1996 mercruiser 5.7 ticking no power

[19farmer]

Hey just joined cause I am at a complete loss on my motor I have replaced distributor cap, rotor, coil,plugs,wires, and carb,all filters it will crank up great idles great but when I try to plane underload it misfires and it's got a ticking noise like a exsaust manifold leak but when it starts laying over to go onto plane the ticking quites down and power picks up and runs smooth all day long it only does it under load with loud ticking untill plane any suggestions would be greatly appreciated thanks

 

[tpenfield]

:welcome: to iBoats . . .

What does 'laying over' mean :noidea:

If I were to paraphase what you described is that the engine misfires and has a ticking noise when you apply power to bring the boat up on plane. Once the boat gets up on plane the ticking goes away, and the engine seems to run fine.

Is that correct?

All the stuff that you replaced . . . at least you know that is not the problem

Got some YouTube video of the boat coming up on plane to share?

 

[19farmer]

Thanks for the welcome...yes the laying over means when it starts to plane the ticking quites down still ticks slightly but power seems to be fine will pick up and still run about 50-55mph it feels like it's down a cylinder untill rpms rise then it seem to pick up and run fairly decent never have left me stranded but it's not right

 

[19farmer]

It is very confusing on how the motor is acting it idles great and runs great on plane..I don't know if a head gasket would cause this problem or a valvetrain issue..thought if it has a wiped lobe on cam it wouldn't run great in any condition I haven't done much digging into internal problems thought maybe it was a ignition problem but I am afraid its something a little more serious gonna post a pic of one of the spark plugs I changed on the side that is ticking and see what you think happened....well I was but it want let me

 

[19farmer]

[No message]

 

[Bt Doctur]

unles your running surface gap plugs I dont see the electrode tip

 

[19farmer]

Yeah that's the problem it was burnt out or exploded out one of the two wondering if it ran lean and burnt valves or somtsomet to that nature

 

[Bt Doctur]

Severe detionation will also do it. you mention clicking under hard load

 

[19farmer]

Yes it a loud ticking wondering if I have a colasped lifter

 

[wrench 3]

Did you check the ignition timing?
An exhaust valve not opening properly from a wiped cam lobe or damaged rocker arm will cause a backfire through the carb. How does the inside of the flame arrester look?

 

[19farmer]

Yes I had the timing checked and set it will only cough a little through carb only when I come from idle straight to full throttle...the flame arrester was dirty black when I bought it but have cleaned it now scince I have owned it the boat and motor only has a little over 400hrs on it but don't think it was properly mantaned like it should have been

 

[Rick Stephens]

Ticking noise - my guess either detonation from running lean or a valve problem. You can always pull valve covers and measure lift to make sure you don't have a lobe gone or a lifter stuck. And if was mine, I'd be running it hard for a few minutes then flicking the ignition off and pulling all the plugs to see what they look like to rule out lean or a dead hole.

 

[achris]

Hello. Just joined because I am at a complete loss on my motor. I have replaced distributor cap, rotor, coil,plugs,wires, and carb, all filters. It will crank up great, idles great, but when I try to plane, under load it misfires and it's got a ticking noise like a exhaust manifold leak. Once it starts coming onto plane the ticking quitens down and power picks up and runs smooth all day long. It only does it under load with loud ticking until plane. Any suggestions would be greatly appreciated, thanks

I don't see 'compression test' in that list...

(also edited the above so it's more readable)

 

[wrench 3]

A compression test would be a good idea but a valve train problem may not show up on one.
It might also be a good idea to run some carbon cleaner through it, like this one https://www.iboats.com/shop/sierra-carbon-cleaner-12oz-18-9570-0.html and see if it improves any.
We'd have a better idea what we're dealing with if we could hear the noise.

 

[QBhoy]

If you were lucky, it might be an exhaust flapper gone. They make an alarming ticking noise at just above idle and up to around 1500-1600rpm (in my experience) and goes away after and further up the revs.

 

[Bondo]

Yeah that's the problem it was burnt out or exploded out one of the two wondering if it ran lean and burnt valves or somtsomet to that nature

Ayuh,.... Welcome Aboard,..... Sure sounds like a Severe case of Detonation to me,......

Advanced timin', or a lean condition are the 2 main causes,.....

Seein's ya had the timin' set, I'm guessin' that it's runnin' Lean,......

Btw,..... That noise is yer motor consumin' itself,.... it ain't just that electrode, but the piston, 'n valves too,....