Mercury 300R keeps cutting out

[hyperflow]

To make a very long story short, i been fighting with this motor since last june. It keeps throwing codes, so far its threw a camshaft encoder code, shift actuator code and a throttle demand sensor code. The symptoms are all identical, the only difference is the code.

I bought the bought to dealer(s) 7 times now. The sensors have been changed, some mulitple times. But the issue stays the same.

The motor will cut out at higher speeds,The motor will hesitate/hickup over n over. but not allways the same speeds, sometimes its 45mph, other time its 60mph and other times it will be 70mph,It seems if the boat sits for a couple of weeks the next time i use it it will be fine. But then the next day it will start cutting out again. It Also seems to do it worst when im in rough water.

The motor is also crazy hard a gas, I burn double what my friend burns with his triton walleye boat, I'm running a bullet 21SDC

The motor started doing this at 16hr last I now got 42hr ( mostly testing)

Any ideas?

[Pulsare2020]

To make a very long story short, i been fighting with this motor since last june. It keeps throwing codes, so far its threw a camshaft encoder code, shift actuator code and a throttle demand sensor code. The symptoms are all identical, the only difference is the code.

I bought the bought to dealer(s) 7 times now. The sensors have been changed, some mulitple times. But the issue stays the same.

The motor will cut out at higher speeds,The motor will hesitate/hickup over n over. but not allways the same speeds, sometimes its 45mph, other time its 60mph and other times it will be 70mph,It seems if the boat sits for a couple of weeks the next time i use it it will be fine. But then the next day it will start cutting out again. It Also seems to do it worst when im in rough water.

The motor is also crazy hard a gas, I burn double what my friend burns with his triton walleye boat, I'm running a bullet 21SDC

The motor started doing this at 16hr last I now got 42hr ( mostly testing)

Any ideas?

I'm sure Don will answer. "Worse in rough water...". My 300R had somewhat similar symptons around 50 hours, but not identical to yours and it did not throw any codes, but it did cut out, hiccup at higher speeds and it was running very rich. Don diagnosed mine quickly under warranty as having a defective injector wire (#7 cylinder I believe in my case). Has the dealer done a "jiggle test" on some of the harness wires? Anyway, after Don repaired the injector wire harness mine has run without issues since. It still smells rich at idle, but it has done that since it was new.

[mactlman]

will need serial number also posted

[nightbasser]

I would say the wiring harness. I've seen wiring harness cause all kinds of problems through the years and usually the parts cannon is thrown at the motor in question until the harness is the last thing to replace.

[Frikster]

Hi bud, i also have a 300R and had similar problem, after merc tried everything in the book , they disconnected the fuel line from the main tank and ran a separate tank with fuel in one hatch, to discover that there is a piece of silicone in the main tank that gets sucked up and basically starving the motor at random times as it blocks the flow into the motor , but is to big to go into the fuel system , creating all problems, i had to remove the tank and replace it with a clean tank and never had problems again.

Just something to look at, hope you get it sorted!!!

[EuropeanAM]

If you would, please take a moment to review the Announcements at the top of the Forum, and be sure to provide the Required Info (serial number) when posting. Thanks!

The "Symptoms" are likely ENGINE GUARDIAN. The PCM sets an "Available Power Threshold" when a fault is occurring. If you attempt to exceed that percentage, Guardian becomes active and begins limiting engine power in a last-ditch effort to prevent the engine from being damaged.

The underlying fault or faults are the CAUSE.

See if you can get FULL PRINTOUTS (current) from the G3 Diagnostic System, as well as the Serial Number.

[Capt James]

Check the wiring harness, on some earlier V8's there's an area it would get pinched near the cowling latch.