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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 10903
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I have a 1988 Hurricane 19 ft. deck boat with a Mercruiser

Customer Question

I have a 1988 Hurricane 19 ft. deck boat with a Mercruiser Alpha 1 4.3 L engine. My problem is that the engine starts and runs fine up until about 3,400 to 3,700 rpm, but if I try to push beyond that it immediately stalls out. Sometimes it will recover on its own if I throttle back quickly enough. I thought this was a fuel problem. I have replaced the paper fuel filter and I have cleaned the fuel screen that is in the fuel line just before the carburater (both were dirty) and tried new non-oxiginated gas. I also ran a can of SeaFoam through it with the fresh gas. I can't locate any other fuel filters, there is no water separator or fuel pump on this boat, and I'm out of fuel related ideas. I'm now thinking maybe there is a problem with the distributor-- that it is cutting out at higher rpms. Or possibly that a carb jet is plugged. Any ideas would be very much appreciated.
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.

Hello. My name is Tan.

You are on the right track with fuel issue. Run the engine on a different fuel source to eliminate the boat side fuel system. Disconnect the fuel line coming from the fuel tank at the engine. Plug the line. Now get some fuel line connect to the engine and stick the other end into a can of gas. Now run the boat does it run better?

This is a common problem with old boats and fuel tank that are contaminated with debris from years of use. The clue is the filters were dirty.

This will also tell us which is the issue the engine or the boat side fuel system.

Try this and post back with findings.

Customer: replied 1 year ago.
Hi Tan:Thanks for your suggestion. Here's what I have done so far. I removed the rubber fuel line and blew it from both sides with 90 lb of compressed air to verify that the line is clear. Then I screwed out the metal tube from the internal tank and verified that the pickup tube was clear. I found a one-way spring and ball valve at the tank, which was a bit sticky and had some debris in the spring. I cleaned all that out with carb cleaner, until it seemed to open freely (but it takes quite a bit of vacuum to do the trick).Next I got a jerry can of fresh fuel and stuck the now cleaned rubber fuel line into it. After running enough to be sure I was on jerry can fuel, I tried accelerating. There was some improvement, in that it would actually get to 4600 rpm now at WOT. But it still fades back to 3600 rpm and cycles back and forth every three seconds or so. A "water-ski" start will still lead to the engine dying. Does all this mean that something is stuck in the fuel system on the engine itself? Where should I look next? Thanks, Dave
Expert:  Tan replied 1 year ago.

The next place to go will be the carburetor. It is possibly full of debris. The debris is floating around the float bowl of the carb. We know the boat side fuel system is part of the problem. The only thing left is the carb and the fuel pump. The fuel pump can be tested with a fuel pressure gauge. The fuel pressure must be 5-7 psi at 1800 rpms. But most likely the carb is the issue as the engine run up to full throttle.

Is the fuel line stiff or does it rub off black in your hands?

I would rebuild the carburetor.

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