Mercruiser 3.0 knock video

mb7

Seaman Apprentice
Joined
Mar 11, 2009
Messages
30
Everything starter with a bad manifold and riser
but the hole was very small so I could start and run for 20 minutes and them start to run rough and died.That was when the knock started

Sounds like it is from the bottom

Please guys help to figure this out what is making it

Here is the link

http://www.youtube.com/watch?v=X4IChzYrd80

Now with the new riser the engine runs great (very quiet knock),until ,warms up and gets a louder knock and runs rough and dies, but starts right up.

thanks
 

mb7

Seaman Apprentice
Joined
Mar 11, 2009
Messages
30
Re: Mercruiser 3.0 knock video

I am thinking to open up this weekend!!!!
 

Blk-n-Blu

Master Chief Petty Officer
Joined
May 12, 2004
Messages
821
Re: Mercruiser 3.0 knock video

Since you still can run the motor, you might want to do a Compression test before pulling anything apart, IMHO
 

mb7

Seaman Apprentice
Joined
Mar 11, 2009
Messages
30
Re: Mercruiser 3.0 knock video

Thanks for the reply

I did yesterday

137 150 150 141

Are these any good?
 

mb7

Seaman Apprentice
Joined
Mar 11, 2009
Messages
30
Re: Mercruiser 3.0 knock video

I open the engine ...

Two pistons ears (3 and 4) were broken

I couldn't find any play on the bearings, but they have some wear
marks

The Crankshaft and the pistons walls looks shine
with no scores

This is my first engine rebuild

Please help

What should I check?

thanks
 

mb7

Seaman Apprentice
Joined
Mar 11, 2009
Messages
30
Re: Mercruiser 3.0 knock video

The bearings from the piston rods has this numbers:

A GMM 400

545369

86 B4 1

I think they are the original ones...
 

atomb

Petty Officer 1st Class
Joined
May 1, 2009
Messages
335
Re: Mercruiser 3.0 knock video

two pistons ears are broke you might have to educate me piston ears? Im thinking you might have found your issue? Anything thats broke having to do with the pistons needs to be replaced for sure. Did you pull engine out or just yank the cylinder head off?
 

Jessfly1

Seaman Apprentice
Joined
Jul 5, 2009
Messages
36
Re: Mercruiser 3.0 knock video

Im thinking by "ears" you mean the piston skirt. This is not good! The whole thing needs to be rebuilt if thats the case. If you do rebuild it you need all new bearings main, rod, and cam. Pistons (since one is already broken), you need to check your crank and bore (a machine shop can do this) While your at it you should drop off the head to get that checked. I would consider changing the cam and lifter if they look worn (always change as a set!) this is also where you can go aftermarket and add possible horse power. Replace freeze plugs. Replace all gaskets and minor things like plugs, rotor, cap, oil pump, etc... Invest in a good shop manual and do your homework. Its not that hard to do a rebuild just take your time and pay attention to detail! You have your work cut out for you....Good luck.
 

6meter

Chief Petty Officer
Joined
May 15, 2010
Messages
525
Re: Mercruiser 3.0 knock video

Wondering here, were you running the motor without muffs on and the outdrive attatched?
Broken piston skirts will cause a piston slap. Noisey. The cylinder walls were ok with the bad pistons?
As in any job, there is a right way or the cheap way. Not saying the cheap way will last though. Biggest bucks, you send it to a machine shop. It is only a 4 cyl so it won't be that bad. Or a DIY with new pistons, rings, main and rod bearings with proper clearances, marine gaskets, cyls honed etc and head redone, guessing $1000 or less along with a friend that knows. HTH
 

mb7

Seaman Apprentice
Joined
Mar 11, 2009
Messages
30
Re: Mercruiser 3.0 knock video

The engine had the timing (i think) 180 d off so was igniting when the intake valves was open. (loud noise from carb)
The pistons wall, looks perfect, no scratches at all. I think if I just re hone. Doing that, should I use the same size rings?

The Crank Shaft had no scores and are all shine with no marks

The engine always run with with water, never overheated.

Thanks for the response...
 

Joshua Nichols

Lieutenant
Joined
Jun 29, 2009
Messages
1,431
Re: Mercruiser 3.0 knock video

Great video... Thought it was going to pop right there.. Kinda sounded like a diesel... Poor little engine.. I never heard of piston ears.. I think the pistons for that engine are rather expensive.. Mic the cylinders and see if they are within spec..
 

Joshua Nichols

Lieutenant
Joined
Jun 29, 2009
Messages
1,431
Re: Mercruiser 3.0 knock video

Yeah it is.. Thought I saw on here here this fella said they was a 100 bucks a lick... But that is cheap enough
 
Top