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1993 Mercruiser Alpha One

O

owensfarms

New member
Here's my issue...I have a '93 Alpha One. Last summer while out just cruising around, I noticed when I reached 2800 RPM that it started cutting out and trying to backfire. I could floor the throttle and it would not go above 2800 and would continue to cut out and backfire. I had at first thought it was bad gas even though I use Sta-Bil. I called one of the local marinas and they had me change out the fuel/water separator and look at the fuel in the filter and see if it was trashy, etc. I did that on Saturday and the gas was normal color and besides having some small particles, it was pretty much clean. I then thought it was not pumping fuel to the carburetor but after looking at, it is pumping plenty of fuel to it. I then took out one of the spark plugs and it is pretty black so I am going to replace them this weekend. After talking to others, they don't think it is a plug problem either. Their thinking is that it might be either the coil or distributor cap.

Any ideas, feedback or thoughts would be greatly appreciated.
 
Due to the low rpms and the issue that occurs I would suggest it is the ignition timing control module.


first thing to do is

disconnect the grey wire at the coil - this removes the tachometer from the ignition curcit.

re run boat if no change then reconnect wire.

next, when this occurs, the rough running, move the throttle lever back and forth very rapidly (like in the old days of "pumping the gas pedal" in a car).
this will increase the amount of fuel going into the motor and if the motor picks up and runs better even briefly then it is a fuel issue.
If no change then remove the flame arrestor and make sure the CHOKE butterfly is OPEN when the motor is warm up to normal temps.


if none of the above is wrong or makes the motor run any better or different then I would think it may be a ignition control module.

With the absence of the timing bieng able to advance a typical motor will get no more than 2200-2800 rpms max UNDER LOAD. Once the timing is advanced (by the ignition control module) the rpms will continue to rise to normal 4400-4800 rpms UNDER LOAD.

With no load the motor should/could rev up until it blows up.......

also check your gas tank vent........should be clear of bugs and spiders.........
 
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