Motor Knock

[mikezxx]

I have a Marina doing a repower to my 28' Regal. They built out the new motor on the floor before installing and ran it about 20 minutes and it ran fine. After the install when water testing They ran the boat another half hour. The motor ran fine but the boat was leaking. This boat also has a new outdrive with all new bellows and gimble bearing. They removed the motor and outdrive and found that the transom assembly was bad with corrosion and a few broken bolts. They then installed a new transom assembly and while reinstalling the motor they dropped it damaging a large part of a stringer that the motor sits on that they actually tried to hide from me. Also broke one pully, and bent another one one the motor.

Now that they have the boat back together and running the motor makes a random knocking noise. It's not a constant knock and doesn't change at any rpm just a random knock every few minutes. This motor is brand new and successfully ran twice with no problems, and now makes this knock noise after being dropped and dropped hard enough to do physical damage to both the boat and motor.

What could be wrong with the motor, and what are your thoughts knowing it ran fine twice before being dropped that the damage to the motor is a result of being dropped?

Any and all your thoughts would be greatly appreciated. I've spent close to 20k one this project, and this mess is making me sick. I need to know what my next step will be when I approach the owner of the marina that's been working on it. Also, they've had the boat for well over a year maybe closer to two years.

Thanks for any and all of your help.

 

[alldodge]

A random noise (knock) would be hard for anyone not listening on the boat to be able to advise. Could be anything, something loose in the bilge to something on the motor. Could be the hull

How was the stringer fixed? Look where it was repaired to see if something is starting to show

With the transom assembly having broken bolts, this would have me look at the transom to see if its getting soft. Have not heard of bolts breaking from an installed assembly without some kind of accident/impact.

I would go back to the Marina and see what they say

 

[mikezxx]

A random noise (knock) would be hard for anyone not listening on the boat to be able to advise. Could be anything, something loose in the bilge to something on the motor. Could be the hull

How was the stringer fixed? Look where it was repaired to see if something is starting to show

With the transom assembly having broken bolts, this would have me look at the transom to see if its getting soft. Have not heard of bolts breaking from an installed assembly without some kind of accident/impact.

I would go back to the Marina and see what they say

The Transom it's self is solid. The boat was dropped and the lower outdrive cracked. I believe this is how the bolts broke, and there was significant corrosion where they broke. The stringer was not fixed. They were going to let it go I guess hoping I didn't notice.

 

[Paintman1960]

Shady business practice right there !!

 

[Lou C]

I would not be happy with these people at all. If the engine knocks and pulleys were bent it makes you wonder if they bent the crankshaft. Not repairing the stringer? I would NOT have paid the balance if the bill till both were rectified!

 

[nola mike]

I would not be happy with these people at all. If the engine knocks and pulleys were bent it makes you wonder if they bent the crankshaft. Not repairing the stringer? I would NOT have paid the balance if the bill till both were rectified!

Yeah, I'd be concerned about the crank, maybe bearings if it dropped that hard. I'd at least demand an extended engine warranty for a year or 2

 

[mikezxx]

It's been a year and a half and I'm already into it for 20k. I just want the thing fixed and running. I'm waiting for a call from the head mechanic now and will update the post as to where we're at now.

 

[crazy charlie]

So rather than speculate and drive yourself nuts ,do this and isolate the noise yourself .Get a wooden broom stick.Put one end of the stick on the exhaust tube directly behind the risers with engine running.Put the other end of the broom stick in your ear.YES CORRECT,in your ear.You now have a functioning extremely effective stethoscope.I think you will hear your "knock" here.If so dont panic.It is an exhaust flapper and easily fixed or just leave it alone,not a big deal.If this is not the source of the sound,then put the stick where you think the sound is coming from.When you find the correct spot you will hear it loud and clear .I hope it is an exhaust flapper.Post back.Charlie

 

[mikezxx]

Thanks Charlie,
There taking the motor out now . It has to come out to fix the stringer anyway. They want to strip it back to the long block and have me bring it back to the marina that built it and go from there. I did ask that we run it again on the floor before they strip it as it will be isolated from the boat. So I'm hoping Monday we can do that. I'll keep you posted.

 

[ThetaChi12]

So rather than speculate and drive yourself nuts ,do this and isolate the noise yourself .Get a wooden broom stick.Put one end of the stick on the exhaust tube directly behind the risers with engine running.Put the other end of the broom stick in your ear.YES CORRECT,in your ear.You now have a functioning extremely effective stethoscope.I think you will hear your "knock" here.If so dont panic.It is an exhaust flapper and easily fixed or just leave it alone,not a big deal.If this is not the source of the sound,then put the stick where you think the sound is coming from.When you find the correct spot you will hear it loud and clear .I hope it is an exhaust flapper.Post back.Charlie

I had a sporadic, non rhythmic clatter a while back that I was concerned was engine knock. After some investigation, I found a bad water shutter to be the culprit.

 

[Lou C]

An engine stethescope really helps with these kinds of problems. I had a similar issue when I did my top end overhaul (reman heads) 4 years ago. Heard a knocking noise that was intermittent. At the same time I had replaced the exhaust system, changing from the older OMC one piece V6 exhaust to the newer 2 piece exhaust. These newer style units have larger water ports and flow more water. One of the flappers was making noise, only at certain times. Drove me nuts trying to find it.

old exhaust notice small water ports....
New exhaust used on later OMCs and Volvos...notice bigger ports.
so it could be something as simple as that. Any wobble in the crank shaft pulley?

 

[tank1949]

The Transom it's self is solid. The boat was dropped and the lower outdrive cracked. I believe this is how the bolts broke, and there was significant corrosion where they broke. The stringer was not fixed. They were going to let it go I guess hoping I didn't notice.

U sure transom is not rotten???? Who dropped it? How old is boat? Wood or synthetic transom core? Why didn't mechanics examine or call u to examine damaged transom assembly(s) and CORROSION? If stringer damaged, perhaps alignment is out as well??? Sounds like a salt water stored boat due t corrosion. If so, I suspect you may have to pull and rebuild all metal and wood. Been there!!!!!