Marine Forum

engine 3.0 volvo penta knocking

chaz01

01 January 2007 04:41:03

Joined: 01 January 2007 04:36:20 | Posts: 1

My 2001 Stingray LX180 with a Volvo 3.0 SX is having problems. I was testing various props and found a stainless steel (14 x 19) one that worked well. After a 2 hour excursion on the water the motor started to make an unusually sounds before it left me stranded on the water, thank goodness for that membership with Sea Tow that I never thought I would ever use. They saved my skins. Eventually I disassembled the top of the motor hoping it was a blown head gasket. I took the head to a machine shop who informed me that the head showed signs of water in the 4th cylinder. They returned it after a thorough clean up where after I replaced all the necessary gaskets and did a compression check on the engine which all registered 150 psi or above on all the cylinders. The boat only had a total of 75 hours on it. Wanting to rule out the possibility of a bad riser and manifold I replaced both of them. I started the engine and quickly realized that knock was still noticeable further more the engine would almost back fire when I attempted to raise the rpm level, not to mention the fact that I will not idle.
I believe it is a rod knock. Need to ask if any of you smart guys know of any other possibilities, before I tear the entire engine a part.