Mercruiser 3.0 shifting makes bad noise like a bang

[shouan]

I have a bayler with 3.0 mercruiser engine, when I want to shift forward or rear I hear a bang sound just once and then it starts running,
I am offraid something in gearbox is going to be damaged.
Also sometimes when I want to shift forward or rear the engine turns off and I need to start it again, but if I shift all the way down (max speed) immidiately instead of accelerating slowly it is fine.
Please help.

 

[Don S]

Re: Mercruiser 3.0 shifting makes bad noise like a bang

Sounds like you have a couple of issues, the bang is probably the idle set to high on the engine. Should br 750 rpm MAX!!!
It dying sounds a lot like the lower shift cable failing causing a binding and holding the shift interrupt switch engaged too long.
Have a read of this thread. http://forums.iboats.com/showthread.php?p=1930449#post1930449


It would also be handy to add some engine and drive info. 3.0L engines have been used since the early 70's and there are all kinds of changes over the years. Serial numbers are your best bet.

 

[fishrdan]

Re: Mercruiser 3.0 shifting makes bad noise like a bang

if I shift all the way down (max speed) immidiately instead of accelerating slowly it is fine.

You need to shift into gear swiftly, so the gears mesh quickly. Take note of where the shifter is positioned while in forward gear and the engine idling, you need to move the shifter quickly into that position. Same for reverse. It takes a bit of practice, but once you get the hang of it you will "pop" it into gear with the boat still idling. Out of the water, the drive will make a loud "thunk" as it goes into gear, but it shouldn't be loud on the water.

Take Don S's advice on the idle RPM and possibly having a bad lower shift cable.

 

[shouan]

Re: Mercruiser 3.0 shifting makes bad noise like a bang

Thank you Don
Can you please help me and tel me how to check and fix the lower cable?
also is there a possibility that the gear box is running out of oil? or it has water mixed ? (there is no sign of oil leaking though)
How can I change the gear box oil just in case?

Best Regards,
Shawn

 

[shouan]

Re: Mercruiser 3.0 shifting makes bad noise like a bang

Thank you Fishrdan,
Tha problem I have is when I want to run the boat in low speed the engine vibrates and it turns off. and I need to star it over, but if I run fast or full speed I do not have this problem at all. (the boat is using carbrator as fuling system)

Best Regards,
Shawn

 

[Don S]

Re: Mercruiser 3.0 shifting makes bad noise like a bang

It would also be handy to add some engine and drive info. 3.0L engines have been used since the early 70's and there are all kinds of changes over the years. Serial numbers are your best bet.

You still haven't posted any ID info for your engine and drive.
There is all kinds of info available, we just need to know what exactly we are working on.

 

[Searayb]

Re: Mercruiser 3.0 shifting makes bad noise like a bang

I learn something new every time I visit thisn site. Thanks Don

 

[fishrdan]

Re: Mercruiser 3.0 shifting makes bad noise like a bang

Tha problem I have is when I want to run the boat in low speed the engine vibrates and it turns off.

Sounds like you have tune-up issues. Post up your engine S/N so Don S can help out with some doc's and such, he's the guru here. (His crystal ball is cracked, so he can't conjur up what your engine S/N is )

 

[Bondo]

Re: Mercruiser 3.0 shifting makes bad noise like a bang

Thank you Fishrdan,
Tha problem I have is when I want to run the boat in low speed the engine vibrates and it turns off. and I need to star it over, but if I run fast or full speed I do not have this problem at all. (the boat is using carbrator as fuling system)

Best Regards,
Shawn

Ayuh,... Sounds like the carb needs a rebuild, or replacement...

 

[shouan]

Re: Mercruiser 3.0 shifting makes bad noise like a bang

Thnak you all for your helps
here is the engine Serial Number: 0L365936
Transom S/N: 0L549244
Drive S/N: 0L448589

 

[fishrdan]

Re: Mercruiser 3.0 shifting makes bad noise like a bang

Ayuh,... Sounds like the carb needs a rebuild, or replacement...

Could just need some adjusting to the idle mixture screw(s). I'd try that before rebuilding the carb,,, which is likely needing to be done.

Before touching the idle mixture screw, mark it's orientation and then turn it all the way in (lightly seating it) so you know where it was originally set. IE; slot lined up at 45* and 1 1/3 turns to seat it. If you need to rebuild the carb, you have it's initial idle adjustments and can tune it from there. I wrote this down in my service manual, has come in handy when I've serviced the carb.

 

[shouan]

Re: Mercruiser 3.0 shifting makes bad noise like a bang

Thank you

 

[shouan]

Re: Mercruiser 3.0 shifting makes bad noise like a bang

Can you please tel me how to buy a carb rebuilt kit? is there any model number I should use?
and also how to buy a lowe shift cable if its needed?

Thank you

 

[shouan]

Re: Mercruiser 3.0 shifting makes bad noise like a bang

Can you please tel me how to buy a carb rebuilt kit? is there any model number I should use?
and also how to buy a lowe shift cable if its needed?

Thank you

 

[Bondo]

Re: Mercruiser 3.0 shifting makes bad noise like a bang

Can you please tel me how to buy a carb rebuilt kit? is there any model number I should use?
and also how to buy a lowe shift cable if its needed?

Thank you

Ayuh,... Take yer Serial numbers, 'n year, 'n model,...
Go to the iboats marine store, 'n follow the prompts...

 

[mark1905]

Re: Mercruiser 3.0 shifting makes bad noise like a bang

Not to be pessimistic, but it sounds like your best investment in this case may be a good marine mechanic so that you don't end up making things worse and/or throwing money at things that you don't need to.

 

[fishrdan]

Re: Mercruiser 3.0 shifting makes bad noise like a bang

You are going to need a service manual before buying any parts, see if one of the guys can post up a link for you. The carb rebuild is pretty straight forward, but you have to be meticulous about cleaning the parts and putting it back together, then comes the tuning of the carb... The lower shift cable isn't the easiest thing to replace, it requires the drive to be removed, then you have to make precise adjustments or the drive won't shift properly. If you have the skills and patience to follow the manual "to the T" you could do it, but this work isn't like an oil change or swappin' out some spark plugs.

I'd start with the carb work and see how it does from there.