Second new Merc motor issues...

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mchad

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Long story.

Two years ago my 2000 Merc 5.7 blew up. Over the winter of '12/13 I bought and had installed by my marina (a Merc dealer) a new (Mercury Reman) 383 magnum MPI. Wonderful motor - about 100hp more then the tired 5.7 carb I had - the joy of fuel injection start right ups, etc. Until about 50 hours when it developed a knock. After about a month of trying to figure out if the knock was coming from the sterndrive, the transom, etc, we finally tracked it down to the motor. (I had a post here about it) Merc sent out a field engineer who went for a ride with me, and said, "Yep, its got a noise" - he suggested that it may "go away" as it breaks in more, and that I use it the rest of the season and see what happens. He also said they would replace the motor for me, if that's what I wanted.

So end of season comes and the noise is still there. Being the skeptic that I am, and NEVER having had a brand new motor make a noise like that, I opted for the replacement.

Fast forward to this April. New motor installed over the winter (no charge to me) - I come to the marina the day its dropped in to move it over to my slip. Go to start, it turns over but no start. 10 seconds of starter, no start. Having had MPI motors before, I know its a turn the key and it starts right up situation. However to get it started I basically have to give it about 1/3 throttle to get it to catch. I let the marina know. This now goes on for about a month, replacing the harness connector from my boat to the motor, replacing the ICV, nothing. All along I'm suggesting its a ECM (or PCM as Merc calls it) which they finally do. They tell me that the old PCM is marked "Freshwater cooled" which mine is not, but that shouldn't matter I don't think. Anyway, with the new PCM it starts fine. I didn't open it up during the first 10 hours for break in, but once the new PCM was in, and I was at about 13 hours on it, I opened it up one time to test it out. Would not reach WOT RPM's. Only would get to about 45-4600 rpms. Took about 10 seconds to get on plane. This is a 24' Crownline 242 BTW - the previous knocking motor would hop up on plane in about 5 seconds and WOT at 5000 RPM - right where it should be according to spec, which is 48-5200. Motor is definitely making less power then the previous. Note: Same weight on the boat, in fact the fuel tank was only at 1/4 when I tried the WOT. No additional people, or load. I think the exhaust smells a little rich when idling, but that could be my imagination.

So I asked the marina to reach out to Merc and see what they can do.

Which I suspect is going to be nothing, since the motor does run ok, just underpowered. Too bad there's no Dyno for boats...

Any suggestions on how to address this with Merc?

Thanks, and sorry for the long winded story.

Edit: Just to mention, I had been through a couple half tanks of gas during the first 13 hours - all that rpm varying during the break in plays havoc on gas consumption, so it's fresh gas...
 
<"...They tell me that the old PCM is marked "Freshwater cooled" which mine is not, but that shouldn't matter I don't think. Anyway, with the new PCM it starts fine....">

Maybe it does matter. I know the engines run at different temps. I leave everything beyond that to smarter folks than me.

As to what they are going to do.... That is up to you. You can only play softball for so long and a new engine that doesn't come up to spec demands Merc do something.

FWIW, any engine can be Dyno'd.

Good Luck.
 
I'd have the timing checked and see if its in spec. That motor should rev to spec if tuned properly.
 
quote:
Originally posted by SCORPIO

I'd have the timing checked and see if its in spec. That motor should rev to spec if tuned properly.

Click to expand...


Thanks, but aren't MPI PCM controlled motors fully electronic ignitions with no timing adjustments? Besides, it's under warrantee and the dealer is doing everything.
 
Could be, I'm not familiar with the MPI set up. The dealer should get it sorted out or get you a new motor. Merc should send a field service rep out to see that engine and get it running properly. Keep the pressure on them and you will get action.
Best of luck.
Let us know how this works out.
 
quote:
Originally posted by mchad

quote:
Originally posted by SCORPIO

I'd have the timing checked and see if its in spec. That motor should rev to spec if tuned properly.

Click to expand...


Thanks, but aren't MPI PCM controlled motors fully electronic ignitions with no timing adjustments? Besides, it's under warrantee and the dealer is doing everything.

Click to expand...


No, there is a base timing which should be verified. Have you run the boat with a laptop with Rinda software attached to the PCM? Also have you performed a full condition check in accordance with the Mercruiser manual?
 
The dealer should have everything set up and ready to go.

Call merc again and tell them the motor won't work. The very least they should do is send out a tech. Maybe you'll get the correct engine for your ECM...or visa-versa.
 
quote:
Originally posted by GeeBee

quote:
Originally posted by mchad

quote:
Originally posted by SCORPIO

I'd have the timing checked and see if its in spec. That motor should rev to spec if tuned properly.

Click to expand...


Thanks, but aren't MPI PCM controlled motors fully electronic ignitions with no timing adjustments? Besides, it's under warrantee and the dealer is doing everything.

Click to expand...


No, there is a base timing which should be verified. Have you run the boat with a laptop with Rinda software attached to the PCM? Also have you performed a full condition check in accordance with the Mercruiser manual?

Click to expand...


Not my place to troubleshoot. It's a new crate motor under warrantee. They need to get it sorted. I just filled the tank (70gals) on Friday and with me and my gf on board it would not plane w/o full tabs. As I said earlier, even my orig 5.7 2bbl had more power. Something is wrong. Dealer/marina was loaded up prior to July 4th weekend, so they haven't done much yet. They were told by merc to do a compression and leak down test on it. So we'll see what that brings.

I notice a strong gas smell when running. Almost like a cylinder isn't firing... I'm relaying all that to the marina of course.
 
http://www.2carpros.com/forum/automotive_pictures/188069_98k1500fireorder_1.jpg If this has the flat crab type dist cap the firing order is not what you think
 
quote:
Originally posted by GeeBee

quote:
Originally posted by mchad

quote:
Originally posted by SCORPIO

I'd have the timing checked and see if its in spec. That motor should rev to spec if tuned properly.

Click to expand...


Thanks, but aren't MPI PCM controlled motors fully electronic ignitions with no timing adjustments? Besides, it's under warrantee and the dealer is doing everything.

Click to expand...


No, there is a base timing which should be verified. Have you run the boat with a laptop with Rinda software attached to the PCM? Also have you performed a full condition check in accordance with the Mercruiser manual?

Click to expand...


That might be the case with the Mercs, but my Crusader 5.7L MPI's at least have their base and advance timing completely controlled by the ECM. Turning the distributor only affects Cam Retard, not timing at all.

A couple more thoughts: When I switched to 5.7 MPI's from 5.7 carbed , Crusader required an increase in ID of all accessory exhaust parts: hoses, mufflers and transom outlets to handle the higher exhaust flow and the new higher spec'd WOT rpm to avoid back-pressure.
- Did you do that when switching to the 383 MPI?

How old is the gas? Stabilized when new?
If the gas has deteriorated with reduced octane rating now, the engine could be sensing knock and retarding timing which would certainly limit WOT RPM.

I'd also mention even though my old carbed engines were properly propped to attain towards the high end of the spec WOT RPM range with full load onboard, when I had the new potentially higher-revving MPI's installed I found I could still only attain the same WOT RPM as the old pre-vortec engines even though each of the new engines provided 60 add'l hp. I ended up having to drop pitch from 19" to 17" ( all else remaining the same) to attain the new 5000 rpm recommended WOT.

That was disturbing but the result was just fine. I ended up with higher WOT STW, higher NMPG at the same old cruise speed and higher STW cruise speed and RPM with same NMPG as I used ot have at the old slower cruise speed.

Plus the 27' I/B boatw/ marlin tower easily gets on full plane in about 3 seconds using no more than 1/2-2/3 throttle, and maintains speed a bit better in heavy seas. .

And I would second "Alien"'s advice to check the proper spark plug cable connections at both ends ...if... your engine has those crossover flat distributor caps with the numbers molded in . As Alien points out, cap post order is NOT the same as firing order due to the internal crossovers. .
 
As Sandy says, a prop has an absolute maximum speed it can obtain. It's confined by it's pitch. Load and slip can reduce it's maximum attainable speed but it will never be able to go over it's mathematical maximum other than increasing RPM.
 
Thanks for the good suggestions. I would suspect much more of what you said (exhaust, etc) if I didn't have the identical motor last year which ran perfect (except for the knock that ended up causing the replacement) - same through stern drive exhaust, same prop (bought new with the new motor April 2014), same load.

I've been through two fills of gas, and what was in there from last year was stabilized properly.

I don't want to mess with it as its a warrantee issue at this point and I don't want anything I do to jeopardize that.

It's just incredibly frustrating spending 10k for a motor and having TWO bad...
 
I had a similiar thing 2 years ago. Ended up being a
defective brand new spark plug.
 
Haaa! Reminded me, I had two new plugs in a row go out on my harley. Sounded like it was about to explode.
 
Update: I'm not going to get anywhere I'm afraid. Marina under Merc's instruction, did a compression and leak down test, which came back normal. They said they took it out for a ride and said it hopped up on plane right away, but still only made 4600 rpms. Then they started with "maybe you have more weight on the boat" bs. When I asked what they thought about the gas smell, he said, yeah, I smelled it, have no idea. I also suggested since they were pulling the plugs to do the tests, they replace the plugs just to be sure. Forgot to ask if they did. He said, well, we'll tell merc what we found and see what they say next.

I here is a video of not being able to get up on plane:
https://m.youtube.com/watch?v=10ApuoLA_yE

Just FYI, this is a 24' crownline 242cr. I NEVER had to use tabs to plane, even with the original 5.7 2bbl motor. Last years 383mag mpi hopped up on plane so fast it was barely 5 seconds...me this one just wallows along until I give full down tabs...

They said it hopped up on plane no prob. I know the tech working on it is a smaller guy, but it's a 350hp motor- adding let's say even 225 more pounds for me (I'm a big guy) and my gf and a full cooler and fridge, shouldn't keep it from planing. And again, last year I hopped up on plane with 4 big guys onboard no problem.

I'm getting fed up. Seriously.
 
Maybe do the same video but try to record the engine noise more. Also video the engine set up itself.
There are some pretty sharp guys in this group. They may pick up on something.
Just a thought.
 
Yup, Underpowered. It's acting like it's just not advancing. Can you put a timing light on while accelerating?

Another possibility is the timing chain was set up a tooth off.

I don't know enuff about fuel injection but it could also be running too lean. Doesn't take much, but can you partially close choke slightly while accelerating? Be careful, if that's your problem, it'll really jump up on you.
 
quote:
Originally posted by jtybt15

Yup, Underpowered. It's acting like it's just not advancing. Can you put a timing light on while accelerating?

Another possibility is the timing chain was set up a tooth off.

I don't know enuff about fuel injection but it could also be running too lean. Doesn't take much, but can you partially close choke slightly while accelerating? Be careful, if that's your problem, it'll really jump up on you.

Click to expand...


I don't think MPI motors have chokes, Charlie. Mixture is all controlled by the computer (keep injector open longer,etc.) Which makes diagnosis such a remarkable pain in the ass. I can do the timing check though.
 
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