Old Mercruiser I/O missing, runs rough

[John3]

My Boat has a 160 HP, 1967 Mercruiser I/O (Chevrolet Straight 6 block). I recently replaced the Mercruiser Voltage Regulator with an Automobile Voltage Regulator. It ran well for several outings. Last week after a couple of days of satisfactory use it started running rough and missing at cruising speed and would not idle. I was at a loss as to what caused the problem although it seemed electrical rather than fuel. I have 2 fuel pumps hooked up and it was running on the electric pump. I switched to the mechanical fuel pump, still ran rough. However, with the key on, the elect. fuel pump was still trying to run even though my fuel line valves were now blocking its flow. I disconnected the electric Pump from the accessory connection on the Voltage Regulator and the motor ran OK again.
Question: Is there something special I should look for when replacing the Voltage Regulator? Or, am I missing something? Could the real problem be somewhere else in the Electrical System?

 

[Bt Doctur]

Re: Old Mercruiser I/O missing, runs rough

much easier to go to the single wire GM marine alt. 1 hot, 1 ground. everything else is internal. Electric pumps must be wired thru a pressure switch, not the acc. wire.

 

[John3]

Re: Old Mercruiser I/O missing, runs rough

Thanks for the input. Any thoughts as to what caused the problem?

 

[Kainon]

Re: Old Mercruiser I/O missing, runs rough

I think you may have been running too much fuel pressure to the carb, thereby flooding the engine. ( did you see any black smoke ).

You need to have 9v at the Coil while running, when the starter ciruit kicks in, you should see 12v.

As mentioned, I'd go with a 1 Wire Alt ( actually mine has a 2 wire ( 1's a ground ), a Pertronix Ignition Kit, and a good Carb Rebuilding. I prefer the Mercruiser Carb kits over Sierra Marine or Napa ( same as Sierra ).

Feel free to PM me..

 

[John3]

Re: Old Mercruiser I/O missing, runs rough

Nah, I don't think it's running rich. No black smoke and if it were the missing would have stopped when I switched to the mechanical fuel pump (It's the original type for my engine). However, missing stopped only after I disconnected the elect pump at the voltage regulator.
Had the carb rebuilt a couple months ago. It's clean.
Guess it must be some sort of feed back from the electric fuel pump through the voltage regulator accessory connection. If that's it then isolating the elect pump is probably a good idea. Think I'll try hooking it up through an oil pressure switch.
Don't know why I'd want to get a new Alternator. The one I have is running fine.

 

[fishinpa]

Re: Old Mercruiser I/O missing, runs rough

Have you run the engine and checked the voltrage (charging voltage ) at the battery ?



fish

 

[lonemust]

Re: Old Mercruiser I/O missing, runs rough

The electric pump should have never been hooked to the regulator. It should always go through a oil presssure safety switch.