Mercruiser 470 - Bad bearings or top end? See video

[nicolajjr]

Hi Guys

A friend in the habour has this Picton Boat with this engine, yesterday he went full throttle and suddenly the knocking noise came. He shut of the engine and got a tow in.

Check the video: https://www.youtube.com/watch?v=EU_m2Fsl3vs

My ears say the knocking is from the top, but what do you guys say? Is it crank bearings?

have a nice evening.

 

[2fishy4u]

Ouch, sounds exactly like mine did beginning of the year....... I ended up with a complete rebuild.

 

[Bt Doctur]

was the engine oil at the correct level? before and after . Remove the valve cover, maybe just a bent/busted pushrod or rocker

 

[Bondo]

Ayuh,.... Sounds like it's got alot more problems, then just the knock,.....

 

[harleyman1975]

Sounds like bottom end.

 

[stonyloam]

Hmmmmm can you feel it if you put your hand on the valve cover? If not and if it sounds like it is coming from the top, it might be that the thermistor plug in the back of the head has rusted out and you are hearing the exhaust from #4 blowing out. If you think it might be, put your hand behind the head and you will feel the exhaust blowing out. Just a guess.

 

[nicolajjr]

No Title

Hi Guys.... Yes its needing a rebuild... a big one. Just checked the compression today, 50-60 PSI on all 4 cylinders...

I think the only way to do this is:

Rebuild Top end
New Pistons
New Gaskets
New Oil Pump
New Rod bearings 0.30

 

[Bondo]

I think the only way to do this is:

Rebuild Top end
New Pistons
New Gaskets
New Oil Pump
New Rod bearings 0.30

Ayuh,.... You need to go Machine Shop shoppin',.....
Find yerself a Machinist yer comfortable with, 'n have 'im assemble atleast the long block,....
He can tear it down, 'n mic it up to see what needs machinin', 'n what can run again,....
Until then, there ain't no Plan,....

If ya wanta Diy it, pull it, 'n strip it to the Long Block, 'n haul it to the Machine Shop,....
When it's done, re-dress it, 'n stuff it back into the boat,.....

Rebuildin' a 470 ain't a Diy kinda project,...
Unless yer already a Machinist,......