88 120 v4 at high rpm knock/clunk sound then dies

[zenchal26]

So Im working on a friends boat. He said the rpms wernt as high as they ues to be and its shutting down. after talking with him he said it was runnin around 6000 book says 4500-5500. So did compression test top two 130 bottom two 120psi, plugs looked good, cleaned carbs, put it in the water and ran it brought it up to wot for about a minute and it made a knock/clunk metal noise and boged out and died. Started right back up again went slow, punched it ran for 20 sec or so made same noise and died again. Started right back up drove it home slow. any ideas?

 

[Bosunsmate]

Re: 88 120 v4 at high rpm knock/clunk sound then dies

Check your gearbox oil and compression again
Have a look for any excessive unburnt oil on top of motor or lower leg

 

[Bosunsmate]

Re: 88 120 v4 at high rpm knock/clunk sound then dies

Check your plugs/piston for any impact damage too

 

[Faztbullet]

Re: 88 120 v4 at high rpm knock/clunk sound then dies

List of possible causes:Lower unit gears/bearing, upper crank bearing, broken skirt on piston and piece floating in crankcase.

 

[zenchal26]

Re: 88 120 v4 at high rpm knock/clunk sound then dies

ttt

 

[zenchal26]

Re: 88 120 v4 at high rpm knock/clunk sound then dies

ok so i took it out again and it died but no knock sound and would not start back up again. Now there is no spark on the starboard two cylinders. The top one sparks two or three times then quits and the bottom one is totaly dead.