Engine Blow By?

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jmw129

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Hey guys this may seem like stupid questions but I just bought a boat with a 1985 4.3 V6 and my mechanic told me the following when he timed the engine.

The engine has equal compression in all 6 cylinders in the low 120's. Now my mechanic also told me that I have engine blow by and that is an indication of weak piston rings. Told me the engine is "Tired."

I contacted the guy who I bought the boat the from and he is claiming the following while I should consult another mechanic for advice.

The seller claims that you cannot have compression in the 120's and weak rings at the same time. Is this true?

My mechanic told me this engine should have compression in the 150-170 range and 120's for a 4.3L V6 is weak. He also told me that the engine was burning a lot of oil (Blow By) and the heads were banging like they were not getting enough oil.

Any recommendations?

Is there any oil additive to raise compression without rebuilding the engine? I know Rislone has a ring sealer / compression repair additive..

My mechanic was offended and said the seller is nutts and didn't appreciate being insulted by this guy.

Who sounds more correct or accurate, my mechanic or the seller?
 
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joewithaboat

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Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

Have you had the boat out on the water?
How does it run?
How many hours on motor?
I wouldnt worry too much about the comp test in the 120's yet, they are all the same so that is good.
Banging coming from heads is not good, never heard that discription before, but you need to figure that out.
good luck!
 
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jmw129

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Engine Blow By?

I need some clarification on what causes engine blow by?

Weak Rings?

Bad heads?

Bad or faulty fuel pump?

Other reasons?

Look forward to hearing from people who have dealt with engine blow by & how they fixed the problem.
 
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John_S

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Re: Engine Blow By?

Some blow by is normal. Excessive is generally a worn out engine, mostly worn rings, but any cylinder damage, or hole in piston. Heads, probably not unless extreme valve guide wear. Are you burning oil?
A faulty mech fuel pump can leak gas into oil, but you would be able to smell it.
What engine are we talking about?
 
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jmw129

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Re: Engine Blow By?

According to the dip it appears that I am. The engine is a 4.3 V6 1985 OMC.

How much blow by is considered normal?
 
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dollarten

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Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

Before you get some knee jerk reaction statement like , the heads are banging ?? , I would get a cylinder leak down tester . This little device screws in the spark plug and with a little calibrating tells you what percent of leakage you are getting through the rings A good engine should have less that 10% leakage . Even healthy engines will have some crankcase fumes coming out of the breather . I would have to do some checking but, I think the compression ratio got increased on the later 4.3 engines and would give a higher . Marine engines very seldom get tired seeing that they are operating in an almost dust free environment , they usually have some catastrophic failure i,e;water ingestion due to various reasons , dropped valve , broken connecting rod . Serious overheating will also render an engine inoperable
 
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joewithaboat

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Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

Because all holes checked the same 120, I would say that if you are getting excessive blow by it would be from low ring tension or worn valve guides. Low ring tension is usually from being run HOT more than once. Valve guides wearing could be from being run forever on dirty oil usually covering the valve train in sludge. Being just generally worn out in a small boat I would think would be unlikely most wont see that much time on the water. Prob got hot at some point or run low on oil. For what it is worth an engine will run with quite a bit of blow by, just keep an eye on the oil level.
Have you had it out on the water yet?
 
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John_S

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Re: Engine Blow By?

If your crankcase oil level is rising, it is either water or oil. An overfilled crankcase will "foam" and cause more blow by.

Normal would be a small amount seen at idle.
 
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jmw129

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Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

No didn't take it out on the water at all.

My mechanic had me all worried that the engine is worn or tired and also said I had a problem with my fuel pump pushing gas backward? but it still ran?

Told if I took it out before replacing the fuel pump that the engine would choke out on me..

So I have been afraid to even attempt it because I have broken down before and it really sucks.

What about using cleaner for the heads such as seafoam or some other brand?

I also seen online there is a compression repair / ring sealer by Rislone check it out: http://www.barsproducts.com/4444.htm

Vacuum gauge testing?
 
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dan t.

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Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

Blow by from worn valve guides? Not on this planet.
 
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joewithaboat

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Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

dan t. said:
Blow by from worn valve guides? Not on this planet.
Click to expand...
My aren?t we helpful :D
Not really "blow by", but "suck by", sucks unmetered air past the intake valve along with lots of oil in some cases. O/P said it was burning a lot of oil. Sinse compression test shows all 6 holes to be the same that pretty much rules out head gaskets and burned valves. Which leaves rings and guides. :rolleyes:
 
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dollarten

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Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

joewithaboat said:
My aren?t we helpful :D
Not really "blow by", but "suck by", sucks unmetered air past the intake valve along with lots of oil in some cases. O/P said it was burning a lot of oil. Sinse compression test shows all 6 holes to be the same that pretty much rules out head gaskets and burned valves. Which leaves rings and guides. :rolleyes:
Click to expand...
Get it running with some ear muffs first to see what it sounds like without any outside coaching an if it sounds good at that point , hook it to your tow vehicle and back it in the water and put it under load and see how the engine runs then . This way you won't have to row it back if the " fuel pump is running backwards " like your mechanic says If the engine will pull up to 2500-3000 rpms for a couple of minutes , it is probably safe enough for an on the water test . I would get another opinion on the engine . I try not to be offensive on the internet but , your mechanic sounds like a mink oil salesman. This ordeal sounds like some sleazy auto repair shops that will find all sorts of things wrong with your car when it is on their hoist
 
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joewithaboat

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Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

dollarten said:
Get it running with some ear muffs first to see what it sounds like without any outside coaching an if it sounds good at that point , hook it to your tow vehicle and back it in the water and put it under load and see how the engine runs then . This way you won't have to row it back if the " fuel pump is running backwards " like your mechanic says If the engine will pull up to 2500-3000 rpms for a couple of minutes , it is probably safe enough for an on the water test . I would get another opinion on the engine . I try not to be offensive on the internet but , your mechanic sounds like a mink oil salesman. This ordeal sounds like some sleazy auto repair shops that will find all sorts of things wrong with your car when it is on their hoist
Click to expand...

Well said ! I agree, I would have already had it in the water. As i stated an engine will run with quite a bit of blow by. But.... The fuel pump thing sounds a little wierd, never heard of that. Fuel prob/leaks in a boat are no joke.
I also vote for a second look from a new mechanic. They uaually look at it for free.
Good luck!
 
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jmw129

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Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

Yeah I agree guys. Sounds like I need a 2nd mechanic to give his thought on the engine. Only thing that sucks is the engine is winterized so I would have to pay for that again :(
 
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dollarten

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Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

jmw129 said:
Yeah I agree guys. Sounds like I need a 2nd mechanic to give his thought on the engine. Only thing that sucks is the engine is winterized so I would have to pay for that again :(
Click to expand...
You can till check check the blow by ( compression leakage through piston rings ) with the engine cold with my previous mention of using a cylinder leakage tester . . this type of a test is used on a non running engine in order to obtain results
 
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jmw129

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Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

dollarten said:
You can till check check the blow by ( compression leakage through piston rings ) with the engine cold with my previous mention of using a cylinder leakage tester . . this type of a test is used on a non running engine in order to obtain results
Click to expand...

In the past I have done a compression test but not a cylinder leakage test. Could you provide the steps in which you perform your cylinder leakage test? Is there a site such as you tube showing how to perform this type of test?

Thanks!
 
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dollarten

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Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

Re: 4.3L V6 1985 Compression 120's and Weak Rings.. Is The Engine Junk?

jmw129 said:
In the past I have done a compression test but not a cylinder leakage test. Could you provide the steps in which you perform your cylinder leakage test? Is there a site such as you tube showing how to perform this type of test?
Go on E Bay and type in ,, Cylinder leak down Tester and look at the one in the red box . This is the two gauge unit , don't get the one gauge model . They are quite affordable . there is couple good ones on You tube , that show this procedure Just to add a few more things It is OK to see some crankcase vapors coming out of the breather hose that points to the air silencer and you will smell a little blow by when you come off plane and return to idle as there is not enough vacuum at the engine silencer to pull the vapors inn . If the crankcase vapors are coming out like the like a cigarette burning . You are OK but if it looks like someone exhaling cigarette smoke , you may have a problem . Get the leak down tester and and have some fun with it . You will have a sense of accomplishment when you master it it..************ one more thing (s) you will need an air compressor and when you position the particular cylinder that you will be testing , position the piston a few degrees past top dead center as this is where the most wear will be and find a way to lock the crankshaft so it will not turn when you put air in the cylinder. Good luck
Click to expand...
 
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jmw129

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Re: Engine Blow By?

The small tube that is located on top of the valve cover does not have the rubber tube connected to the air filter / housing around the carb. So with this tube not being connected, I did see a small amount out on a almost regular basis / consistent basis coming out of this tube while running in idle is what I seen when my mechanic timed the engine before winterizing the engine. Wasn't a huge amount coming out but I have been told that when you up'd the RPM's you would then see the blow by with alot more smoke coming out?

Is that an accurate statement?
 
Bondo

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Re: Engine Blow By?

jmw129 said:
The small tube that is located on top of the valve cover does not have the rubber tube connected to the air filter / housing around the carb. So with this tube not being connected, I did see a small amount out on a almost regular basis / consistent basis coming out of this tube while running in idle is what I seen when my mechanic timed the engine before winterizing the engine. Wasn't a huge amount coming out but I have been told that when you up'd the RPM's you would then see the blow by with alot more smoke coming out?

Is that an accurate statement?
Click to expand...

Dude, ya bought a 27 year old boat,.... It Ain't brand New...
It don't have a problem Now,...

Go run it, 'n Enjoy it...
 
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