Rod Knock, anything else to check before pulling engine?

[Sattech200]

Good afternoon everyone!

Just bought an 87 Rinker 25' with a GM 350/OMC outdrive.

Previous owner had engine rebuilt two years ago. One of the first trips out this year and a rod started knocking. I don't beleive there's even 25hrs on the rebuild.

Im an experienced engine rebuilder and yes, it does sound like a rod knock from the 20-30 seconds I heard it running. But something seems kind of strange considering it was just rebuilt. I'm wondering if there might be anything else, like the u-joints maybe or a tooth on one of the gears in the outdrive, that might cause a similar noise to a rod knock? That I should check before pulling the engine.


I appreciate any input!

 

[alldodge]

If its knocking its more then likely a rod. Some rebuild motors and don't have the expertise to do it right, and some do

Can pull the drive and fire it up to see if it still has the knock is about the only other thing to try

 

[Sattech200]

Ok, sounds good, I appreciate it. I'm expecting probably a crank kit.

 

[Scott Danforth]

Ok, sounds good, I appreciate it. I'm expecting probably a crank kit.

I would suggest a proper teardown before you buy parts. The last motor I rebuilt that had a rod knock had 4 spun bearings and needed align honing the mains and decking prior to boring/honing and replacing the entire rotating assembly

 

[Sattech200]

I absolutely agree!

Got engine out last night and pulled oil pan. Quick recap we just purchased this boat with a susoected 'rod knock'

I have ran the engine twice for 15-20 seconds and it clearly sounded like a rod knock. The second run was with the outdrive removed but found that made no change.

As I was removing the starter wiring I noticed a jasper label on the block. I thought to myself Hmmm, just wonder if possibly any warranty. A quick check online didn't mention about transferring owners so I called jasper, great guy I talked to by the way!, and he indicated the warranty follows the engine. I was like COOL! He was able to check the numbers and unfortunately it was installed in May of 2017 so unfortunately I didn't get lucky. So anyways, at least I know it's a fairley fresh reman and not somebody that just threw a set of rings and oil pump into it.

When I went to drain the oil I found 3-4 quarts of water in the oil. I wish I would have checked that before pulling the engine, doh oh well.

I specifically noticed probably 90% of the water was NOT emulsified with the oil. The water drained out first then oil followed.

I managed to get the engine flipped and pulled the oil pan off. I did a quick tap of each rod and did not find any movement on the rods. At that point I was done for the day.

Figure I need to still pull the rod caps off for a visual to see what the status is and probably the mains also since I'm there.

I did notice when rotating the crank that it would like to bind in a certain spot.

My big concern/delima/decision is where the water came from? I'm reading about this phenomenon with backwash occuring? I didn't inspect my flappers when I pulled the engine. Or maybe exhaust manifolds? (Had that happen on an onan generator once) I looked closely at exterior of block and didn't see any cracks visually.

And trying to decide if it's worth saving this engine or if I should just look for a replacement.

 

[alldodge]

With almost a gallon of water, I would start looking for improper winterization and there is a crack somewhere

 

[vasy]

Call the rebuilder and see if they will offer you discount on a new block.
You have some time now over the winter to throw in a new one.