Mercruiser 5.7 mystery

[Petethegreek]

Hi folks,
I hope someone can shed some light on what is going on with my 5.7.
A few weeks ago I tried to start my port engine, it started to turn over, went bank and stopped. When I tried again, no sound, but the voltmeter on the dash went to zero. Tried again, same thing, voltmeter to zero. I called my mechanic and he was booked up for the next three weeks. He suggested let it sit for a while and try again. After a week, engine would turn over very slowly. After another week, would start, but I had to keep pumping the throttle or it would die. My mechanic finally showed up, fiddled with the carb and now runs like normal. I checked the oil today and it is a little higher than the last time. Can anyone tell me what is going on? The engine is a Merc remanufactured and 5 years old with about 230 hours. Any help would be greatly appreciated!
Thanks, Pete

[mmwjr]

Oil level only increases from either water intrusion into the cylinders that gets past the rings or to rich on fuel which gets past the rings. A misadjusted carburetor doesn’t impact the ability of an engine to turn over just start. Was the engine cranking but not starting or not cranking. If the later I would check the condition of the battery and battery cables on both ends. The negative cable can come loose on the block.

[Petethegreek]

Mike,

At first it wouldn’t even crank, no sounds, just the voltmeter bottoming out. I’ll try tracing the engine ground.

One of the ‘experts’ on my dock told me I shut down the engine wrong by just turning off the ignition. He says you have to rev the engine for a few seconds and then turn the key off. Is that the correct way? I call him an expert, but his engine hasn’t run in years.

The engine was running rich, you could smell gas at the back of the boat.

Thanks for the help!

Pete

[mmwjr]

Originally Posted by Petethegreek

Mike,

At first it wouldn’t even crank, no sounds, just the voltmeter bottoming out. I’ll try tracing the engine ground.

One of the ‘experts’ on my dock told me I shut down the engine wrong by just turning off the ignition. He says you have to rev the engine for a few seconds and then turn the key off. Is that the correct way? I call him an expert, but his engine hasn’t run in years.

The engine was running rich, you could smell gas at the back of the boat.

Thanks for the help!

Pete

Pete

I disagree with him nor do I see how that would have any impact on the engines ability to crank over which is purely an electrical thing. If battery and wires are good I would replace the slave solenoid as it’s common for these to get resistive limiting current flow and causing a voltage drop to the starter solenoid.

[Trey5684]

I had a similar slow cranking and then no cranking and voltmeter dropping to bottom of scale, turned out to be bad starter with a heavy amp draw. First as suggested check all wiring and connections, I don't know if a loose connection would cause a voltage drop. However follow Mike's advice he's usually right.

[mmwjr]

A loose connection like a corroded one does add resistance to the connection and a voltage drop will occur.

[Derby Time]

I'm guessing the "expert" was referring to shutting down while moving and the engine was partially hydro locked due to water backing up past the flaps and risers.

[Petethegreek]

Derby Time,
Now that I think about it, the boat was moving backwards very slowly (maybe 2 feet or so) when I backed into my slip and shut down the engine.
Thanks, Pete

[mmwjr]

Originally Posted by Petethegreek

Derby Time,
Now that I think about it, the boat was moving backwards very slowly (maybe 2 feet or so) when I backed into my slip and shut down the engine.
Thanks, Pete

If water ingestion occurred you can verify by removing the spark plugs to see if water comes out. However being that you were in the slip I doubt there was enough momentum to force water up the y-pipe and past the flappers to get into the engine.

[Derby Time]

I would agree that it's unlikely this is the issue. Just thinking through what the expert was talking about. I can see how the description of what happened could have put him on that train of thought. Hard/no cranking initially that improved as it sat due to water pressure leaking down.