60 HP Mercury 4 stroke cutting out when cruising

[jeffro636]

Hi, serial number 1c1 50827
Bought 2011 boat and motor and prior to purchase had it checked out at local boat dealer. Boat had sat for a year. They said motor had 25.5 hours and recommended oil change, lower unit fluid and water pump.I did that.

Then I siphoned out fuel and replaced with ethanol free fuel. I idled it for 15 minutes with muffs and replaced both fuel filters.

Took boat to lake and it popped right up on plane and ran for a couple of miles and then started cutting out and revving back up with rpm's jumping between 6000 and 4500 or so. If I come to a stop and turn motor off or just idle and get back on plane it takes a mile or so before it begins again.

Thought it might be electrical so I replaced the plugs. No change.

Any ideas? Thank you in advance.

Jeff

[Kodiak16]

Check your fuel lines. could be collapsed on the inside. Fuel filter as well.

[jeffro636]

Check your fuel lines. could be collapsed on the inside. Fuel filter as well.

Checked fuel lines when I replaced the fuel filters. Removed both ends and looked inside with flashlight. Did not replace. Is 2011 fuel line with blue lettering, alcohol resistant.

[berudd]

Is it cutting out like its not getting spark or is it more of a bog?

[jeffro636]

Is it cutting out like its not getting spark or is it more of a bog?

Seemed to me to be spark, that is why I replaced the plugs. Idid general maintenance on my old boat with carbs and points but am no expert. Worked on my own cars for the last 40 years until that became almost impossible, but am no expert.

[jeffro636]

Ran boat at 4500 rpm's for about 5 miles and no cutting out then increased rpm's to 5800 and after half mile started cutting out again. Reduced rpm's to 4800 and went 2 miles without cutting out. Just do not know.

[berudd]

I had an Evinrude back in the day that had a bad coil and it sounded like a switch being switched off and on. Just guessing at that. When you replaced the plugs, did one of them look blacker than the rest?

[jeffro636]

I had an Evinrude back in the day that had a bad coil and it sounded like a switch being switched off and on. Just guessing at that. When you replaced the plugs, did one of them look blacker than the rest?

Nothing I thought odd.IMG_20190416_141512.jpg

[berudd]

Nothing I thought odd.IMG_20190416_141512.jpg

Agreed.

[jeffro636]

Going to replace the fuel line and bulb and put the boat back in the water in a week or two

[jeffro636]

I replaced the fuel line and primer bulb with Mercury parts
Split the fuel line I removed ,(2010 low perm blue lettering) and then cut into 2 inch pieces. There were a couple sections in a row where the lining slipped out.
No melted or deformed lining, just easily removeable.
It seemed like enough to collapse under suction, so hopefully that was the problem.
I'll get the boat in the water next week and find out
Thanks for the suggestions

Jeff

[jeffro636]

Well it must have been the fuel line inner liner collapsing causing the cutting out at high rpm's. Ran 5 miles at about 5900 rpm's and no problems. The fuel line was 2010 low perm. I think that was the first year for the blue lettered line.
Has anyone heard of the liner separating. I wish I had taken pictures.

[SilverFox579]

It's possible if not installed properly, there's a topic about this in the 3L forum FAQ that applies to any engine - FUEL LINES AND PERFORMANCE PROBLEMS

[jeffro636]

It's possible if not installed properly, there's a topic about this in the 3L forum FAQ that applies to any engine - FUEL LINES AND PERFORMANCE PROBLEMS

Well I read that thread and it seemed like it was about older fuel lines or 8M primer bulbs that caused problems. My lines were alcohol resistant lines with blue writing and I did not have a 8M bulb with non oetiker clamps. There was no visible deterioration or liner separation at the connections to the tank or motor. It was the original line on the boat.
How would improper installation cause liner separation?
Thanks
Jeff

[EuropeanAM]

Ran boat at 4500 rpm's for about 5 miles and no cutting out then increased rpm's to 5800 and after half mile started cutting out again. Reduced rpm's to 4800 and went 2 miles without cutting out. Just do not know.

Connect a SEPARATE, Portable fuel tank and line DIRECTLY to the engine. Run the boat and see if the problem continues, or ceases.

[SilverFox579]

Well I read that thread and it seemed like it was about older fuel lines or 8M primer bulbs that caused problems. My lines were alcohol resistant lines with blue writing and I did not have a 8M bulb with non oetiker clamps. There was no visible deterioration or liner separation at the connections to the tank or motor. It was the original line on the boat.
How would improper installation cause liner separation?
Thanks
Jeff

Might have been a bad batch, all that matters is you replaced the line and problem is resolved.

[EuropeanAM]

Inner and outer liner are chemically bonded, if you push the line onto a barb (stretching the opening), it's very easy to pull the liner loose at or near the end. This may not present right away, either.

And as with any hose or line, time and exposure to fuels eventually deteriorates the line. 9 years isn't too bad.

[jeffro636]

Thanks again for all the replies
Jeff