Bore one cylinder??

Ladder12

Cadet
Joined
Jun 20, 2010
Messages
8
I am looking at purchasing an older boat with twin Crusader 270 engines. During the sea trial, a problem developed in which the engines slowly lost rpm's without changing the throttle settings. During this time, the owner, who claims to be a mechanic, informs us that he has not put fuel in the boat in a couple of years and that it is probably just bad fuel. He is going to put new fuel in it and we scheduled another test.

The mechanic comes out and after starting and running the engines for less than a minute, he suspects a problem with the engines and checks the compression. Sure enough, the #3 cylinder in the port engine was building almost no compression. We put everything back together and start it up. Now this engine is making a lot of noise that was not present several days earlier. In discussions with the owner, he admits that he took the boat out again after the sea trial.

At this point, the mechanic tells me that we need to pull the engine to determine what is wrong with it. I make him an offer to take the boat at that time for the agreed upon price minus the mechanics cost for rebuilding to engine. He refused and said that he would keep the boat before giving it to me at that price. However, as we begin to leave that evening, the owner informs me that he may pay my mechanic to make the repairs and that we will talk when I return from vacation.

A couple of days later, I get a call from him telling me that he has already pulled the engine and torn it down. In his words, "Everything looks brand new except the one piston". I ask how he intends to proceed... Is he going to rebuild the motor or just the one cylinder. He indicates that he is going to repair only the one cylinder. Also, he states that he is going to take the block to a machine shop to determine if the cylinder was still round because there is some scoring inside the cylinder. I asked him if you could bore just the one cylinder without removing the crankshaft and the other pistons and he said yes. I told him to take the block to see the machine shop to see what they thought, but that I wanted myself and my mechanic to view the block and piston before they do anything to it.

I called him back four days later to find out that they have already bored the cylinder (without removing anything else) and are getting ready to put everything back together (with a new piston and rings for that cylinder only). Needless to say, I am not very happy as I have almost $1k in a survey, engine inspection, and boat lift at this point.

I have checked with several people who I trust and everyone agrees that you should strip everything down to the block to bore the engine. My feelings are that they will not be able to prevent the small pieces of metal that are honed off from getting down in the moter and that these will cause big problems in the future.

Does anyone have any experince in something like this? Would rebuilding only one cylinder make the others more likely to fail in the future. Do I run the risk of future problems from not tearing down the motor before boring it.

Any help would be greatly appreciated.

Rodney
 

Philster

Captain
Joined
Sep 15, 2009
Messages
3,344
Re: Bore one cylinder??

If just one piston -- and one piston only -- had damage, you could replace the piston. Something, for example, could have made one cylinder run lean and it could have toasted a piston.

A scored wall... if it is so bad as to require a re-bore... everything I know says they all need a re-bore, because one is going to thrown the whole thing out of balance. Maybe I am dead wrong, but once a cylinder needs a rebuild, the whole thing needs it.

The survey didn't cost you a thousand. It saved you 10,000 dollars.
 

EddiePetty

Lieutenant Junior Grade
Joined
Aug 25, 2008
Messages
1,008
Re: Bore one cylinder??

"My feelings are that they will not be able to prevent the small pieces of metal that are honed off from getting down in the moter and that these will cause big problems in the future."

Correct you are there my friend!!!!

Besides, who would remove a block and just repair one cylinder when the whole unit is right there before you?

Appreciating your investment, I think I would consider the expenditure as an insurance premium and walk away. This whole story has an odor to it.
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: Bore one cylinder??

on two stroke outboards it was permissable to bore 1 cyl only as all the pistons weighed roughly the same.
not so on v8 4 stroke marinized auto engines.
if one is bored its reccomended to bore the other 7.
wont be the first "rebuild" I ever redid due to honig or grinding dust taking out the crank bearings.
some machine shops will clean everything and all the assembler has to do is a final cleaning before assy.
other machine shops finnish the crank grind or the boreing and out the door it goes.
 

bigdan1

Petty Officer 3rd Class
Joined
Aug 9, 2010
Messages
95
Re: Bore one cylinder??

are you sure that he dint just replace the piston .....

if they bored out .010 with a similar piston ( weight) and that they took good care of covering all the internals , I woulndt worry too much ....


the best proof of this will be , when they restart the engine ,if it runs great ,
it`s ok !


I understand your frustration for your 1K ....but it is the name of the game

it`s still is boat ......

my opinion: if engine runs good now , and you are still interested , try it on water again and if runs great after 1 hour : oil pressure idles smooth : dont worry .....

my concern would be more about why this happened .......lean condition because of a stuck power piston in carb ?
get that fix !

have a good day !

Dan
 

Aloysius

Chief Petty Officer
Joined
Aug 21, 2010
Messages
484
Re: Bore one cylinder??

NASCAR engines were often unevenly bored.."cheatin"..as tech only checked #1 cylinder.

The piston probably weighs about the same as the others, so for all practical purposes you'll never notice it.

However, cleanliness is paramount in an engine. If the block isn't squeeky clean before/after the process, you'll NEVER get the metal out. Cylinders are cleaned with soap and water AFTER boring as this is the only thing that removes the really fine metal particles.

Change the oil filter repeatedly.

tough call.
 

JoLin

Vice Admiral
Joined
Aug 18, 2007
Messages
5,146
Re: Bore one cylinder??

Just ask yourself, is this the way you'd do it if it were your boat and you were planning to keep it?

This sounds to me like a 'fix it up just good enough to sell it' repair.

I'd walk away.

My .02
 

zbnutcase

Commander
Joined
Sep 19, 2009
Messages
2,055
Re: Bore one cylinder??

I agree, a tough call. Properly done it should be ok, but who really knows if it was? On the other hand, Chevrolet engines have amazing tolerance for abuse by hamfisted clowns who shouldn't even touch a lawnmower engine (and some even call themselves boat mechanics). Your money, your call.
 

rbh

Fleet Admiral
Joined
Mar 21, 2009
Messages
7,939
Re: Bore one cylinder??

Just a curiosity question, you used the words bored and honed.
While boring and honing both remove metal from the walls of the cylinder, honing on it's own has been a practice for when you just need to remove the glazing when installing new rings (and a piston I guess).
Which one was done???
 

TilliamWe

Banned
Joined
Dec 21, 2004
Messages
6,579
Re: Bore one cylinder??

I just find it hard to believe that it wasn't just a valve problem. When one cylinder (or even two or three) in a SBC is making nearly zero compression, it's usually a valve/valve seat issue. For that reason, I wouldn't trust these guys for boring out one cylinder.
 

Aloysius

Chief Petty Officer
Joined
Aug 21, 2010
Messages
484
Re: Bore one cylinder??

My guess is a piston pin slipped and damaged the wall.
 

bigdan1

Petty Officer 3rd Class
Joined
Aug 9, 2010
Messages
95
Re: Bore one cylinder??

1) when you bore out a cylinder you have to hone it , to give it the good surface finish .....

2) why woulndt it be a piston problem ? who are we to know what it was ?
the mechanic said the piston was damaged lets asssume it was.....

lets not paranoid ...even in a brand new engine , quite oftens the pistons bore wont be equal ....some times there is a letter stamped on piston

like a or c : different bore even from factory .......

do not loose a deal ( if indeed it is an interesting one ) ....
 

Ladder12

Cadet
Joined
Jun 20, 2010
Messages
8
Re: Bore one cylinder??

First of all, thanks to everyone for taking the time to reply. I know a little about engines (just enough to be dangerous) and what he is doing seems to be exactly what JoLin suggested... "a 'fix it up just good enough to sell it' repair".

Just a curiosity question, you used the words bored and honed.
While boring and honing both remove metal from the walls of the cylinder, honing on it's own has been a practice for when you just need to remove the glazing when installing new rings (and a piston I guess).
Which one was done???

I am not sure exactly what we done. I am not entirely clear what the difference is. Simply the word that popped into my little brain when I was typing.

The survey didn't cost you a thousand. It saved you 10,000 dollars.

Ain't that the truth. My wife and I are new to boating and we not really looking at a boat of this size (32'). When we stumbled upon this boat, we basically fell in love with it. The owner was telling us how well maintained it was and that there was "nothing wrong with it" which we realized was a lie bacuse his lips were moving. While the price was slightly more than we really wanted to spend (we didn't want a monthly payment), he was including several things (i.e. a dighny with 6hp motor, free use of the slip through next year) that made us agree with the price.

Then the surveyor spent almost 6 hours going from bow to stern and simply checked everything (I can still hear the rythmic beat of that little hammer in my mind). When she was done, we had proven that while there were things wrong with the boat, for the most part they were minor. A refrigerator that will not work on DC and the trim tabs that did not move were the only two "failures". Everything else was simply suggestions, expired safety devices, or things that the insurance company would want to see changed. However, then this issue appeared.

We are starting to get cold feet because we are not comfortable with the status of the repairs. While we are already looking at other boats, I think that we might follow BigDan's advice and see how the motor runs once everything is back together. Then we will sit down and attempt to re-negoiate a price. As I now know that there are the issues mentioned above, along with something that I feel was not repaired properly, he is going to have to come off of the original price to make the sale.

Once again, thanks for all of the replies.

Rodney
 

Aloysius

Chief Petty Officer
Joined
Aug 21, 2010
Messages
484
Re: Bore one cylinder??

For a few thousand, or less if the engine is still out, you can have it disassembled, cleaned, inspected, and re-gasketed and re-assembled.

don't pass up the boat just for a couple thousand dollars.
 
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