Help! I need more RPMs - 2006 60hp Merc Bigfoot 4-stroke

[JoeCozmo]

I have a 2006 60hp Merc bigfoot 4-stroke on a Suntracker pontoon. Since I bought the boat, it has only managed to turn about 3800-4000 rpms at full throttle. Occasionally, out of nowhere, it will jump up to about 5200 rpms and run like this for a minute or two, then go back down to 3800. I think 5200 is where it should be at full throttle.

The engine runs smooth at 3800. I have replaced the spark plugs, fuel filter, fuel hose and primer bulb. This hasn't solved the problem. If I had bad plug wires, or only running on 3 cylinders, I would think it would be running rough.

When I open the throttle in neutral, it will turn up to the red line level every time. It is only when I am in forward, that I struggle with this situation.

Any suggestions on what I should try next?

Thanks!
Joe

 

[racerone]

Re: Help! I need more RPMs - 2006 60hp Merc Bigfoot 4-stroke

Most motors will rev up it nuetral , this means nothing.-----------What you need to do is hook up a timing light and observe the spark.----You might be running on 3 cylinders most of the time.

 

[Arkyhunter46]

Re: Help! I need more RPMs - 2006 60hp Merc Bigfoot 4-stroke

It sure sounds like you are running on three cylinders. Could be a number of things. Could be ignition or fuel. In my experience a fuel problem doesn't come and go like an ignition problem can. I would pull the spark plugs out and look at them carefully. One will probably be extremely clean and wet. That will be the cylinder you are losing. Your engine probably has coil packs instead of a switchbox that work each cylinder independently. If that is the case and you have access to a sparky to check the fire you can isolate the problem. If not then hook a timing light to each plug wire and see if it flashes. If you have spark on all cylinders then move to the fuel system. Again, look at the plugs and find the odd one. That will be the likely place to start.

 

[JoeCozmo]

Re: Help! I need more RPMs - 2006 60hp Merc Bigfoot 4-stroke

Thanks for the replies guys. I'm planning to pull the plugs this weekend and do some checks.

 

[JoeCozmo]

Re: Help! I need more RPMs - 2006 60hp Merc Bigfoot 4-stroke

Finally got my issue taken care of. It turns out that I had a bad ignition coil on cylinder #1. Mercury has issued a recall on some of these coils because they are defective. If anyone has a similar problem, see the link below for info:

http://***********************/Merc... Coil Service Repair Bulletin No. 2009-26.pdf

My local Mercury dealer exchanged all four of them for free! Now I'm running on all four turning about 5400 rpms. Much better!

 

[Shotgundanny]

Re: Help! I need more RPMs - 2006 60hp Merc Bigfoot 4-stroke

Sounds exactly like my problem, although my engine isn't revving up randomly.(just lost about 1200 rpms since december when i ran it last) I put new spark plugs in and ran the boat for about ten minutes. When I pulled the plugs out, it looked like #2 was still clean and the other three were soiled. I just spent close to $300 bucks getting the injectors and vst tank serviced and cleaned. Now to check the coils. Thanks Joe, I couldn't bring up that PDF you posted. I'll call the dealer. I have the same year and model motor.