300x help?

[F29DCB]

Just had an issue with my starboard motor and thought someone on here may be able to help me diagnose the issue.
Was running fine with both engines around 5800 rpm. starboard started losing rpm slowly, so I shut it down.
When I try to restart it turns over fine, ( no knocking ect.. )
Will not start without me applying a lot of throttle (as if flooded.)
Will only stay running at around 2K rpm for a while, then dies.
Lots of raw fuel and oil coming out of the lower exhaust port.

I removed all the plugs and there are no obvious fowled plugs.
Motor turns over freely with what feels like good pressure from each plug hole.

532188532189

[Frank Molé]

check TPS SWITCH

[F29DCB]

Thanks Frank, I do have an old spare TPS.
Is there a way to bench test them to verify they are working?
And do you think it would have gone bad while running fine down the lake?
It started fine when I left the beach and drove 10 miles at 5 to 6K throttle before it had an issue.


check TPS SWITCH

[Frank Molé]

Thanks Frank, I do have an old spare TPS.
Is there a way to bench test them to verify they are working?
And do you think it would have gone bad while running fine down the lake?
It started fine when I left the beach and drove 10 miles at 5 to 6K throttle before it had an issue.


look at the wires closest to the switch, thats were they brake...you can check it with a scanner easy also...or check the wires with a volt meter,5 volt referance,1 volt to 5 volts and 12 volt power

[F29DCB]

Thanks, will test the spare I have and replace it.
Boat is a 5 hour drive from me currently. Will not get a chance to get back there for a week or so.
Trying to be sure to have any parts I may need before returning.

[Frank Molé]

Thanks, will test the spare I have and replace it.
Boat is a 5 hour drive from me currently. Will not get a chance to get back there for a week or so.
Trying to be sure to have any parts I may need before returning.

ok cool,if needed you can always call me,number is in my sig....:thumbsup:

[F29DCB]

Frank, Isn't the TPS just an on or off switch that tells the ECU if it is at idle or is being throttled up?


ok cool,if needed you can always call me,number is in my sig....:thumbsup:

[Frank Molé]

Frank, Isn't the TPS just an on or off switch that tells the ECU if it is at idle or is being throttled up?

no it tells the ECM were the throttle is by voltage..... .0 to .5 at idle to 5.0 volts at wide open

[25two.stroke]

Check fuel pump screen in the vst, and check the ruel pressure regulator for a torn diaphragm. I had a bad regulator do just exactly what you are describing.

Bad lift pump diaphragm could do that as well.

[F29DCB]

Thanks,
great info.
Does the pressure regulator come apart to check diaphragm?
If not, how would I test it?
I was considering just swapping the whole fuel rail / injectors from the port to the starboard side to see of that is the problem.
Probably should just swap pressure regulators first.


Check fuel pump screen in the vst, and check the ruel pressure regulator for a torn diaphragm. I had a bad regulator do just exactly what you are describing.

Bad lift pump diaphragm could do that as well.

[25two.stroke]

Key up not running fuel pump should prime. With the vacuum reference line from the regulator off the air plenum see if it spirts fuel. If it does then the fuel pressure is blowing through the regulator diaphragm and dumps right in the intake. Remember that test for any and all fuel injected engines. You can also just pinch off that reference line but on 2 strokes with how much fuel they eat it can be hard to hear a difference.

[F29DCB]

532615Quick update.
I was able to get up to Havasu last week and do some diagnostics.
started with the throttle position sensor being the easiest and cheapest part to test.
Unfortunately that did not solve the issue.
Then went on to swapping out the whole fuel rail assembly from port to starboard engine.
She fired right up and idled fine. did it a few times just to be sure.
Brought both the fuel rails back with me to have all the injectors tested, cleaned, and calibrated.
Dropped it off at Teague Friday.
Mike called today and said all injector were working ok just needed cleaned and calibrated.
He then tested the fuel rail pressure regulators on a vacuum.
One was working properly, and the other was shot. probably a torn diagram.
Decided to replace the regulators on both motors to be safe.
Pricy little suckers though. $340 each. (highlighted in yellow on image )
Thanks to all for helping me out with this.
25two,stroke, you were correct with the pressure regulator.
And a big thanks to Mike at Teague for figuring out a way to vacuum test the regulators and find the issue.

[johnmiffco]

as stated test tps,.095 window at idle to 4.8 wide open ,,,,there is a nipple on fuel system to screw on a fuel pressure tester guage ,,,,could be a bad coil having weak spark need to ohm out coils,,,and a broken reed pedal will swirl extra fuel in the plenium to all cyls a stuck open injector,,,,, all these items will make motor flood with fuel

[25two.stroke]

,there is a nipple on fuel system to screw on a fuel pressure tester guage

This doesn't always tell you if you have a bad regulator. I've seen them have pressure within spec and still have a torn diaphragm. Just like what occurred to this gentleman's stbd motor. You don't need to vacuum test the regulator. There is no fancy deal to figure it out. If you just follow what I said in post #11 you would have found it instantly rather than swapping the whole rails back and forth and ultimately taking it to Teague.