motor dies at WOT

[callide]

The motor is a 2006 30Hp Mariner with 40 hours on it.
The motor died at WOT but ran for longer times at 3/4 throttle but eventually died then too. I have renewed the o rings in the fuel filter and the fuel tank changeover mechanism. Problem exist when fuel is drawn from either tank.
originally the fuel bowl would continue to lower the more revs you gave it but now it is full when the motor dies
I have tried bypassing the primer bulb and the fuel filter. The carb has been removed twice cleaned thoroughly blown with compressed air.
Fuel pump has been renewed. all fuel lines appear in good condition
My conclusions if it was a spark issue than it would splutter at high revs and i should be able to recover by lowering the throttle this dosnt happen. Spark plug gap is correct
It must be a fuel problem in the carb itself.
If the needle and seat were worn out (not likley on a motor with this many hours than surely it would just flood the engine at any revs
After the engine dies I have to choke it to start indicating starved fuel
The butterfly's are at their correct position at WOT
I am at a lose and cant think of any other remedies except a carby kit.
getting the boat to a service agent is not a simple matter due to my location so i keep plugging away at it myself, but now its stop being a challenge and is damm right frustrating.

[scottar]

I think you are on the right track. I recently had a similar issue with a 15 Merc Super that turned out to be crap in the carby. At idle it would run all day but if you put revs on eventually it would suck in the gunk and come to a grinding halt. The only thing may be to try a tote tank with a totally independant fuel line if you have access to one just to confirm 100 percent that the issue is in the motor.

[Chong]

have u checked the pick-up in the tank??? has caught a few before??
C
C

[bluefin59]

My 04 60hp has a rubber diaphragm for the fuel pump on the motor that my service agent changes every year ,it's about $15 I'd be looking at that as we'll . Mine is a mariner and I have never had to use the bulb to get mine going in 10 yrs and 900 hrs ...Matt

[astro66]

mate....put new plugs in is always the first thing i do ....next set the timing and throttle to specs ... if its starving for fuel pump the bulb while your running...

[Fed]

Are the tank breathers open & clear?

[callide]

Tank breathers open - yes I have even run with the cap off the tank
Pumping the bulb - hard to do with no one driving the boat but i cant see that helping as the fuel bowl is full when it dies and it has a brand new fuel pump.
The fuel system has been simplified to a line connected directly from tank to engine
I have twin tanks and yes the pick ups are clear
Starving for fuel I believe is the cause I even tried running with the mechanical choke open from just a bit to a lot with no difference except having problems until the revs got high enough than the usual happens 10 to 15 seconds at WOT and she dies
Timing problem - possibly being a 2 stroke its mechanical and appears to move freely as the throttle advances adjusting this myself is out of the question as I don't have specs.
Spark problem - not likely as it has the correct voltage entering the CDI and the correct voltage entering the ignition module and a nice blue spark at the plugs.
I am taking the day off work to take it into a mariner service agent. Will let you guys know what the outcome is

[NArmstrong]

Should have to needles in the carby, one for idle and one for open throttle. Sounds like ur 2 needle is blocked. I had the same issue on mine. I could idle all day but at WOT it would die. Ended up just being the needle was blocked ( even though I had pulled the carby apart, I could get it clean enough

[JEWIENEWIE]

I had the exact same issue with mine stragiht after a service. Idles well, hlaf throttle all good, full throttle and she just died. Back to Mechanic and he found a tiny piece of shrapnel or rubber off a gasket or hose he reckons, blocking the needle. Very hard to find.......
JN

[callide]

Its fixed!!!!!!!!!!!!!!
Hats off to Scottar you posted the best solution only problem i didn't have a tote tank to try out your suggestion.
The mechanic ran it with my tank and observed the problem then connected an independent supply and all was OK
Half up the fuel line from tank to motor was a hard spot,when it was cut open this is the crud that come out as shown in pic.
Apparently the line had degraded over time most likely from lack of use from the previous owner.

271.jpg

[scottar]

Good news. Cheapest fix of the lot too. Bonus.