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HEY GUYS SORTA KNEW TO THE BOARDS, AND GOT A PROBLEM WITH MY 76 SPECTRA JUST HAD NEW BBF BUILT AND PUT IT IN THE BOAT DID THE CAM BREAK IN EVERYTHING WENT WELL MOTOR SOUNDS GREAT,PUT THE BOAT IN THE WATER EVERY THING IS GOOD UP TO ABOUT 1800 RPMS THEN I GET WHAT SOUNDS LIKE A ROD KNOCK.IT ONLY HAPPENS WHEN ITS UNDER A HEAVY LOAD,ON THE TRAILER WITH WATER HOOKED UP TO MOTOR AND PUMP IT SOUNDS GREAT AT HIGH AND LOW RPMS HAD THE TIMING ADJUSTED, VALVES ADJUSTED,NOW THEIR SAYING WATER IN THE FUEL I HAVE NO CLUE.FIGURED I SEE IF YALL HAD ANY SUGGESTIONS OR THOUGHTS.....ANY WILL BE APPRECIATED...THANKS:)devil
 

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if you think its water in the gas go grab a clear glass pull a fuel line and see if thats your problem. did you do anything to the pump? is this the 1st time out? or have you ran the boat before? with the old motor?
 

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Discussion Starter #3
Ive had the boat for a few years and ran it with no problems,i checked the impeller for any damage and the shaft for any movement and all looks good no vibrations or anything when its in the water... Ill try glass thang tonight and we will see...thanks
 

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Boat Nut
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Check the flywheel and PTO bolts, make sure they are tight. Control cable will transmit strange noises too, check to see if they are in a place they should not be, and move them around see if the noise changes or stops.
 

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Suggestion

Had a similar problem with my 460. It took awhile to find. After check everything on top, it turned out to be a broken inner valve spring. Pull the valve covers and take a look. Pretty easy to replace, but should have never happened in the first place and at Lake Powell to boot. Never had this problem with GM's.
 

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1800 RPM is about where you have the most water pressure coming from the pump, you sure you dont have a broken exhaust manifold and sucking water in the motor?

I would try to eliminate the easy stuff first.

It doesn't make noise on the trailer, why not?..The only thing that wuld change is the water pressure and engine load....How sure are you of the firing order?

GT :)hand (Not Gary Taylor :mad:)
 

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Mighty Mite is my brother, He's had the boat for a few years and it dropped a valve a summer or two ago. He just had a stock 460 built and he installed it. Everything minus the dropped valve was fine when the motor went so i'm assuming nothings changed and this is not his first rodeo with blowing S&*% up. Hes had several knowledgeable people look at it on the trailer and help set a base tune it should be real close.They thought it was a valve adjustment so I walked them through it and no change..Unfortunatley I live 3 hours from him so im not much help..Justin listen to these guys theres tons of good knowledge and a little not so good here well get this thing figured out Seriously if you want the Bahner for laughlin come get it...
 

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Did you check the U-joints? We had one starting to go bad last year and kinda sounds like what the prob is. ANY movement is bad!
Just my two cents
 

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I'm pretty sure that the timing is set at 12* initial and he uses 91 so...maybe water in the fuel thats the next step problem is it only does it in the water....
 

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i had a very similar problem. on the trailer she ran sweet. As soon as i put it in the water and put load in it it would knock and hesitate... My valve job was not done properly. A Good valve adjust later and no more issues and she runs smooth...
 

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riverside
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start simple with fuel filter.
then take a compression test,had similar
problem with bent valve that got worse.
good luck
 
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