I appreciate all the feedback, I basically posted right after the call where I was told it was my problem not his...after some deep breaths and some legal advice I've come to the conclusion, as did most of you here that it wasn't worth the fight...lesson learned...I fully admit mistakes were made on my part, that I relied on a reputation and took someone for his word and not in writing. I talked to two reputable shops, that specifically told me that they would offer little to no warrantee on non-stock marine engines, but if they had a case like mine they certainly would help me get to the bottom of what was wrong.
As far as the details, after about 8 hours it developed a knock, the builder heard it and we decided to pull the motor and look at it. The knock is severe at idle, up high at #5 cylinder, does not go away after the engine is warm, if you take a stethoscope to it, its up high, down at the skirt you hardly hear it...I don't think it's valve train related, we looked at the head, the valve seats all looked good. I'm think piston slap...but I have little experience in this...

I won't be pursuing anything from here, I'm taking the engine to one of the shops I mentioned to have them listen to it, and see what they think, and go from there...

And yes, I'll get everything in writing from here...

Sad but that is your best bet!

Vigilante justice is always an option ..

A question for the OP. Ontario, Canada is a big place. What part of Ontario are you and the original engine builder from ? Maybe some others that have had engines built by the same guy would chime in with their experiences, good or bad. I personally know a few builders in Eastern Ontario. Some good, some not so good.

I'm in south western Ontario, on Lake Huron...The builder was from the Port Dover area...

Just an update...I took the engine to probably the most highly recommended shop (where I should have went in the first place) in Ontario, especially as far as big blocks go. After examination they determined the block was way out of spec as far as the bore went. I had it bored out, new pistons, new connecting rods etc, I had the heads done, new adjustable rockers installed...

For the money I have into it I could have easily had a crate motor and some peace of mind.....but lesson learned...

Sadly I found a video of the original build being bench run by the original guy on his FB account...but was advised not to post or comment, as i could be accused of libel...

lol...you can't make this stuff up....

The water up here is thawing, I'm hoping to have everything back together shortly. I'll feel better when I hear a 502....with no knocks....

Whomever advised you not to mention his name because of libel is an idiot. Warm others for fu ck s sake so it doent happen to the next person.
Unless the whole thing is made up there`s absolutely no case for libel.

Yeah...he's gotta prove it's libel, you have the build sheets to prove otherwise.

I'm all for exposing lazy engine builders, but for most of the OSO stories, there's usually a 2nd perspective.

It sucks to put a lot of time and effort, money into a project and have it fail.

Sounds like there was too much piston to bore clearance?

How much?

Let's hear some numbers. How is the OP going to say there was a problem without the specs?

I'm curious how much the orig builder assisted the OP in getting the engine out of the boat and troubleshooting etc.

Why place the engine back in the boat without running on an engine stand? Or pulling the pan to check bearings etc.

How did the engine perform fornthe initial 8hrs?

Not calling out the OP here..., but there's more info required to paint the picture.

The 2nd shop is rebuilding heads etc. What was wrong with them from before?

As for libel, I don't think any action could be taken for just speaking about your experience. Just stick to the facts. But again, we're short of facts on the likely issue of piston to bore.

Does the builder have a machine shop? Did he get someone else to bore/hone? Or did he put hypereutectic pistons in a bore sized for forged and the piston to wall was 0.008"? Or was there a mistake in measurement?

Pics would also help.