Mercruiser 5.7 problem

[Mbelanger_63]

Hello, I have a problem with my Mercruiser 5.7 The boat is a holiday cruiser 26 ’, Mercruiser 5.7 engine with 4 barrel carbs. The boat was winterized and stored for 2 years. Before the launch I changed the gas filter and flushed the gas tank. When I put the boat in the water the engine runs well at idle and accelerates well to 20-22 knots and it comes out of the water normally. It cruises at 30-33 knots with no problem. After a few minutes it starts to lack torque, and loses speed. Then he refuses to pick up speed and begins pinging. The RPM doesn't go above 3200 and the banging noise gets louder until I lower the RPM to between 2500 and 2800 rpm. The engine runs well at low speed .... rebuilt 400 hrs ago

any idea ?
It was running great before storage.

 

[Rick Stephens]

Running lean. Good way to burn a piston.

Need to recheck filters and I would absolutely rebuild the carburetor. No way I am running it at all until I get it back in range for fear of burning it up. Also consider checking that you have 6-7 psi fuel pressure at the carburetor. Many things possible to make that number lower: plugged anti-syphon valve, plugged up tank vent, filter plugged with gunk, fuel pump, etc.

 

[achris]

... The boat was winterized and stored for 2 years. Before the launch I changed the gas filter and flushed the gas tank. ...

Sitting that long, you need to have pulled the carb, fuel pump and all the fuel lines out and stripped and cleaned all those too. I'd be suspecting vanish deposits in the carb, lines and pump. And what Rick says, if you keep running, the engine will run lean, and start blowing holes in pistons...

And after sitting for 2 years, I hope you changed the engine oil and filter and drive oil, serviced the drive water pump and greased unis, gimbal bearing and carried out all the other maintenances required.

Chris......

 

[Bondo]

Then he refuses to pick up speed and begins pinging.

Ayuh,...... Welcome Aboard,..... As noted above, it's goin' lean,.....

Don't run it like that, the pinging is the motor consuming itself,..... a hole in a piston will be the result,.....

 

[Mbelanger_63]

Thanks,
I will rebuilt the carb and Check the fuel pressure.
I’ll give you feed back when it’s done.

grease, oil, filter, are done
not the water pump.
should I service the water pump ?

thanks again?

 

[Bondo]

should I service the water pump ?

If it's been over 2 seasons, or ya don't know when it was done,.....

Absolutely,.....

 

[achris]

...should I service the water pump ?...

The thing that kills those impellers is NOT being used. Sitting unmoved for 2 years, it was dead after the first 12 months.

Chris.......

 

[Mbelanger_63]

Ok then,
empeller and gaskets
2-3 hours job ?
alpha 1 gen. 1

 

[achris]

Pull the whole drive and do everything. That's about a 2 hour job... If you don't do it very often, then allow up to 4. (I have videos on all that. 'My Videos' link at the bottom of my post signature)

Chris.....

 

[Mbelanger_63]

Which water pump kit do you recommend?
Alpha one gen 1

 

[achris]

Depends on how much you need to replace. It might be just the impeller, or it could be the whole pump (base included) needs to be replaced. You won't know that until you open it up...

Chris....

 

[Mbelanger_63]

Thanks , it files now !
i just rebuilt the carb.
now let’s do the water pump