2006 Mercury Bigfoot 50hp 4 stroke Outboard Motor

pclark

pclark

Well-known member
I purchased a pontoon boat from my elderly neighbor a couple of years ago. The motor, a 4 stroke, i thought would be awesome but it's never ran quite right, just can't seem to get the RPM's where they should be. It runs like it has a fouled plug, very boggy. Before I put it away and winterized it last fall I changed the plugs hoping when I got it out and filled it up with a fresh tank of premium gas it would run better. No such luck, however, on our way back from dinner about a month ago we were cruising at about half speed and it just kicked in and ran perfectly, just like it should. I was encouraged to say the least. Next time out it returned to it's not normal boggy performance. I did prime the bulb on the fuel line before I went out next time and it ran perfectly until it was time to slow down or stop somewhere and it bogged down again. Checked fuel filter, the gas line is brand new, the bulb is brand new, yes, it is installed correctly. If I prime the bulb before using it runs perfectly until i stop and then it bogs down again. By running perfectly it tops out at about 5800 RPM's and by bogging down it runs at about 4200 RPM's. I talked to a local mechanic who I respect and he said it most likely the carburetors that need to be torn apart, cleaned and rebuilt (cost $600-$800, about a six hour job) I have researched forums on this particular motor and found that a lot of people with the same motor experience the same symptoms, It probably didn't help that the neighbor only used it about 4 times during the summer and it sat the rest of the time. The boat is a 820 Sylvan with onboard fuel tank in perfect condition. Any suggestions or guidance is appreciated. Thanks!
 
bearrassler

bearrassler

Well-known member
Merc switched from carbs to EFI for the 2003 models so if you have carbs it is a little older motor. When I was in the boat business years ago we had problems with carbed four strokes of any brand. The jets are so small that they were constantly getting plugged up.
 
pclark

pclark

Well-known member
bearrassler said:
Merc switched from carbs to EFI for the 2003 models so if you have carbs it is a little older motor. When I was in the boat business years ago we had problems with carbed four strokes of any brand. The jets are so small that they were constantly getting plugged up.
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Thanks Berarassler, I wasn't sure if it was carburated or EFI but you cleared that up for me, it's a 2006 so EFI.
 
pclark

pclark

Well-known member
arctic1 said:
did a little poking around, check this thread out https://continuouswave.com/ubb/Forum3/HTML/021134.html#:~:text=I have owned [2006 Mercury,just before I purchased it.
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Arctic1, thanks for the link and the forum. It is becoming increasingly apparent that these motors are very finicky and need to be maintained almost 24/7, very hard to do where I live because it is used for about 5 months of the year and stored for 7 months. I have always tried to maintain my boats/motors, snowmobiles, snowblowers, lawn equipment, seasonal recreational motors by only using premium, non-ethanol gas, treatments, regular oil changes, lower unit every year, plugs, wires, etc. but his Mercury really has me baffled. I will do the VST maintenance and see if that works. I did take it out yesterday and primed the bulb before starting and it ran perfectly the 20 minutes or so that I had it out at high RPM and lower RPM. I expected more from a 4 stroke to honest, an due to the performance of this one I would not purchase another Mercury outboard motor. I have a 2006 Yamaha 150 EFI and it just runs great all the time, very impressed, in fact, on our chain of lakes, Yamaha is quickly becoming the most popular outboard motor.
 
E

euphoric1

Well-known member
Paul, if its running doggy and all of a sudden like a switch it has full power and lose it just the same I would suspect more that it is a loss of ignition. A dirty carburetor will not all of a sudden have full power and then not in my experience. if when you start if it is verry doggy try disconnecting one of the spark plugs and restart it, if it runs, reconnect and disconnect the other and see what happens, or if you know someone with a clamp on or inductive tachometer you may be able to tell if coil is dead or not as well, but have had failed coils still send signal tach will pick up. to determine if fuel problem remove air box cover, use carburetor cleaner and spray into throat of carburetor and see if runs better, don't use starting fluid, do not need something that volatile. But from what you are saying how all of a sudden it has power leads me more to ignition problem. BTW.... stick with the Mercruiser fuel additive, yes expensive but better than seafoam IMO, seafoam had its day once.
 
pclark

pclark

Well-known member
euphoric1 said:
Paul, if its running doggy and all of a sudden like a switch it has full power and lose it just the same I would suspect more that it is a loss of ignition. A dirty carburetor will not all of a sudden have full power and then not in my experience. if when you start if it is verry doggy try disconnecting one of the spark plugs and restart it, if it runs, reconnect and disconnect the other and see what happens, or if you know someone with a clamp on or inductive tachometer you may be able to tell if coil is dead or not as well, but have had failed coils still send signal tach will pick up. to determine if fuel problem remove air box cover, use carburetor cleaner and spray into throat of carburetor and see if runs better, don't use starting fluid, do not need something that volatile. But from what you are saying how all of a sudden it has power leads me more to ignition problem. BTW.... stick with the Mercruiser fuel additive, yes expensive but better than seafoam IMO, seafoam had its day once.
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Thanks Brian
 
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