Mercury 4 stroke 50 Bigfoot Mid Range Miss (2001)

[Doindunes]

Hello,

I have posted before and now I will try again. I have what seems to be a common issue with these engines! Here is what is going on and what has been done.

1. Last July the engine started to miss or spudder at around 2,800 RPM. It starts fine and below 2,800 rpm is fine...also WOT is fine.
2. Spent 130.00 to have it diagnosed as carb issues. The marina ran an auxillary tank of gas to make sure fuel is fine and also CLAIM to have tested ignition.
3. Now I just paid 800.00 (plus you should count the last 100.00) to have the carbs rebuilt. I just put the boat in the water and guess what...the same problem! The marina tried to re-sync them and this did not solve the problem. So I spent all of this money and still have a broke boat! No they will not return any calls, but that is a different story as they want to nack track to the coil or stator.
4. The fuel has been treated since last year with seafoam.

Any ideas or thoughts on the coil or stator? I have my boat parked at a marina, so any work I perform has to be at the sand bar. I am ready to pull it and send it to anothe reoair shop. I have found many posts that are the same exact problem, but never post the fix.....

Thanks,

Dan

 

[verado7]

Re: Mercury 4 stroke 50 Bigfoot Mid Range Miss (2001)

try richening up the mixture screw a quarter turn each to the left - a lean idle mix will cause a leaner mix at midrange before the highspeed jets take over - the bench setting is just that -it needs a final adjustment on the water .

 

[Doindunes]

Re: Mercury 4 stroke 50 Bigfoot Mid Range Miss (2001)

Thanks for the reply! I will mention that to the mechanic, but I beleive that he already did this the day after I complained it was not fixed correctly. I am meeting with him today!

 

[Keith Richardson]

Re: Mercury 4 stroke 50 Bigfoot Mid Range Miss (2001)

I have a 2001 Mercury 50HP 4 stroke Bigfoot and am having the same problem. My motor starts great and runs great up to about 4200rpms and then will slow down or completely stop. The mechanic at the marina admits he is a better diesel and inboard mechanic than on outboards. He has consulted with other mechanics and they think it is the module. By the way, if I put it in neutral it will run great right up to 5000-6000 rpms without missing or bogging down.
Any help will be appreciated..

 

[Doindunes]

Re: Mercury 4 stroke 50 Bigfoot Mid Range Miss (2001)

They are looking at it again today! They bought some new software from Mercury to help troubleshoot the engine via the commications port. I will post when I find out what they tell me!

Dan

 

[kevinv]

Re: Mercury 4 stroke 50 Bigfoot Mid Range Miss (2001)

I have a 2001 Mercury 50HP 4 stroke Bigfoot and am having the same problem. My motor starts great and runs great up to about 4200rpms and then will slow down or completely stop. The mechanic at the marina admits he is a better diesel and inboard mechanic than on outboards. He has consulted with other mechanics and they think it is the module. By the way, if I put it in neutral it will run great right up to 5000-6000 rpms without missing or bogging down.
Any help will be appreciated..

having exact same problem with this engine any cure yet?

 

[Jeep Man]

Re: Mercury 4 stroke 50 Bigfoot Mid Range Miss (2001)

I purchased an '02 from a certified Merc technician. One of the upgrades he had done was change out the fuel pump because he said the older style had a problem with sputtering at mid throttle and shows up after a few years (more than 4) years of use.. The newer style doesn't have the problem . My motor is a 4 stroke injected model, but it sounds like yours may have the same pump.

 

[Doindunes]

Re: Mercury 4 stroke 50 Bigfoot Mid Range Miss (2001)

ok.......Nothing has been resolved yet! There was a delay in time and my money! They went through the entire ignition system and spent 8 -10 hours investigating and on the phone with many well seasoned Mercury mechanics and tech support. They replaced my intake o rings and now we are down to the next thing Mercury recomends. They recomend that I replace the crank position sensor as they have had issues with those. I have seen mention of that in posts along with the fuel pump. I will let evryone know how it is fixed...when it is fixed that is!

 

[plb2014]

Re: Mercury 4 stroke 50 Bigfoot Mid Range Miss (2001)

I had a 1999 40hp 4-stroke which is practicly the same engine. I had the exact same problem you are stating. My problem was the stator was shorting out at that particular RPM range. Go to the local mechanic and see if he can loan you a stator to try or find a used one. 2 years Before the problem started I installed a stator kit (that puts out more amps) on my outboard to charge my batteries. I just re-installed my old stator and it started running fine.

Thanks

 

[Doindunes]

Re: Mercury 4 stroke 50 Bigfoot Mid Range Miss (2001)

Thanks for the reply! I am still having issues and I just picked up a new crank position sensor that I hope to install this weekend. Next is the Stator. There are no boats at the marina that have a motor like mine to test out thos items before hand. They even offered to winterize and shrink wrap their boat for the use of it for a few hours. Everything else has checked out numerous times....so we will see. Hopefully it is one of those parts! I am just glad I usually just cruise out to the sand bar and not really need that particular rpm range! I just hate things that are not right!

Dan

 

[Doindunes]

Re: Mercury 4 stroke 50 Bigfoot Mid Range Miss (2001)

Sad to say that the new crank position sensor did not solve the problem. In fact I think it made it worse. Makes me wonder if I bought a bad part or it is just the original problem getting worse. I think I may try the stator....Will continue to post as the story goes!

Dan

 

[mwallek]

Re: Mercury 4 stroke 50 Bigfoot Mid Range Miss (2001)

Hi Dan,

I know its been a while but I have the same engine as you and just last weekend the same problem started with mine. Did you ever get to the bottom of your misfire problem?

Martin.

 

[Doindunes]

Re: Mercury 4 stroke 50 Bigfoot Mid Range Miss (2001)

Hi Martin,

Sorry I did not see this until now! I still have the same problem and since I last wrote...my mechanic gave up last week. I put a new stator, ecm, fuel pump, and the carbs done. Still acts the same way. I need to try and find a new mechanic that may have more experience, but I do not want to lose the boat for the rest of the summer.....Have you had any luck?

Dan

 

[mwallek]

Re: Mercury 4 stroke 50 Bigfoot Mid Range Miss (2001)

Hi Dan,
Sorry for the late reply, but I am back at work now and at my desk. Yes i found the problem with my engine just last week. My battery was faulty, firstly it was too big for the engine to charge and secondly it was not taking a charge. It was a 115ah. I changed this for a new deep cycle optimax 70ah and my engine now runs sweet as it did when it left the factory. I knew it had to be an electrical fault because the misfire was so precise when starting at 2000rpm and stopping at 3200rpm. I was starving my stator of its power.
Hope this helps
Martin.

 

[Doindunes]

Re: Mercury 4 stroke 50 Bigfoot Mid Range Miss (2001)

Gentleman...It was the carbs the whole time. I finally took my boat to Wilson Marine and they knew the problem in an hour...It now runs like a watch.