gt40 knocking

[bobchris]

you have piston issue and it's slapping the cylinder wall because it sharnk and created more clearance, Saw this on another GT40 engine couple years back seems it was a common problem that slide under the radar. They guy actually got PCM to throw in on a new motor.

not very common for the wrist pin to go before some other bottom end pieces fails.

[bobchris]

about the only other issue it could be would be carbon build up on the tops of the pistons and on the valves. So if you run a can of seafoam through the induction system you might get lucky.

[g33b0]

ok.......here is the question.......from what yall are saying is wrong....................new engine or not........worth fixing or not..............better deal to gett new engine or to fix.........is it fixable.......worth fixing..............how many parts will be damaged with whats going on...........can i do the service myself or will i need special assistance.........how much will it cost if i do it myself,...how much will it cost if i have some one else do the work........i need to know ..........did i get screwed or not

[2gofaster]

That noise hasn't been covered up by anything over the last two years. So best guess is that the previous owner didn't know there was something wrong, or there wasn't anything wrong then. If you have to ask if you can fix it yourself, then the anwer is no. If you're mechanically inclined, pulling the engine isn't hard if you can find a way to hoist it out of there.

[2gofaster]

You're in Andrews. If you can get the engine out, you can take it to Roberts Machine in Midland. Ask for Pete. (432) 683-4301 He's the best in your area and did machine work for me on my turbocharged 1600 horsepower small block ford in my race car.

[Cibolasam]

I have a 97 Sport with the GT-40. A few years back I had a knock in my engine also. It ended up being a scored cylinder wall. There was something fishy about this problem so I did some research and found a few boats had the same problem.. To make a long story short CC paid for all the parts and I had to pay the labor, but from what I understood the computer leans out the engine too much at high ambient temperatures and causes this problem. Hope this helps.

[g33b0]

ok took to mechanic....they wouldnt even bother with engine noise because they said i had multiple exhaust leaks.......from manifolds to the muffler...........so i epoxied the muffler......i dont think leaking anymore.............bought two new exhaust manifolds with service kit ( gaskets, bolts}........so i am hoping my knock is from the exhaust leaks...............fyi the only reason i am buying new manifolds is when i tried to put new gaskets in i was tightening the bolts and when i was loosening one off...........one bolt broke off and the other wouldnt tighten...................28lbs of torque, right!?................so **** i figured i would go ahead and replace ten year old manifolds......

[g33b0]

ok another thing just came to mind......i am new to boating and new to nautiques and i am learning learning learning everyday..................everyone asked if the knock was happening before i winterized and if i had heard it before............now i am remembering last year when we took the boat out ............that the exhaust was producing plumes and plumes of white steam/smoke................and i never thought anything of it because we were wakeboarding with a dang wetsuit on......the water was like 50 to 60 degrees..................but what if the water wasnt causing the steam/smoke .........head gasket.? ..........i dont recall my engine temp by any means....we were having fun............gees i hope i didnt screw my gt40 up from two hours of fun one april morning

[SquamInboards]

Any resolution yet?

[AB]

It could be a lifter that got plugged up and is no longer pumping oil through it. Or a rocker arm going bad. Sometimes tom isolate the sounds, imhave used a 1" diameter tube held up to my ear and move it around the engine area until the sound is really strong.

[acemech]

read thru the whole thread.....what ended up being the problem??