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 ?

I had 560 on them but had them tested and everything was perfect, did the refresh on the head just to be safe.. had a DDT test when bought the boat 8 years back and they were baby’d. I bought the boat with 212 hrs in them, change the oils every 20 hrs etc.

So if the refresh is the cause, should I just reprogram my Pcms to 5400 to get rid of the warning? I don’t know that 525’s should be running over 5200 course I could alway just throttle back.

I just get nervous when something like this changes and the mechanic says he has no idea why. And the last think I want to do is blow my engines because they may have been reinstalled incorrectly, that would suck.

Thanks again for your input Brother…..greatly appreciated 😎

1. pull back the sticks
2. reprop as Sutphen 30 said
3. remap the PCM's I wouldn't they are set there for a reason, and it will probably cost more than prop's

What was the gps speed before and after?

Are you running the same mph as before or is it faster now? Sounds like the engines might have been tired.

Couldn’t agree more lol thank you 🙏

Hey bud, I can’t answer that because I haven’t tested the boat myself, it was taken out for adjustments by the mechanic. It was just what he told me and before I take it out, I wanted to run my problem thought offshore before taking it out this coming Tuesday.

I might change the props if I can gain some top end out of it so long As I don’t need a football field length to get planning LOL

Why not just send your props out and have them cupped a couple degrees rather than the expense of new props. Just a suggestion! I’d take the extra 200 rpm’s and be great full. Go buy your mechanic a case of beer 🍺

IMO YOU need to take the boat for a ride. Maybe the mechanic had it over trimmed?

I wouldn't buy or modify anything till it was confirmed.

Maybe you’ve shed a bit of weight by replacing the original water logged and heavy wood stringers and transom. That in conjunction with the engines being refreshed may have bought you the extra 200 RPMs. Like others have said, get it out there yourself. Trim it to how you usually do. Note the speed outputs at the higher RPMs and compare to what you previously would achieve.

as said above you need to run it. right now we still dont know if the transom itself was replaced in which case they may have raised the gimbal height a little and now we find out you have not run it only the mechanic which means he may be trimming different than you do, etc etc. lot of factors in here that can account for 200 rpms.

Ok, all good points but I’ve trimmed this puppy out to the max at full throttle with all kinds of variables iE. Different fuel levels, passengers, weather conditions etc and could never get past 5200. The entire transom assembly including the gimbals were change as well, I had the stern wall rebuilt with fiber board. But they never removed the outer fiberglass, just everything from the fiberglass skin inwards then in place of using wood and fiberglass, they used fiber board so I never have to worry about rot or humidity again. The thing is, the original holes were used to install all the new parts so it’s near impossible for them to have either raised or lowered the position of my drives however,
to your point, it probably wouldn’t take much to create a 200 RPM discrepancy 🙄

I’ll run the boat Tuesday and pop back in with an update. Thank you again, I hope you have an awesome day brother….😎

Check the toe of the drives, I.e. pointing in or out from each other. If the tie bar adjustment is way off it could effect slip %

He was asking if the transom of the bost was changed. Not outdrive transom assemblies.

My wuestion - did mph go up with the rpm’s ? Stay same ? Go down ?

They looked perfect because I am completely anal however I will measure them to make sure the mechanic did not screw that up, I didn’t realize that could cause slip but that makes total sense thank you

yes sir the transom was changed however the outer fiberglass 1/4 in wall was left in intact.
they just added the fiberboard on the inside then cud the holes through the fiberboard using the exterior shell if you wish as a template so the holes remain in the same place.

As for the speed going up with the RPM’s I have no clue, he said he backed off when he heard the warning horn go off.

I’ll see Tuesday when I open it up, I usually get 86, 87 mph fully trimmed at 5200 so I’ll see On Tuesday and get back to you guys for sure with an update

Thanks again guys I really appreciate your help

so are you going faster?
I see above you answered it.

Your mechanic prob trimmed the drives higher than you do or ran it different than you do

good morning, I guess we’ll find out on Tuesday LOL. On another note, do you have any idea what the cost is for rods, rockers and springs only per head? I just want to make sure I didn’t pay for the parts. Thanks in advance and have an awesome day

You had all that work done and gained 200 RPM? Sounds like a win to me. Just about every story that begins with I had major mods/rebuilds ends with, "I lost performance" or "something isn't right".

Let us know how it goes after you run it yourself and the worse that could happen is you get new props and go even faster.

You need to put " push " in front of this in your case, when you say rod's us gear heads think connecting rods which can be 10-15 times the price of push rods, without the brand name of the components replaced it would just be a guess on our part about cost, and I hope they did a valve job at the same time.

lol I get it but I did mention it was for heads and although I’m not gear head, I don’t thing push rods are in the heads bahahah…

kidding aside, no I did not do a valance job cuz nex year I’m considering putting 560 or 565 twins in it in place of 525,s. Research showed that at the very least, springs, pushrods and rockers would suffice. I’m just curious what the cost should be compared to what I paid for the parts assuming there upper middle to high end quality parts 😎

1. OE style rocker arms 250-400 per engine
2. push rods 150-200 per engine
3. valve springs 200-400 per engine

#4 which you should of done IMO is lifters 400-600 per engine

BTW push rods are in the heads. there the long round skinny things that make the valves go up and down......:sport009:

Wait a min, you have 560 hours on these engines and had pushrods, rocker arms and valve springs replaced? No lifters, no valve job, no head gaskets?
And you’re planning to repower next season? You wasted your money this year.

Getting rid of waterlogged wood drops a lot of weight off the boat. That alone could give you the rpm gain. Also putting in new valve springs can increase performance if the old were truly fatigued and allowing valve float.
As long as the compression is good on all cylinders I don't see why one would think he wasted his money. Those short blocks should be good for double what he has on them. Especially with 20hr oil & filter changes. And it certainly doesn't sound like he abuses them.

yes sorry lifters we’re changed and gaskets. And yes I’d like to repower next year but figured in case I have to push the expense off another season, I wanted to be sure I was not going to grenade my engines. If I can afford to drop 560’s in, I’d just sell my 525’s cuz there in perfect shape and pasted all the tests with flying colors 😎

another 300 bucks for a valve job while the heads were off would of been money well spent,

All good points and yes I rarely beat the boat and the compression is bang on where it needs to be. The DDT test when I pitched the boat 9 years back showed that the majority of the 212 hrs on the boat were idle, cruising and only 8 hours at 5200 so the engines were truly babied when I got it and rarely beaten since I’ve owned it. Don’t get me wrong, I drive it hard but it’s well maintained 😎

good luck on the test run tomorrow

500 and 525 lifters fail on the regular around 300 hours. Skipping the valve job isn’t that big of a deal, if he skipped on the lifters it would be just as close to having a failure as when he started spending all that money. But since they were replaced I retract my wasted money comment and agree, a little maintenance now, and sell them still running next year. I hope to do the same with my 525’s

Might not splash it tomorrow, I had a small crack on one if the headers that created a small leak and a replacement was ordered from the US. And apparently being overnighted to Montreal. If it lands here tomorrow, then No problem since he left the damaged one off making it a quick repair……just more frikkin money…..and time 🙄

i’ll keep ya’ll posted 😁

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After