HELP !!! My Merc 525 EFIs are over revving !!!
 

Hi all, I had a ton of work done on my 2004 38 Fountain Lightening, too much to go into all the fearsome but here’s my problem. The mechanic that worked on my boat changed my springs, rockers and rods in both engines. I had the engines removed to redo all the stingers then bought new gimbals and the list goes on. So now the engines are reinstalled in the boat but it revs at 5400 RPM in place of the max 5200 RPM prior to the upgraded. I have the original document from when the boat was tested in 2004 from Fountain and it also states 5200 RPM max. Props were not changed so it’s not that.

Can anybody give me an idea as to why this would happen? Obviously my horns blowing like crazy warming me that I’ve exceeded the rev limit.

Any help or advice would be greatly appreciated.

Thanks in advance all

Barry

put a bigger prop on.

were the PCM's modified, rev limiter increased, why were the rods replaced

No I don’t believe they were modified. It was recommended to just change to pushrods, rockers and springs however the engines were removed, new stringers replaced with new gimbals installed then the engines had to be remounted on new stringers. Could it be something with the actual installation if the motors? Wrong angle perhaps or anything like that? Fuel pumps were changed as well to a more efficient style but no mods to the block at all. My mechanic has no clue why this is happening. How comforting

I could do that however, I’m more concerned with why there over revving at this point and want to make sure everything was reinstalled property. Once I resolve this issue, I can play with props. I’d have to ask 38 lightening fountain owners for the different configurations they’ve tried and the results they had.

have a great day all and thanks for chiming in 😎

you say new stringers and you bought new gimbals, so was the transom replaced as well? if so is the drive height the same as before? are these the same drives? hard to know as you did not state all the work done so there could be a piece missing that we dont know about.

Hi, yes complete transom assembly with gimbals were replaced with the same drives I had before. I can’t sander the question on drive height however if the same drives were installed, I assume the answer would be a yes lol. Sorry I’m not fully familiar with boat mechanics, but if a learning curve lol

I really appreciate your input though thank you

Im pretty sure stock those pcm's are set at 5400-5450 so I dont think you have an issue, did the engines ever cut out at 5200 before ?

hook a scan tool to them and verify the rpm's

I’m not sure what there set at but I can say that I have never been able to exceed 5200 and never had a problem running them for extended periods of time at 52 but now there revving 5400 and of course the warnings kicks in which is a pain in the ass but would prefer to fix the issue rather that just throttling back if ya know what I mean lol

Id say you were down on power and the refresh of the engines picked up 200 rev's, how many hours were on the engines before the refresh ?