Merc 5.0L V8 wont start

[scott0987]

Hello, I have a 2000 Bayliner with a Merc 5.0 L GM V8. It ran perfectly all summer, never gave me a single problem. Two weeks ago I pulled it out for the winter I hooked up the muffs and ran it in the yard to flush the motor. A week later I began to winterize her, I put the stabilizer in the gas ( I put in alittle more then the bottle called for, the bottle treated 80 gallons and my tank is 65) I fired her up, the motor started right up and ran for about 30 seconds, the for about 15 seconds it ran very rough then finally shut down. I was then unable to get it started again. My first thought was I put in to much stabilizer so I disconnected the fuel line and tried to run it off a bottle of straight gas and still nothing. The motor is firing and burning gas because when I turn the key is fires a time or two and you can see exhaust exiting the prop so I know its burning, its just not catching and starting. Anyone have any ideas??????

 

[Don S]

Re: Merc 5.0L V8 wont start

Carbed or EFI?
If carbed, does fuel squirt into the throttle bores when the throttle is pumped?
Have you checked your fuel filter for water?

No, the stabilizer didn't cause the problem
You could put 2 or 3 of those bottles in and you woulnd't even notice.

 

[scott0987]

Re: Merc 5.0L V8 wont start

its carb, I was planning in just replacing the fuel water separator since its an inexpensive part and checking for water in the gas at the same time. As for it getting fuel, if there was no fuel flow, wouldn?t it just not fire at all when I try to start it?

 

[Don S]

Re: Merc 5.0L V8 wont start

As for it getting fuel, if there was no fuel flow, wouldn’t it just not fire at all when I try to start it?

Did you check inside the carb when pumping the throttle as I suggested?

Take the distributor cap of and check for moisture.

Could also just be flooded.

 

[scott0987]

Re: Merc 5.0L V8 wont start

No, i havent had a chance to check that yet, that will be either tonight or tomorrow nights project.

 

[scott0987]

Re: Merc 5.0L V8 wont start

i dont think its flooded, i tried it, let it sit overnight then tried again, ......still the same.

 

[Dryon]

Re: Merc 5.0L V8 wont start

Do as Don said.....check for moisture in Distributor cap and carb throttle pump. Also, check condition of spark plugs and confirm they are firing on every compression stroke. When was the last time they were replaced? Replacing fuel/water separator filter will not remove any water that may have made it past the filter into the Carb. May need to clean out carb.

 

[scott0987]

Re: Merc 5.0L V8 wont start

I am not sure when the last time there were replaced was, this is a new boat for me I just bought it back in June. I got it from a reputable used boat dealer that does a full inspection of all the boats it sells, I would assume they checked the plugs. But I can be 100% certain.

 

[Dryon]

Re: Merc 5.0L V8 wont start

If you didn't receive an itemized inspection list from the dealer, then don't assume they did any maintenance or replaced any parts/fluid. It would be best to assume that no maintenance has been performed since new. Dealer inspections are just that...inspection.

 

[scott0987]

Re: Merc 5.0L V8 wont start

A few new developments over the weekend, I pulled the fuel line out of the carb to test the pump, when you click the key to ? on ? nothing happens, but when you turn to start plenty of fuel is pumped, my new question is, is the fuel pump supposed to work both when the engine is turned to ? on ? and to ?start?. If I continue to hold the key to start, the engine runs fine, and I am able to rev it up and everything ( given I only did that for a few seconds as I don?t want to wreck the starter ) but then when you release the key and it pops back to ?on? it shuts down.

Any ideas?

 

[Don S]

Re: Merc 5.0L V8 wont start

So, your problem isn't that it won't start now, it's that it won't stay running.
That is probably the oil pressure switch that controls the fuel pump.
It is working properly by only working when the engine is cranking, but the power to the pump has to go thru an oil pressure switch to stay running.
It's a safety feature to keep the fuel pump from running if the the engine isn't running.

 

[scott0987]

Re: Merc 5.0L V8 wont start

so what is the fix for that??

 

[Don S]

Re: Merc 5.0L V8 wont start

so what is the fix for that??

That depends on what is wrong. It could be as simple as poor/corroded connections of the wiring, or the switch could be bad and you have to replace the switch.

 

[scott0987]

Re: Merc 5.0L V8 wont start

where is the switch located? and how much of a hassle is it to replace?