Engine Roll...454...Boat Engine

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  #1  
Old 08-17-09, 03:02 PM
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Engine Roll...454...Boat Engine

Recently my boat engine has developed what is call an engine roll, not a smooth idle, but a surging roll type idle. Also as I'm accelerating, the engine won't go past 2,500...I can push the throttle up underway, but it just won't go past 2,500. At idle I can do what I want, mechanical linkage 4 barrel, will open and roar powerful, but underway I just can't get past 2,500. I changed fuel filters, and checked spark plugs, everything looked fine. I guess I'll clean the carb, change the fuel pump and coil next, but was hoping for some good ideas...ran fine three weeks ago, but not now...

Please help, thanks,

Bill
 
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Old 08-17-09, 03:30 PM
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You mentioned everything but checking the timing, spark advance (if any), and any external valve, like EGR, PCV. Coil can break down and cause weird things to go on with performance. Changing it won't be expensive, nor difficult.
 
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Old 08-17-09, 03:49 PM
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I'm going to do a compression check, and see if the timing advances (I've had that problem before), and yes the coil is going to be first, I priced the fuel pump at $168, so that will wait a little bit...

Thanks,

Bill
 
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Old 08-17-09, 03:58 PM
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Not sure what model 454 you have, but the older ones used a spark advance using vacuum. Check to see if the hose is connected and if it is actually getting vacuum. Just don't stick it on your tongue. Did that back in the 60's, on my 409. Man, it was sore for a week.
 
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Old 08-17-09, 04:25 PM
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Originally Posted by chandler View Post
Not sure what model 454 you have, but the older ones used a spark advance using vacuum. Check to see if the hose is connected and if it is actually getting vacuum. Just don't stick it on your tongue. Did that back in the 60's, on my 409. Man, it was sore for a week.
Yes no hoses, mechanical advance I'm sure, I had a 1967 GTO, 400, no vacuum hoses on tongue there either........
 
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Old 08-17-09, 06:04 PM
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i would check for a restricted exhaust
 
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Old 08-17-09, 06:54 PM
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Good thought, I have dual 4" exhaust hoses, and water cooled exhaust pours out at idle and more so underway, but I will check it out...one thing I noted checking the spark plugs, were they all were that nice dry light gray color except for cylinders 3 and 4 which were a little wet looking....
 
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Old 08-17-09, 07:52 PM
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They may not be firing efficiently. Pull the distributor cap and look for "tartar" on the metal contacts. You can either replace it or do "dental" work on it with a grit wheel on a slow dremel.
 
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