92 351 has major knock

When I took my 92 SNOB 351 out of storage last week it had a loud knock/tick coming from the driver's side of the engine. The boat shop looked at it and then I took it to an old time mechanic shop that knows engines. In 2014 I had the original block replaced with a Jasper block due to a crack in the block. 3 seasons and 110 hours later now I have a really bad knock. The machine shop repair place upon my approval took a chance and I had all the lifters replaced. It didn't resolve the knock. Short of pulling the motor and dropping the pan it appears that we will end up running it this Summer until it dies. The oil pressure is great 60+ lbs and the compression is good all around except for the #2 cylinder which is a littler lower but not a big issue.

The boat is stored in the underground caves here in KC where it doesn't get below 60 degrees all winter. It's got me totally baffled as to the cause, the knock wasn't there at the end of the season when we put it on the trailer.

The boat shop is suggesting I just replace the whole motor with a new PCM crate motor - 5.7l with EFI etc.

Any suggestions?

Anyone know about someone who has put a new GM/PCM engine in a 92 Nautique OB?

ibiz wrote: The machine shop repair place upon my approval took a chance and I had all the lifters replaced. It didn't resolve the knock.

ibiz wrote: When I took my 92 SNOB 351 out of storage last week it had a loud knock/tick coming from the driver's side of the engine. The boat shop looked at it and then I took it to an old time mechanic shop that knows engines. In 2014 I had the original block replaced with a Jasper block due to a crack in the block. 3 seasons and 110 hours later now I have a really bad knock. The machine shop repair place upon my approval took a chance and I had all the lifters replaced. It didn't resolve the knock. Short of pulling the motor and dropping the pan it appears that we will end up running it this Summer until it dies. The oil pressure is great 60+ lbs and the compression is good all around except for the #2 cylinder which is a littler lower but not a big issue. The boat is stored in the underground caves here in KC where it doesn't get below 60 degrees all winter. It's got me totally baffled as to the cause, the knock wasn't there at the end of the season when we put it on the trailer. The boat shop is suggesting I just replace the whole motor with a new PCM crate motor - 5.7l with EFI etc. Any suggestions? Anyone know about someone who has put a new GM/PCM engine in a 92 Nautique OB?

Having no idea what your knock/tick sounds like, I'll ask the silly question, is there any chance it's external to the engine?

A loud knock and a tick wouldn't exactly sound alike.

A short video would be real helpful to people.

Your raw water pump is on the right side and if it has a bad bearing you can get some funny noises from that. You could remove the belt and start the engine long enough to see if the sound is still there. Could be a long shot but won't take long to find out if it's the pump

Duane,

Thanks for the suggestion. I will likely give that a try.

Have you checked for cracks or leaks where your exhaust manifolds bolt to the block? They can produce a sound just like a lifter tick/knock.

Pouring some marvel mystery oil down running carb can knock carbon loose too.

Ibiz we need a video with you moving around the engine.

stuck or collapsed hydraulic lifter sounds rational.

Did u run it on the hose before taking it out this season? Remote chance you turned off the engine before shutting off the fake a lake? Could possibly have hydrolocked a cylinder and bent a connecting rod.

Maybe drop pan (ugh) and look for main or rod bearing material.

I'm sorry I'm. It much help without audio. You can learn a lot from
Sound (where from, 1/2 crank speed or crank speed).

Get us all a video so we can guessculate.

With your engine running ( and Knocking ) remove one spark plug wire at a time on the noisy bank. If this makes no change in your noise it is in the overhead, Cam, Lifters and valves. If the noise gets quieter with the guilty plug wire pulled off you can isolate to that cylinder. It will be related to the Piston, Connecting rod or Main bearing under that cylinder.   Carbon deposits can make a piston rock hard in a cylinder and create a sound similar to a lifter tap. A rod knock is lower in the block and louder, same for a main bearing.
I have heard of Fuel Pumps causing loud knocks when they go out also so rule that out.
For $15.00 you can buy a mechanics stethoscope at the local parts store and isolate your noise location.

If water got in that cylinder it could bend a rod and cause the piston to make noise.

Jasper Engines is a very reputable house. You can call them tell them all details and they will help diagnose also. They may even stand behind the engine or at least partially stand behind it since it is most likely out of warranty.
They do good work and use good parts so you chose a good engine.

I will take a look at the troubleshooting tips you suggested.

But both the Boat shop that bought the engine from Jasper and installed it and the automotive shop that does a lot of work with Jasper got no where with the Marine rep.

They were told it's a two year warranty period! They wouldn't budge and provider any reimbursement for parts or labor.

ibiz wrote: The engine was run on the trailer to pull in 3 gallons of anti freeze at the end of the season. Engine was shut off as soon as it got to the bottom of the antifreeze in the bucket. ..

Did you drain ALL the water out of the system first?

Yes. all the water was drained out of the engine first and then it was run with the antifreeze.

But also note here in Kansas we have underground caves in the area so it was stored in a constant 65 degree environment all winter - no chance of freezing.

Sorry you are having problems Jerry! While I am no expert, and you got some excellent advice here, I will say that I have spun a few bearings before and that noise does NOT sound like a knock/noise from that. Not as loud or consistent.
Good luck with it. Please keep us posted.

Yes we have checked for leaks.

Jerry

Here's a video from last year in the linked thread just for reference You can compare noises

ticking noise

Edit seem to have to click a couple of times on the start symbol to get sound.

I didn't try the water/steam trick yet. I wanted to upload the video/audio and get more feedback before I tried that.

Do you think the water/steam approach is the same as pouring some marvel mystery oil down the carbs? It seems to be similar from what i have read online?