2003 Mercuiser 350 MAG MPI noise

[Sea N Sun]

Hello

A few days ago my engine started making noise when it started; this noise has decreased a little now however when I took the boat out and was in gear will not go over 3000 rpm and the engine will vibrate a lot.
Since last time I had a mechanic look at the boat and he told me that may be a connecting rod or a wrist pin however to be sure he wants to take the drive out and check the engine again.
I have by now done compression test and all cylinders have 190 to 200 psi.
I clean the spark plugs and distributor cap, had the fuel/water filter changed, open the valve cover no water in the oil, no water in the cylinders and yesterday I took the boat out of the water and checked the drive oil no water or any metal there.
During the drive yesterday to take the boat out the noise was still there however the rpms increased over 3000 to 4000 and the boat increased speed no problem however I did not want to push the engine and I just did this for a minute or two.
I also listen to the engine with a stethoscope and the noise appears to come from the back port side. The engine only has 140 hours.

Any idea what the problem is?

 

[havasuboatman]

Re: 2003 Mercuiser 350 MAG MPI noise

Can you describe the noise? is it a knocking sound?

 

[Sea N Sun]

Re: 2003 Mercuiser 350 MAG MPI noise

Yes is a knocking noice which increases as the RPMs increase on the rear port side.

John

 

[Fun Times]

Re: 2003 Mercuiser 350 MAG MPI noise

You might want to think about carefully cutting open the oil filter to see if you see any kind of heavier metal stuck inside of it, As a starting point anyways.

There is someplaces out there that will do a test of the engine oil and help give you an idea of what is starting to go wrong with in the engine. Good luck to you with all of this.

 

[Sea N Sun]

Re: 2003 Mercuiser 350 MAG MPI noise

Hello

I took the engine out and I found that I had bend the cylinder #6 rod, everything was brand new within the engine. I checked the gasket and the block for cranks and I found nothing. It appears that the engine hydrolocked and bend the piston rod making to touch the crankshaft and make the noice. I check the exaust manifolds no leaks and there are also looking very good. Any ideas as to how water got into one of the cylinders causing it to hydrolock?

Thank
John

 

[zbnutcase]

Re: 2003 Mercuiser 350 MAG MPI noise

Broken or missing exhaust shutters would be my first guess. 'nutcase