Stuck Valves?

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Leviathon
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Stuck Valves?

Post by Leviathon »

Is it possible for exhaust valves to get stuck in closed position causing high compression and slow cranking of engine? Replaced cracked exhaust manifold that was pouring water into head - but not knowing when this occurred, I am wondering if maybe a valve or 2 is stuck closed. Turns over fast with plugs pulled.
Steve and Mary Levi
1973 32' Marinette Fisherman
SBC Crusaders
El Ohssa
St. Joseph, Michigan
barkleydave
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Re: Stuck Valves?

Post by barkleydave »

Does not sound good to me.... bent valve stems or worse? Others on here like Fast Jeff should be able to nail it down for you.


safe boating,

dave
1987 Marinette 29 FB Sedan
Retired Boat Accident UL and USCG trained investigator
Retired USCG Captain
railrunner04
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Re: Stuck Valves?

Post by railrunner04 »

My guess is bent push rods. Usually when water gets in its real nasty bent metal bits and carnage abound. I'd try pulling the related pushrods out of the affected cylinder if they are bent they must likely will not come out easily that will more or less confirm hydrolock. Id be concerned about the cam lobes as well
Moby Rick
FYC grosse ile mich
32ft F/B express
1971
T/318 Chrysler marine
EWRice
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Re: Stuck Valves?

Post by EWRice »

Valves stuck shut will not raise your compression. It will create a cushion effect. This is how displacement on demand works in cars.

Question 1: does it crank slow and smooth, or hit hard spots?

Question 2: with the plugs in and coil wire disconnected, does it still crank slow. Or does it sound normal.

Question 3: did you pull plug wires to change the manifold?

If it cranks erratic with the plugs in, smooths out with the coil wire off and you removed plug wires to change the manifold, check your firing order.
Muskegon Lake
1972 32' Express flybridge
"AL13"
Twin 318s
On board air & prime 920
1963 Thompson Super Sea Lancer
Graymarine 327
1961 Alumacraft 12'
'55 10hp Johnson
Leviathon
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Re: Stuck Valves?

Post by Leviathon »

Starting to think it might be electrical rather than mechanical. I pulled valve covers and everything looks normal. Manually pushed down valves and they all are free. No rust or anything. Nothing changes when you remove plug from coil. This is a "new to me boat" so have no history. I can eventually get engine to start and it runs well - I have another starter and I am going to try that out tomorrow. Battery is fully charged.
Steve and Mary Levi
1973 32' Marinette Fisherman
SBC Crusaders
El Ohssa
St. Joseph, Michigan
EWRice
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Joined: Thu Feb 04, 2016 12:37 pm

Re: Stuck Valves?

Post by EWRice »

Before you change starters, I have a simple test that anyone diagnosing electrical problems should know.

You will need a voltmeter that is accurate to less than half a volt.

Pre test, hook the volt meter to the battery and crank engine. If it drops below 10v, your battery is getting bad. Keep in mind a battery can be fully charged, but have low cranking amps. Even a new one. Never trust a static voltage reading on a battery.

Step one, put the negative test lead on the negative post of the starting battery for that engine. Put the positive test lead directly on bare metal of the starter field case (body). Watch the meter and have someone crank the engine with the coil wire off. If it reads less than half a volt, or 500mv, then move to step two. If it reads more than half a volt, you have a voltage drop on your negative side. Leave the lead on the battery and start moving the starter lead closer to the battery, starting with the engine block, negative battery cable, etc. Check at every connection until you get below a half a volt. Crank the engine for each test. This will narrow the location of the resistance.

Step two, hook the positive test lead to the positive battery post. Hook the negative test lead directly to the threaded post on the starter. Crank the engine and check your numbers. Proceed same as step one down the positive cable towards the battery. Common problem areas on positive side are the solenoid and battery switch.

If you don't exceed 3/4 volt between both sides of the system, then you more than likely need a starter, and confirmed your main electrical circuit is in excellent condition.
Muskegon Lake
1972 32' Express flybridge
"AL13"
Twin 318s
On board air & prime 920
1963 Thompson Super Sea Lancer
Graymarine 327
1961 Alumacraft 12'
'55 10hp Johnson
Fastjeff
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Location: Rock Halll, MD

Re: Stuck Valves?

Post by Fastjeff »

Hang I there. Sounds like it's the starter (or low voltage to it).

Jeff
"We live at the bottom of an ocean of air, not at the top." General Marvage Slatington
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