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Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3728
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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I have a 2003 50 HP Mercury Bigfoot motor on a 20 foot

Customer Question

I have a 2003 50 HP Mercury Bigfoot motor on a 20 foot pontoon boat.
In neutral it will rev up to 6,200 RPM and set off the alarm.
It idles smoothly at 800 RPM.
On the lake under load (2 people) the maximum RPM is 3,400. I've been
told by mechanics that I should expect at least 500 RPM in the above
I've used a separate fuel tank and line with the same results. The plugs
are new this year.
I have a 14 inch prop. that I was told came with the motor.
Any suggestions would be greatly appreciated.
Ron McCakk
Submitted: 1 year ago.
Category: Boat
Expert:  Jason replied 1 year ago.

Hi Ron, my name is Jason.

All Mercurys are cataloged by serial number, can I get that number so I know exactly which engine you have?

Next, when was the last time it made full power under a load, what is the story behind the engine?

Have you done any diagnostic testing on your own yet, if yes, what have you done?

Customer: replied 1 year ago.
Please see the original question for what has been done and the prop is a 14RH13 Merc 3 blade.
Customer: replied 1 year ago.
I bought the boat and motor last year and it has never gone past 3,400 rpm.
Expert:  Jason replied 1 year ago.

I would still need to know which engine you have. Mercury makes 2, 3 and 4 cylinder 50 horsepower engines. They also make 2 stroke and 4 stroke 50 HP's. Which one do you have?

Have you done any compression or spark output testing?

Expert:  Jason replied 1 year ago.

Phone service is available in the USA, are you in the US or another country?

Customer: replied 1 year ago.
I live in Canada, the motor is a 4 stroke Bigfoot 50 HP. I have had the compression checked and all cylinders were tested and are good. I was advised that the plugs were fine but I don't know if they were tested for output.I'll be taking the boat out of the water for winterizing and I can get the motor serial number then. Perhaps we can finish this then.Thanks *****
Expert:  Charles replied 1 year ago.

Hello Ron, my name is***** will be taking over on your question if you still need assistance.

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