Engine Rebuild -- What's Actually Involved
06-28-2016, 09:01 PM
#22
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I had a chunk come off of the ringland of #6 and it busted off a 1/8" piece from the intake valve. Boat ran fine from idle up until about 3800 RPM. If you tried to lean on it, it would backfire through the carb. I originally thought I had a weak fuel pump causing a lean pop, or an ignition issue. Only after a compression test showed about 80 PSI in #6 did I realize I had a major issue. When I pulled it apart I found a chunk our of piston #5 as well. Compression was fine in that cyl.
If you are truly getting zero compression it almost has to be a really big hole in a piston or valve.
If you are truly getting zero compression it almost has to be a really big hole in a piston or valve.
Obviously not what I'm hoping for given that means full rebuild.
That being said, I wasn't given the compression # over the phone, so perhaps the "no compression" I was told was very low compression.
It seemed to -- just not above a certain RPM. It also had a hissing sound at idle, once the motor was warmed up.
06-29-2016, 05:25 PM
#25
Yeah -- the marina is doing that this afternoon... why they didn't do that as soon as they found out the compression was gone -- I'm not sure.
Doing some reading, seems like I'm hoping for something in the top end of the motor.
While I'm certainly in no position to debate this assesment (and fear it may be accurate), it does seem a bit strange to me. Even after the overheat, the boat was running absolutely fine, except with more than 3/4 throttle.
Doing some reading, seems like I'm hoping for something in the top end of the motor.
While I'm certainly in no position to debate this assesment (and fear it may be accurate), it does seem a bit strange to me. Even after the overheat, the boat was running absolutely fine, except with more than 3/4 throttle.
Motor will also tend to lay down at the upper end.
06-30-2016, 06:28 AM
#26
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Marginal injectors may not manifest their problems until at higher throttle settings when the motor needs the fuel but the injector can't keep up. Cylinder goes lean, detonation ensues, timing is retarded which delays the combustion event, elevates exhaust temps. Intake valves begin to tulip, valves and valve seats take a royal beating as do pistons etc. You may or may not hear, or more likely feel, a slight miss at cruise speed.
Motor will also tend to lay down at the upper end.
Motor will also tend to lay down at the upper end.
06-30-2016, 07:13 AM
#27
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Marginal injectors may not manifest their problems until at higher throttle settings when the motor needs the fuel but the injector can't keep up. Cylinder goes lean, detonation ensues, timing is retarded which delays the combustion event, elevates exhaust temps. Intake valves begin to tulip, valves and valve seats take a royal beating as do pistons etc. You may or may not hear, or more likely feel, a slight miss at cruise speed.
Motor will also tend to lay down at the upper end.
Motor will also tend to lay down at the upper end.
Injector testing WILL become a standard preventative maintenance item from now on.
06-30-2016, 10:59 PM
#30
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