1991 Mariah PCM 351 stalls after a few seconds

[joe Schnur]

Replaced fuel filter fuel pump still runs and roughens up and stalls. Please give me some where to look. Thinking about looking at replacing the fuel lines next .

No leaks pressurizedk tank and no leaks.

Don't have access to no ethanol fuel. Could this be causing an issue adding cd2 lead substitute.

Thanks in advance

[Wulphie]

Check the easy stuff first. Look down the throat of the carb, if the floats are stuck it will be leaking fuel and flooding the engine. Very common with the Holley carbs.

[joe Schnur]

Doesn't seem to be flooding seems to be starving

[Wulphie]

That is easy to verify. Is the accelerator pump squirting fuel?

[chris young]

Is this an idle only problem? Will the motor run at higher RPM?

[NorCalPR]

Might sound simple, but I had a buddies boat that the fuel screws backed out and were 4 turns out.

After adjusting, it ran like a champ.

Worth double checking. Turn the screws in and count the turns. Back it up the same amount if around 2

Both screws should be the same

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[joe Schnur]

Will try the screws it is not just an idle issue I rev the engine to keep it running it eventually dies. Yes initially the pump will squirt fuel.

[Wulphie]

Will try the screws it is not just an idle issue I rev the engine to keep it running it eventually dies. Yes initially the pump will squirt fuel.

If the accelerator pump will only squirt fuel once check that the linkage is following the cam properly. It is common for the shaft to get corroded and the linkage does not follow properly. The lever will stay in the depressed position. If the linkage is functioning properly you need to get into the guts of the pump. If that all checks out then you most likely have a fuel supply issue.

[joe Schnur]

Accelerator pump always works. Cut 1.5 inches off each end of the hose . Blew out the check valve on the tank retightened everything engine runs rough probably due to the hose being stretched over the edges of the tank.

Two more pieces of info
1 The rpm gage bouncing around a bit may have been due to the rough run but seemed a bit off from what I expected the RPGs to be.

2 The spring in the valve on the tank seemed a bit stiff.

3 The fuel light is on but there is plenty of fuel in the tank?

Ok wise fellow users help me get back on the water

[joe Schnur]

Still not working

Pulling and rebuilding carb

[joe Schnur]

Well carb rebuilt still no joy

[chris young]

Curious, if the carb is rebuilt and you're sure you're getting fuel, my next suspect would be a vacuum leak. Your PCV could be stuck open. I'd pull the hose off the carb and plug the inlet. How did the problem manifest? Was the boat running fine and now it's not? Will it run if you leave it in neutral and keep the thottle up? I think someone else had a very similar problem and it turned out to be a collapsing fuel hose. I'd suggest running a brand new hose from the fuel pump into a gas can and that eliminates that possibility. How long does it run before it dies? It should run about 15 seconds on the fuel bowl. If you've got a really restricted fuel flow for whatever reason, I would suspect that after it dies, you would have to crank it for several seconds before it will start again. An easy way to check that is to take the flame arrestor off, run it until it dies and then check to see if the accelerator pump is still pumping fuel without re cranking. If so, I'd say it's not a fuel starvation issue.

[joe Schnur]

Thanks Chris new hose in place 6 to 10 secs idled to the end of lake after a weekend of skiing pulling a barge. On drive back to the dock it just would not stay running and killed the batt trying to start tried a spare batt no joy .

[joe Schnur]

Thinking about coil just frustrating in garage now. Will take to shop in march if I get no new ideas

[chris young]

So this seems to be a random issue? The only other thing I can think of would be your electric choke is not working correctly.

The boat would start normally cold, but once the engine was warm it would be very hard if not impossible to start, and wouldn't want to keep running at low RPM. While you're skiing it would run pretty well off the secondaries, just rich but still lots of power. This one is pretty easy to test, just turn the key on and leave it on for a while and check to see the choke opens and stays open. I'd leave it that way for a couple of hours and check it every 10 or 15 minutes.

Good luck

[joe Schnur]

Rebuilt carb had to adjust the idle screw way down the engine was pulling gas through and flooding also had to replace the floats with brass ones