position sensor) issue, but that costs $1,400 to replace so they are going to test with portable tank and boat-in-a-box first.
I assume replacing the ECM would be costly too (if the part is even available). One thing I never thought to try was to turn engine off for a minute when it does occur. If it is related to the computer but its fixing itself every time I take the boat out perhaps powering it down and letting electricity dissipate out of it would help.
Thank you,
Scott
#34
TPS is $85 part https://www.mercruiserparts.com/8m00...ensor-throttle
They said it’s no longer available from Mercury, but that I may find it used or after market and they told me when Mercury did have it available they charged $1,400 for it. For that reason they suggested that we try hooking up fuel tank and boat-in-a-box first.
#35
TPS is $85 part https://www.mercruiserparts.com/8m00...ensor-throttle
What would be the worst case scenario that would guarantee a fix? 2 weeks+ already in the middle of summer I’m trying to get this resolved ASAP.
#36
Registered
What would be the worst case scenario that would guarantee a fix? 2 weeks+ already in the middle of summer I’m trying to get this resolved ASAP.
As an example: gal has had problems with her VP diesels and many techs tried but failed to fix. A high priced VP fixer came in and fix the issues in a couple hours (Formula forum). The issue is where is the Master Tech
Last edited by AllDodge; 07-29-2019 at 06:30 PM.
#37
Charter Member # 55
Charter Member
To clarify I found the TPS on Amazon for $45 and they told me that’s not the part and that for mine it is part of the throttle assembly unfortunately. Its part 802622a1
They said it’s no longer available from Mercury, but that I may find it used or after market and they told me when Mercury did have it available they charged $1,400 for it. For that reason they suggested that we try hooking up fuel tank and boat-in-a-box first.
I'd find a new marine tech. The part # they gave you is for the entire throttle body.
The TPS is clearly listed as a separate part https://www.mercruiserparts.com/bam/...31918/2705/100
#38
Registered
Is Ac Delco #213-912 (GM#17123852) the same TPS ? Sure looks like it. About $25.00.
#39
Registered
I had a '99 Crownline with a 7.4L MPI that did something similar (not exactly, but close to your symptoms) and it ended up being the ECM. Merc replaced it at no cost even though it was out of warranty (replaced in 2003).
#40
Registered
Have you ran boat with hatch open when this problem occurs? Sometimes a minor exhaust leak can add enough carbon dioxide to engine compartment to alter performance , but not shut down engine. Not always visible. Good luck.