4.3 Mercruiser stalls after a few mintutes.

[proline2550]

Just put my twin Mercruiser in after rebuilding the heads and re-ringing both engines after an exhaust shutter problem last year hydrolocked both engines on several outtings. With new fuel filters and all new ignition components, they both tested fine when run with the muffs on. While running slow and checking for leaks, I noticed the starboard side riser leaking and tightened the clamps. No more leak, but no more power either. After the repair, I got on plane and the starboard engine began to lose RPM and then quit after a half mile at 2300 RPM. Both engines ran at idle fine on the return trip to the slip. (a no wake return) The port engine runs flawlessly. Last night, I went down and removed the filter to find no debris or water,I replaced it anyway. I then swapped fuel pumps (electric) the problem didn't move to port. I removed the easiest shutter and again ran it to another stall within a minute or two. The engine spins freely, no evidence of liquid in the cylinders, after the engines stalls, I have good accelerator pump squirts, the choke pulloff is working properly, A vacuum guage test showed 20 inches of steady vacuum at 1000 RPMs, I keep thinking exhaust restriction, not fuel starvation. I meant to run the port side fuel hose to starboard just to eliminate a blocked hose, but forgot the stuff on my work bench.The problem remains with the fuel cap off so I eliminated a restricted vent. I am a mechanic by trade and have seen a lot of weird problems on gas, diesel, and propane systems but this one is trying my already limited patience. Put your thinking caps on guys, did I miss something?

 

[Don S]

Re: 4.3 Mercruiser stalls after a few mintutes.

Did you ever look down in your drives and exhaust Y's to make sure the old exhaust shutters weren't stuck in there and blocking the exhaust passages? It's happened before!

 

[bamaboaters]

Re: 4.3 Mercruiser stalls after a few mintutes.

What year engines ?

 

[proline2550]

Re: 4.3 Mercruiser stalls after a few mintutes.

They are 94 vortec engines, and good thought. I'll try and get in to see if I can find it. Only one had come apart, but it was the port engine. Goin to work now, check back later.

 

[Bondo]

Re: 4.3 Mercruiser stalls after a few mintutes.

Only one had come apart, but it was the port engine.

Were All the pieces Found at that Time ???

 

[bamaboaters]

Re: 4.3 Mercruiser stalls after a few mintutes.

My 99 4.3 was doing this and found the oil switch to be the problem. Engine would stall, then after sitting floating downstream, fire up again then run fine for hours, then repeat process.

 

[proline2550]

Re: 4.3 Mercruiser stalls after a few mintutes.

Just got back from the boat, switched fuel feed lines and carbs, I had to go through the motions. Problem is still with the starboard engine. Hauling it out on Sunday to pull the y-pipe and flip it upside down so I can hopefully watch whatever is there come out. I'll post my findings, thanks so far guys.