350 Merc Stalling out at higher RPM's

[saxman9801]

I have a 350 Mercruiser Alpha One that was fully rebult this last winter, it replaced a 1995 350 Mag (carbed motor). Motor runs great on the muffs and initally in the water runs great, after cruising for a little bit and increasing the rpm's it shut down on me just like it had ran out of gas. It tries to crank but does not catch, I let it sit for a few checked the fuel lines and tightend a connector on the carb and tagged the reset on the intake and it fired and ran all the way back to the dock great. I would appreciate any thoughts, when it stalls out I still have power to the key and it cranks over just fine, will this rule out the breaker on the intake? I also replaced the coil and anti-siphon valve since they were both old and I had them anyways. Thanks in advance for the help.

 

[gdombroski]

Re: 350 Merc Stalling out at higher RPM's

Did you change water seperator?

 

[saxman9801]

Re: 350 Merc Stalling out at higher RPM's

Yes water separtor was on of the first items I changed, before the above mentioned items on the water, I did take the water separtor off while on the water to verify it was full and then put it back on as well.

 

[searay3]

Re: 350 Merc Stalling out at higher RPM's

Check the fuel tank vent to make sure it is clear. If thats not the issue, try running on an outboard tank plumbed to the fuel pump inlet. There is a sticky at the adults only at the top of the page that gives a fuel system test. You also may be losing spark. When it dies, check for spark. This a carbed motor and what ignition? A little more ID info would help a lot..

 

[BIGALF]

Re: 350 Merc Stalling out at higher RPM's

This simulates a problem that I just had. Run a aux fuel tank and see if that works. My problem of a little strainer inside the fuel tank clogged and it ran fine at slow speed but starved at full speed and slowed down then stalled. The little screen cost me over $1,000 to find.

 

[saxman9801]

Re: 350 Merc Stalling out at higher RPM's

It is a thunderbolt 4, I checked the strain on the pickup and it is clean, I will verify the vent this evening. The anti siphon valve did seem sticky when it was removed, I have not ran it on the water since, just wanted to be armed with a few more things to look at when I take it out.

 

[Bondo]

Re: 350 Merc Stalling out at higher RPM's

Ayuh,... Did you check for Fuel,+ Fire when it was Down,..??

You said there was fuel in the filter,.. What about the Carb,..??
Spark at the Coil,..?? at the Plugs,..??

 

[saxman9801]

Re: 350 Merc Stalling out at higher RPM's

Checked for fuel when down did not have a means for checking for spark with me. Took it out tonight and still have the same problem, there is gas in the filter and gas up to the carb in the line, some fuel does come into the carb when I depres the throttle though it apprears to not be a ton. I do not think it is spark related as when it happens it acts like it is running out of gas. The problem seems to occur most after turning a sweeping corner, as I increase the throttle to keep the speed up coming out of the corner sometimes it will then stall out. The first time it happened tonight i went back and pulled off the water separtor and cracked a fuel line coming up to the carb and then after a minute it fired right up, drove it some more and same problem again. I pulled two plugs right after the problem occured and they are both lean, just too white. I appreciate the help and the responses.

 

[saxman9801]

Re: 350 Merc Stalling out at higher RPM's

I wound up draining the gas out and nothing looked too bad, I filed it back up with some fresh gas and some HEET and then also emptied out the fuel water separator. While it was down I took the carb of and dumped the gas out of it, it was a dark yellowish color? Anyways I sprayed the entire carb out and got it cleaned out. Put it back on the motor and ran it for a bit on the muffs and the took it down to the river. Fired right up and ran great nice and smooth and most importantly NO staling out! Few questions, should I look at rebuilding the carb anyways or possibily replace it? The carb is off the original 1995 350 Mag, it did have the highrise intake, I am not sure if it is the 600cfm Weber or the larger one.
My new motor is a 300HP 5.7, and I replaced the stock manifold with a performer by Edelbrock. Would the 1409 (600cfm edelbrock) be enough for this motor? Thanks in advance for the help.