What can be done about knocking on a 1989 Renken Seamaster fishing boat w/ mercruiser 4.3 v-6?

Question

1989 Renken Seamaster fishing boat - mercruiser 4.3 v-6 - I had about $2,000 worth of work done to it, wires, gimbal bearing, ... I would have to pull the extensive invoice to list all of the parts, it included pulling the engine and out-drive off of the boat. The first time out the boat was run for about an hour when I discovered oil everywhere, the oil filter had a hairline crack and had been spaying oil everywhere and emptying the oil reserve. The mechanic said was now have either an "engine knock" or "rod knock". I was so discouraged that I tarped the boat and left it (I did winterize it and stabilize the gas). I see now there are a lot of companies offering remanufactured engines but I just don't know what I should do next. I really do not want to spend $3k to have a new engine installed... I don't know what is really wrong with the boat, what does running on low oil/pressure do? is this a knock scenario? Any thoughts, opinions, direction at all would be much appreciated. Steve

Answer 1

I hate to hear this. It probably what the mechanic says. The Crankshaft has holes to oil the main bearings and rod bearings. It Possible a bearing damaged and the rod is knocking.
Did the mechanic listen to the engine run and knock?
It is a knock and not a fast tapping sound?
A weak tapping may be a Hydraulic Lifter, but, the heavy thump/knock is most likely a bearing.
I sorry and really not know what be the best thing to do. You may find a used boat that run good cheaper than a new/rebuilt engine and swap it out. Then you have some extra lower unit parts if you ever need or sell the lower unit off the other boat and recoup some of your money. A 1989 you may get lucky and find one cheap. Many may not have a lot of hours on them, but, check the oil for white and look around on the outside of the block for rust cracks that look like water run from it, if the block have a crack this be the way to see. Or, your only other option is someone open the engine and fix the knock. May have to "Turn" the Crankshaft too if it damaged. :-(