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Engine Trouble
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| Jdonohuejr |
Posted on 08/19/12 - 5:15 PM
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I have a 1967 16 custom with a 1986 90 HP Johnson.
I've been having issues with it stalling in neutral and at low RPMs but I've been able to deal with that. However, today I throttled down to hit a couple waves, and suddenly the motor sounded a little louder and with the throttle all the way down it wasn't able to go any faster that 10 mph or so. Luckily I made it back to the ramp. I checked under the cover when I got in and didn't immediately see anything out of place. When I flushed it out at home it seemed a lot louder than it usually does and it was more "growly" than normal.
Any thoughts?
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| djacksonrn |
Posted on 08/20/12 - 6:35 AM
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Check the compression in all cylinders, verify the prop hub is not spun.
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| Phil T |
Posted on 08/20/12 - 8:03 AM
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When was the last time the carburators were cleaned? Sounds like dirty jets and now the engine is bogging down (no faster than 10 mph)
Running the engine in neutral in the water or on the muffs while trailer will not show the problem since there is no load on the motor.
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| Jdonohuejr |
Posted on 08/20/12 - 8:29 AM
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I'm not sure when the carbs where last services, I've owned the boat for less than a year. It was running great until this happened, and it was very sudden, and it definitely seems to be louder. Would a clogged jet cause a performance drop so suddenly?
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| Phil T |
Posted on 08/20/12 - 9:37 AM
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Yes.
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| Tom W Clark |
Posted on 08/20/12 - 9:58 AM
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Would a clogged jet cause a performance drop so suddenly?
Yes, as would a loss of a cylinder (or two in the case of a V-4) from a bad power pack. A fuel simple restriction can also cause this problem.
You don't have a spun prop. You haven't suffered a sudden loss of compression. Start with the simple and obvious stuff first. Vent cap on gas tank open and drawing air? Primer bulb firm?
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| Sebastian |
Posted on 08/20/12 - 10:18 AM
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After checking the carbs and potentially cleaning them, maker sure all your fuel lines and gas tank are in good shape. If you have old fuel lines, they can deteriorate and send gunk into the carbs.
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| Gamalot |
Posted on 08/20/12 - 6:09 PM
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I would run with what Tom said. Check the simple and cheap stuff first, try a different fuel tank and hose and make sure the vent is open and clear.
If it is a power pack on one side I imagine the engine could sound louder and different with just two cylinders trying to make 2 dead ones go. Power packs tend to fail with zero notice so check for good spark on all cylinders. Another tell tail sign might be found by removing the spark plugs and finding wet ones in the offending cylinders.
What ever is the cause, don't try running it hard until the culprit is found and repaired.
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| Karlow |
Posted on 08/20/12 - 9:29 PM
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Run it on the muffs. Pull the plugs and take a look, They may be fouled. Clean them/ replace them, Run it on the muffs. Does the engine sound the same? Same idle speed? If that does not seem to change anything, shut it off and feel the end of the plugs. Are they all the same temperature? If not the cold one(s) is not firing.
If there are two cold plugs, suspect the ignition.
KP
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