Mercruiser 4.3 L Throttle/RPM Problem

I was coming into dock yesterday and my boat stalled. I could not get it to run after that except in Gear at a higher RPM, it kept stalling out in neutral. NelsonQ and I looked at the throttle linkage this morning and everything was operating normally. We pulled off the air filter to see if it was stopping the airflow, it was not. The stamp on the air filter stated the motor should operate at 650 RPM in neutral, we made this adjustment on the idle screw.

The boat ran fine for most of the afternoon however after a couple of hours on the lake tubing and running it at about 3200 RPM when I put it in neutral it revs at 2000 RPM.

Hurricane 20 ft Fundeck
As stated the boat has a 4.3 L Mercruiser, Alpha One outdrive, looks to have an inline water separator and I had the Impeller replaced about 3 weeks ago by a marine mechanic.

If anyone has ideas as to what is going on please let me know.

Re: Mercruiser 4.3 L Throttle/RPM Problem

looks to have an inline water separator

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Ayuh,.... Welcome Aboard,... Change the filter,+ inspect the contents of the old 1 for Water...

Re: Mercruiser 4.3 L Throttle/RPM Problem

Thanks Bond-O. I changed the Fuel Filter last night and will put it in the water on Saturday. I am anxiously awaiting the outcome.

Re: Mercruiser 4.3 L Throttle/RPM Problem

There is another problem. The boat is backfiring when the boat is pulling a tube and the engine is up to operating temperature. It also backfires when accelerating pulling a tube, and accelerating over 3800 RPM's.

To that end I changed the Fuel Filter and I also ran a can of PowerTune through the Carb and filled it with High Test. The boat ran good for about 30 mins. and then when I came into the dock it wouldn't start. The boat didn't diesel this time however I am going up tomorrow to do some troubleshooting to see if I can figure anything out. After that I am going to pull it out and take it to a local dealer.

Re: Mercruiser 4.3 L Throttle/RPM Problem

To that end I changed the Fuel Filter and I also ran a can of PowerTune through the Carb and filled it with High Test.

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BUT, Did you ever check the contents of the old fuel filter for water? If you have a lot of water in the tank, it will fill up a new filter and the problem will be on going.