# 2020 Mercury seems to be over revving at 4600 rpm



## fishinfever (Feb 14, 2005)

Hey Sports Fans,
I have a 2020 75 HP Mercury 4 Stroke mounted on a 2020 Lund Alaskan 1800 Tiller. I have had the boat on the water 3 times with less than 2 hours running and when the alarm sounds and the rpms cut back I am not at WOT.
I made a video so that the dealer could see what is happening and installed a cheap Tach so I could try to figure out what is going on.






Everything seems to be fine until I go over 4500 rpm.
The book says Full Throttle rpm range 4500-5500.
The only thing that I think is out of the ordinary is that a large patch of paint on one of the prop blades just flaked off and the edges feel like it is all going to come off.

I know it is a stretch but what about a prop with one blade so different than the others or if that is an indication that there is something more defective with the prop.
I can't find information about when the rpm limiter kicks in and/or if it set lower until the computer thinks break-in is over.

Not trying to be a jerk but I know to take it back to the dealer but they are almost 3 hours away, their suggestion was put another person in the boat and I am going on vacation in 3 days.

Also, I have a feeling everything is fine and this is supposed to happen if you push it during break-in but I followed the book and if I stay below 4500 rpm it runs like a dream.

Thanks for reading this and I am open to any thoughts,
FF


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## bowhunter426 (Oct 20, 2010)

I would recommend getting a vessel view mobile to monitor what fault it is getting. Sounds like you went into Guardian mode. Any merc dealer should be able to diagnose. Rev limiter will limit your rpm from increasing above the set limit. It will "bounce" off of it, not slow down.

Here is a list of Guardian mode types

https://www.perfprotech.com/blog/ma...craft-and-guardian-system-warning-horn-alarms


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## Walley Gordo (Jan 21, 2005)

I just broke in 2 Suzuki motors this weekend. In my owners manual it says to not go over 3000 rpms going up and down for the first 2 hours. The 3rd hour up to 4000 rpms. The next 7 hrs. do what you want just don't have it in full throttle for more than 5 mins at a time.


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## bowhunter426 (Oct 20, 2010)

Walley Gordo said:


> I just broke in 2 Suzuki motors this weekend. In my owners manual it says to not go over 3000 rpms going up and down for the first 2 hours. The 3rd hour up to 4000 rpms. The next 7 hrs. do what you want just don't have it in full throttle for more than 5 mins at a time.


Mercury has a different procedure


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## kroppe (May 7, 2000)

fishnfever, this is a 2020 boat and motor and you have had it a short time, correct? What was your previous boat and how does the motor-hull setup compare? What is the trim configuration when the motor performs unacceptably?

Paint has no effect on a propeller in all normal situations. Your situation seems normal.


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## fishinfever (Feb 14, 2005)

Thank you all for taking the time to help me.



bowhunter426 said:


> I would recommend getting a vessel view mobile to monitor what fault it is getting. Sounds like you went into Guardian mode. Any merc dealer should be able to diagnose. Rev limiter will limit your rpm from increasing above the set limit. It will "bounce" off of it, not slow down.
> 
> Here is a list of Guardian mode types
> 
> https://www.perfprotech.com/blog/ma...craft-and-guardian-system-warning-horn-alarms


This is very good information, thanks.

I think it is possible that a sensor is bad or a control module needs to be updated (reprogrammed).
I just realized that in the video I cut the throttle as soon as I hear the alarm but when I first encountered this I didn't respond as quickly and the rpms seemed to drop then come right back up and repeat that until I cut the throttle back. Is that what you mean by bouncing?

Thanks, FF


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## piketroller (Oct 24, 2016)

The video shows the boat slowing significantly after running a bit at each speed test point, so it’s not clear this issue is limited to only 4500 RPM. At higher speeds the boat is also plowing very badly, so it doesn’t look like the trim is working properly either.

A trip back to the dealer should be the next step. Since you went with a dealer 3 hours away, hopefully the money you saved makes up for the extra time it will cost you.


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## kroppe (May 7, 2000)

@fishinfever Can you post 4-6 clear photos showing all views of the engine and transom, from inside the boat and outside, out of the water/on the trailer? In other words in your driveway or street.


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## fishinfever (Feb 14, 2005)

kroppe said:


> @fishinfever Can you post 4-6 clear photos showing all views of the engine and transom, from inside the boat and outside, out of the water/on the trailer? In other words in your driveway or street.


Thanks in advance. I am not certain what you are looking for so I went a little crazy. If you need something else I will get it for you.






  








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## fishinfever (Feb 14, 2005)

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Thanks again. If I hold the throttle still the rpms will drop considerably then jump right back to the high rpm and then cycle while I hold it there. Is that what you mean by bounce?

Thanks a lot, FF


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## bowhunter426 (Oct 20, 2010)

fishinfever said:


> A few more
> 
> 
> 
> ...


Yes, that would be bouncing. What is your tach connected to? Wireharness or plug wire?


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## fishinfever (Feb 14, 2005)

Okay, my previous boat was a Lund WC 14 DLX with a 15 HP 4 stroke Johnson. I think it is similar I think it is deep V or semi V. The Lund catalog says SVB. I literally just drove the boat for 13 years without any adjustment.

This new boat has power trim. I trimmed it all the way down then back up just a tiny bit past vertical. Just eyeballing it very close to vertical.

The tach pick up is just a wire wrapped around the #1 spark plug wire.

Thanks for taking the time to help me, FF


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## kroppe (May 7, 2000)

I'm looking at the static (fixed) trim. It looks like there is no pin/bolt in the bracket, or it is on the lowest setting. Combined with piketroller's comment about plowing, I would adjust trim.

Vertical can be hard to define on a boat in the water. Boats are stern heavy, especially a tiller. Tilt the motor up higher than you think you should, and adjust it in small increments while running at different set speeds. Get familiar with how tilt and trim work and how propellers and cavitation work.


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## bowhunter426 (Oct 20, 2010)

fishinfever said:


> Okay, my previous boat was a Lund WC 14 DLX with a 15 HP 4 stroke Johnson. I think it is similar I think it is deep V or semi V. The Lund catalog says SVB. I literally just drove the boat for 13 years without any adjustment.
> 
> This new boat has power trim. I trimmed it all the way down then back up just a tiny bit past vertical. Just eyeballing it very close to vertical.
> 
> ...


Get a tach that plugs into the wireharness or Vessel view mobile. If you are going to be keeping this boat for a while, Vessel view is worth it. You are likely reading low with that method and hitting close to 6000rpm because you are under proped what pitch prop is on the boat now?

Did Lund or the dealer mount the motor?


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## auger (Mar 6, 2013)

Did you change oil after break in? Make sure to go by manufacturers recommendations. Do not use full synthetic until those rings are fully set. Conventional oil helps heat the rings. Vesselview can also be linked to your dealer, so they can see exactly what you see as far as faults. Money well spent


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## fishinfever (Feb 14, 2005)

Last night, I got educated on trim adjustments and I now know I wasn't doing it correctly.
The dealer claims that Lund mounted the motor and they didn't record the rpm during the PDI.

I will get the Vessel View immediately.

The prop is a 13 x 17 4 Blade Spitfire. Now, this is where it all started. After the first time out, I thought it was the prop was the problem so I contacted the dealer and their response was put another person in the boat (we had 2) and Lund is always spot on.

If I use the Mercury Prop Selector I am too light to get a result but if I assume over revving (in the performance section I choose 5800 rpm) then it recommends 12.5 x 19 4 blade which I believe would drop my rpm by about 400. I tried other calculators that agreed. The Quicksilver calculator says 12.5 x 19 or 13 x 19 by weight.

I was inclined to believe that the motor was fine and just try a different prop but I didn't to start changing things without hard facts.

I haven't changed the oil yet. I think I am still in break-in period but I will keep that in mind.

I just remembered something that wasn't in the video. The first time this happened I was at WOT and the rpm was dropping dramatically then jumping back up then back down repeatedly and I held the throttle wide open and is was like fighting Hulk Hogan and scared the crap out of me. All other tests I have slowly worked up to the point where the alarm sounds and the rpm is cut and immediately cut the throttle.
I appreciate the help. Since I am leaving for the UP on the 20th, I may just hold off doing anything until I return. I will just stay below 30 mph. Then get the Vessel View and get serious about getting this fixed.
Thanks a lot, FF


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## auger (Mar 6, 2013)

My opinion, finish your break in process. It seems to reset after it faults out. I have the same motor. I never touched WOT in the first 2 hours of break in and if i did it was for a mere 10 seconds.


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## bowhunter426 (Oct 20, 2010)

auger said:


> My opinion, finish your break in process. It seems to reset after it faults out. I have the same motor. I never touched WOT in the first 2 hours of break in and if i did it was for a mere 10 seconds.


Mercury really wants the rings seated and encourages WOT during breaking

1. For the first two hours of operation, run the engine at varied
throttle settings up to 4500 RPM or at three‑quarter throttle, and at full throttle for approximately one minute every ten
minutes.
2. For the next eight hours of operation, avoid continuous operation at full throttle for more than five minutes at a time


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## fishinfever (Feb 14, 2005)

bowhunter426 said:


> Mercury really wants the rings seated and encourages WOT during breaking
> 
> 1. For the first two hours of operation, run the engine at varied
> throttle settings up to 4500 RPM or at three‑quarter throttle, and at full throttle for approximately one minute every ten
> ...


Yep, this is exactly what I have been trying to follow.

Installed VesselView Mobile. Seems to be paired properly. No Faults. Hours 2.1.
I hope to get out and test again this afternoon and I will report the results.
Thanks, FF


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## fishinfever (Feb 14, 2005)

I have completed my report.

First thank you for the advice regarding trim. I started out more than I thought it should be then brought it in slowly while on plane until rpm maxed also it just sounded right. The water was only splashing out about the last half of the boat.

I generated the same 2 faults 2 times at 4720 and 4790 rpm.

2011-23

Guardian

A particular state or condition exists.

Engine : STBD

6/17/2020 5:52:43

Engine Guardian is active. Power will be limited to prevent

engine damage.

Reduce engine speed.


2152-22

Manifold airflow

Relative to a specified threshold, the value is too high.

Engine : STBD

6/17/2020 5:52:47 PM

Mass airflow calculation is above limit.

Service engine soon.

That makes sense because the alarm information that you directed me to says

six beeps during a running failure Failure detected with MAP, MAT*, TPS or Flash Check Sum (ECM)

That pretty much sums it up. I appreciate the help but I think I am going to wait until I return from vacation before I address it.

FF


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## bowhunter426 (Oct 20, 2010)

Now you have proof it isnt a prop issue. Have fun on your trip. Any Merc dealer can address that issue


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## kroppe (May 7, 2000)

Sounds like a dealer repair under warranty.


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## piketroller (Oct 24, 2016)

Call up the closest dealer to where your vacation is, and see if they will do a quick reset of the ECM to get it out of Guardian mode. You might get lucky and be able to swing in on your way up there. Some dealers are really good at helping customers in a pickle like this. I had a problem with the starter on a Yamaha outboard on a Canada trip a decade ago. The dealer in the Soo on the Canadian side got me in and out, and I only missed an afternoon fishing, and that included a 90 minute round trip.


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## DirtySteve (Apr 9, 2006)

piketroller said:


> The video shows the boat slowing significantly after running a bit at each speed test point, so it’s not clear this issue is limited to only 4500 RPM. At higher speeds the boat is also plowing very badly, so it doesn’t look like the trim is working properly either.
> 
> A trip back to the dealer should be the next step. Since you went with a dealer 3 hours away, hopefully the money you saved makes up for the extra time it will cost you.


I bought a new boat with a mercury pro xs on it this year. Manual says to never trim motor the first 10 hrs of use. Trim has to be all the way down.


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## piketroller (Oct 24, 2016)

DirtySteve said:


> I bought a new boat with a mercury pro xs on it this year. Manual says to never trim motor the first 10 hrs of use. Trim has to be all the way down.


Which Pro XS? If you have the 115, it would be the same motor as the 75. There are a bunch of other different designs that carry the XS branding.


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## fishinfever (Feb 14, 2005)

I really got an education during this adventure and I appreciate all the help I received especially because it given with a positive and sincere attitude. 

I made wild leap in technology from my old 2004 15 HP Johnson with fixed trim to this new outfit with things I couldn't imagine.

The pin (trim) that the motor rests on when trimmed all the way down is missing. So, when I did trim it out I was starting lot farther in than I thought. 
One thing that I remembered. When I asked the dealer about a Transom Saver he raised the motor and removed the pin to show me where I could put a block of wood if I wanted. Clearly, he didn't reinstall it properly.

Strangely, the dealer is very interested in repairing this engine now that I sent them the faults.

Thanks again, FF


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## kroppe (May 7, 2000)

Strange that a dealer didn't take the opportunity to sell you a transom saver. It's uncharacteristic of a professional salesperson. 

I would get the motor repaired, at this dealer if there are no better options, then part ways with that dealer.


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## Shoeman (Aug 26, 2000)

I bet he's showing interest. Probably a nice chunk of money for warranty work and not just selling a prop


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## bowhunter426 (Oct 20, 2010)

piketroller said:


> Call up the closest dealer to where your vacation is, and see if they will do a quick reset of the ECM to get it out of Guardian mode. You might get lucky and be able to swing in on your way up there. Some dealers are really good at helping customers in a pickle like this. I had a problem with the starter on a Yamaha outboard on a Canada trip a decade ago. The dealer in the Soo on the Canadian side got me in and out, and I only missed an afternoon fishing, and that included a 90 minute round trip.


Guardian will reset itself when the issue is resolved.


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## fishinfever (Feb 14, 2005)

I don't think I was dealing with the A-team. Actually, I thought if I mentioned it he would throw it in but I didn't even know what they did. I had just seen them on larger engines.

Mercury is involved now and they are replacing the prop under warranty and encouraging having someone local do the repair and soon. They saw the video and are asking about the PDI and if it was operated at WOT before I picked it up. I didn't know what a PDI was until I found it in with the manual wrapped in plastic and blank. They may have a version on the computer but I didn't get a copy.

I think you can consider our ways parted and I have to confirm that I have the warranty because the first line in the warranty book under must be met to obtain Mercury Marine Limited Warranty is "Mercury Marine specified PDI process is complete and documented."
It also says "At Mercury Marine, every engine is operated and tested before it is boxed" hmmm.

Anyway , it has been a real learning experience. i would NEVER take anything home from anyone before riding in it or testing it first.

Good luck, FF


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## bowhunter426 (Oct 20, 2010)

fishinfever said:


> I don't think I was dealing with the A-team. Actually, I thought if I mentioned it he would throw it in but I didn't even know what they did. I had just seen them on larger engines.
> 
> Mercury is involved now and they are replacing the prop under warranty and encouraging having someone local do the repair and soon. They saw the video and are asking about the PDI and if it was operated at WOT before I picked it up. I didn't know what a PDI was until I found it in with the manual wrapped in plastic and blank. They may have a version on the computer but I didn't get a copy.
> 
> ...


The PDI is submitted to Mercury electronically with the warranty registration for motors sold separately. Don't know how it works for motors rigged by the factory. 

Enjoy the new boat


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## fishinfever (Feb 14, 2005)

UPDATE
I replaced the 13 x 17 4 blade with a 12.5 x 19 4 blade
Generated the same codes but at 36 mph and about 4500 rpm.
The Merc rep thinks they forgot to install a $3 part that restricts the air flow to allow the same equipment to be used for 75 -115 HP.
I have an appointment for 8/3 so we will soon find out.
Good luck, FF


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## fishinfever (Feb 14, 2005)

Last installment!!!
They installed the missing restrictor in the air intake
https://www.boats.net/product/mercu...MI5qWKnvOq6wIVgYbACh38lANiEAQYASABEgIgjvD_BwE
and now it runs WOT without any codes!
Good luck, FF


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## propbuster (Mar 4, 2004)

Great to hear it all worked out for you. So when the motor was built the needed part was not installed? Factory error?


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## fishinfever (Feb 14, 2005)

propbuster said:


> Great to hear it all worked out for you. So when the motor was built the needed part was not installed? Factory error?


Yes left out at the factory.
I am not an expert. My understanding is that the same basic engine is used for 75 - 115 HP and the restrictor is one of the parts used to achieve 75 HP.
Good luck, FF


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