odd puffing air sound from mercruiser 3.0 L

[cjones50]

so heres the deal guys. i've owned the boat, a 1994 bayliner with mercruiser 3.0 and alpha one, for about 3 months now and i've done a bunch of little work to make sure it keeps running well. but i'm getting a little suspicious of an odd noise that i hear at idle. the link below is not my boat but is exactly what it sounds like. the funny thing is the boat runns amazing once warmed up, never stalls, sputters, and at higher rpm the noise goes away. i can easily get 4600 to 5000 rpm out of it, and i hit 38 the other day which i hear is about right for my 19 footer. does anyone have any ideas if i should be worrying about it, and dig into the motor and pull the head to change the gasket? or do i just need to pop the valve cover off and lash the valves?

p.s-last weekend i pulled the exhaust/intake manifold and riser, and replaced the gasket. all freeze plugs and screw ins looked fine and didnt leak air or water.

thanks everyone

http://www.smugmug.com/gallery/9138137_M5rFJ

 

[jtybt]

Re: odd puffing air sound from mercruiser 3.0 L

Video didn't work for me.

 

[Apollo75]

Re: odd puffing air sound from mercruiser 3.0 L

That engine does not run well, I hope yours runs much better.

If all the other stuff on the engine is checked --- plug wiring in firing order etc.

Then:

I would do a compression check --- sounds like it is firing out the intake.

My guess is a bad head gasket leaking between two cylinders or stuck / bent valves.

Good luck

OFM

 

[cjones50]

Re: odd puffing air sound from mercruiser 3.0 L

thats what is so weird about it. it starts on the first turn of the key, you get it warmed up and it never has issues of sputtering or misfiring. i'm going to do a compression test and a blowby test this weekend. if i see good compression across all the cylinders, and not much blowby i'm not going to pay any attention to it. like i said, i easily can get 5000 rpm out of it so i know its firing on all cylinders, and it doesnt shake from the odd dip in rpm like i lost a cylinder. i just wanted to poke around here to see if anyone had a direct answer for me before i get totally worried about it. because right now its just annoying at idle.

 

[rspar]

Re: odd puffing air sound from mercruiser 3.0 L

I know it's not likely since you've been working on it but I kind of sounds like a loose spark plug to me. When the engine warms up it tightens.

 

[searay175snyder]

Re: odd puffing air sound from mercruiser 3.0 L

i had the same problem but i fine tuned my carb and added oil she had a lag also in my start but that went away with changing spark plugs and distributer cap

 

[Alpheus]

Re: odd puffing air sound from mercruiser 3.0 L

Don't go tearing anything apart just yet.

Perform a compression test and if you have a low cylinder perform a leak down test to find out where its leaking...

3.0 engines are not the quietest engines in the world...


http://www.youtube.com/watch?v=ofSiT...eature=related