mercruiser 4.3

[chapts]

Bought a used boat. Did not water test. Stupid me. But, put in the water. Engine started fine. Ran at idle speed for 5 minutes. Went to 1/2 throttle. good. Went to 3/4th throttle, heard a knocking sounds. Brought back to idle. Went back to a dock. Now, it knocks loud at any rpm. There was oil in the water (by the prop). Any ideas? Cracked engine? Mercruiser 4.3..

 

[Bt Doctur]

Is there oil in the engine? what was the engine temp? could be engine oil or drive oil or trim oil outside the boat

 

[henleyhale]

Sounds more like a head went south on you, start it up and determine which side the knock comes from then get out your compression test and see which cylinder losses compression. Then remove the head and inspect for a bent valve . Inspect cylinder for damage. You can leave the motor in the boat to do this, if it's just a head a trip to the machine shop is in order. As for oil in the water, is there water in your oil? Or was it uncombusted fuel being pushed out of an open exhaust valve? A head going out is generally following a lean condition, be prepared to track that down too.

 

[Bondo]

Ayuh,..... Welcome Aboard,..... Check the oil in the motor, 'n in the drive,.... they both turn together,....

Only the prop shaft, shifts,....

 

[chapts]

There was oil in the engine. The oil level was over the high mark. The oil seemed thin. Almost like power steering fluid....maybe that was fuel as mentioned. Any maybe that was why the oil level was high. I did not smell it... The temp really did not go up at all when running the boat. Ran it for 10 minutes. Thanks for the replies

 

[chapts]

Took a smell of the oil and it smells like fuel. What you the general cost be to get something like this repaired?

 

[UncleWillie]

What year is boat?

Fuel in the oil is likely a ruptured rubber diaphragm in the fuel pump. Cheap fix!
The thinned out oil will cause all the noise and leak past the rings. Check the spark plugs.
Your 25w oil is now 0.25w.

Be prepared to change the oil and filter twice.
Put in some inexpensive 40W oil to soak up what remains of the gas after you drain it.
Change it again after getting it up to operating temperature. ~10 minutes.
Then refill with the pricey Quicksilver oil.

 

[NHGuy]

Yah, you probly dodged the bullet. With boats you can't use a car fuel pump. The marine pumps contains provisions to keep fuel out of the bilge which is a fire hazard. Car pumps don't concern with that so no car pump.
Also you can put a bolt through the hole in the front of the motor to hold the pump pushrod in place while swapping the pump out. If you do that it will save some time and effort.

 

[chapts]

The year of the boat is 2000. I will change out the fuel pump, change the oil and see what happens. Thanks for all the input.

 

[Bondo]

The year of the boat is 2000. I will change out the fuel pump, change the oil and see what happens. Thanks for all the input.

Ayuh,..... You have an electric fuel pump,..... It Ain't that,.....

How much over full is the oil level,..??

 

[chapts]

it is about an inch and a half over the full line. Smells like fuel and it is very thin