"Better get a new engine..."!?

[RebelCobalt]

I posted a question a few days ago about my '98 VolvoPenta having trouble with cold starts. I decided to get a mechanic to look at it. And he called with very bad news. He said cylinder 1 has no compression - apparently the piston has burned out. He said the engine has the wrong spark plugs in it (they're too short), and this caused the damage. Fixing the one cylinder would be expensive (we're talking thousands in labor), and he recommended I buy a new (warrantied) engine block, for about $5k, as it's possible the other pistons are close to burning out!

I am in complete shock, having just bought this boat 2 months ago. I even had it inspected. And of course, I'll be getting a second opinion (maybe even 3 or 4). But my questions are:
1. Does this explanation (too short spark plugs) even make sense?
2. Does it really need a new engine block? That seems a bit drastic...

One point to note - in my last post I said it was a 5.0GL, but it is really a 5.0Gi (ie fuel injected). You can probably tell I don't work on engines much...

 

[Don S]

Re: "Better get a new engine..."!?

Bet it's not a hole in a piston, had it been, you would have had a lot of blow by and oil blowing out of the valve cover.
More likely a tuleped valve. Have your mechanic do a leakdown test to determine exactly where the problem is.

 

[crewscontrol]

Re: "Better get a new engine..."!?

Before I spent $5K on a new engine I would remove the spark plug on the suspect cylinder and insert a fiber optic borescope (most any mechanic worth his salt will have one) and take a good look at the top of the piston. You should be able to easily see a holed out piston.

If the piston looks OK I would suspect a burned exhaust valve or maybe a bad head gasket. Do a wet / dry compression test. If after squirting some oil in the spark plug hole the compression is still zero, you have a burned exhaust valve or maybe a bad head gasket.

If either is the problem, you will have to remove the cylinder head to fix it. This is a whole lot cheaper than a new $5K engine.

 

[6meter]

Re: "Better get a new engine..."!?

I'm guessing that your mechanic is a parts changer, not a mechanic. Complete motors fix all internal problems. That way he isn't wrong. Get #2 opinion. Leak down test first.

 

[RebelCobalt]

Re: "Better get a new engine..."!?

Many thanks everyone

 

[zbnutcase]

Re: "Better get a new engine..."!?

Bet it's not a hole in a piston, had it been, you would have had a lot of blow by and oil blowing out of the valve cover.
More likely a tuleped valve. Have your mechanic do a leakdown test to determine exactly where the problem is.

If this bozo thinks too short of a spark plug caused this, do you think he even KNOWS what a leakdown test is? Let alone OWN a leakdown tester??

 

[Alumarine]

Re: "Better get a new engine..."!?

If this bozo thinks too short of a spark plug caused this, do you think he even KNOWS what a leakdown test is? Let alone OWN a leakdown tester??

I agree, but maybe he means too hot, not too short?

 

[crewscontrol]

Re: "Better get a new engine..."!?

I do not claim to be a mechanic, but I did stay in the Holiday Inn Express last night.

Running "hot" or "cold" or "short" spark plugs does not significantly change the temperature inside the combustion chamber.

Hot spark plugs are designed so the plug itself runs a little hotter usually to burn off deposits and keep the tip clean(er).

Cold spark plugs are designed to run a little cooler for what ever reason.

Short spark plugs??????????

On the other too long spark plugs may extend into the combustion chamber far enough to actually hit the top of the piston at TDC. This can damage a piston.

 

[Aloysius]

Re: "Better get a new engine..."!?

"short plugs" are used to prevent oil fouling. Won't damage the engine at all.

Was crewing on a road racer, driver burned a piston (long story). Only pistons available were 0.020 over, so we "bored" the block with a turkeyturd hone. Needless to say, not much oil control, but it ran ok, but fouled plugs. I told the owner to use 1/2" reach plugs in the 3/4" plug holes. Finished the race, went to the runoffs. used several quarts of oil in 30 minutes, but it carried 20....

 

[haulnazz15]

Re: "Better get a new engine..."!?

Colder plugs are better in forced induction applications (supercharged/turbocharged).

 

[BaileysBoat]

Re: "Better get a new engine..."!?

Lots of great insight on this thread. Agree with the hot/cold plug explanation by crewscontrol. Agree with DonS as usual about hole in piston.

Get another mechanic. The original issue was hard starting cold, not lack of power or misfire. Get another compression test done by a real mechanic and post back.

 

[littlebookworm]

Re: "Better get a new engine..."!?

Thank the "mechanic." Remove your boat and take it to someone who can diagnose and repair a marine engine. I have to "Amen" all the advice you've been given. That sparkplug is not your problem and din't cause a hole in a piston. If you had a holed piston, your engine would run like sh... and smoke like a house on fire. You need a compression test, a leakdown test, and probably a valve job, costing well under $1k. Good luck. Hy

 

[TilliamWe]

Re: "Better get a new engine..."!?

Bet it's not a hole in a piston, had it been, you would have had a lot of blow by and oil blowing out of the valve cover.
More likely a tuleped valve. Have your mechanic do a leakdown test to determine exactly where the problem is.

My thoughts exactly, Don!

 

[Joshua Nichols]

Re: "Better get a new engine..."!?

If this bozo thinks too short of a spark plug caused this, do you think he even KNOWS what a leakdown test is? Let alone OWN a leakdown tester??

Dang everyone should own a leakdown tester .. Great little tool.. I love the Bozo bit too..
I would like to know how he came up with a hole in the piston.. It bites to have to use a repair shop. Bet he charges $100 or more for the compression test and didn't come up with viable evidence of the problem.. Seems like he is wanting to sell parts for his shop.. Maybe he makes a percentage.. Get another opinion.. I am going to subscribe to this tread to see what happens.. Oh and just alittle story for ya.. I see it's number one showing to be bad.. Well I had a fella who worked with me tell me that a engine was shot cause the first cylinder he checked had zero compression.. No reason to check the others.. Made me kinda go hmmmmm.. So went and stuck mine in it to see.. Had 120.. His valve core had blown out in his tester.. Just a thought.... Also a question.. Cold starts?? So if its warm it starts and runs fine?? Thats not a hole in the piston.

 

[Aloysius]

Re: "Better get a new engine..."!?

Gotta tell ya, these new boroscopes are great! New lighted Snap-on units are outstanding.

 

[RebelCobalt]

Re: "Better get a new engine..."!?

Really appreciate everyone's comments. I know 1000% more about engines now than I did 4 days ago. I'll be visiting the mechanic tomorrow so he can show me what he's done, and I'll be peppering him with questions. If I can get it to another mechanic this weekend, I will. I called one (recommended by a colleague) that actually talked me through the tests folks here mentioned, so I have more faith he might be able to help me fix my boat, not just try to sell me a new one...