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John P

Knock when you give it throttle

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When I start I don’t hear it at idle but soon as you idle it up it has a knock in it and sounds like it could be a rod. Wondering if there is any advice or treatment I can run in there to help? It’s a chaparral signature 300 with twin 350

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Asking for a little history here. How many hours on the knocking engine? Last oil and filter change? Has it been regularly maintained? Who knows, it may even be a U-Joint knocking in the out drive. Does the knocking noise change when you put her in gear while tied off in your slip?

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Carefully look at each spark plug for broken white insulators or odd colors.

Can also be a ignition problem. Check / replace rotor and or the cap.  Crank sensor sending a full advance signal. Or a camshaft is being fully advanced to quickly.

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On 9/27/2020 at 8:09 AM, SterndriveEd12 said:

Asking for a little history here. How many hours on the knocking engine? Last oil and filter change? Has it been regularly maintained? Who knows, it may even be a U-Joint knocking in the out drive. Does the knocking noise change when you put her in gear while tied off in your slip?

Have to check that as I’ve been boating for years but this is my first inboard out and I know when I purchased in May of this year it supposedly the one motor had been replaced do to flapper on exhaust allow water to get in motor wish messed it up, and it seems to be that is was  maintenance and taken care of. Early in the season I had a popping noise come out the throttle body so replaced plugs wires and cap an rotor and after that it seem to be getting alittle to much gas and as I said new to this type of boat but it still started and ran but didn’t idle the greatest so just stayed close and used the other motor to put down to beach and back. So got comin up river one nite and rain come up on us so fired it up and as I said it ran decent when throttled so made back home didn’t never hear anything. So next day came out to mess with it again to see if I could figure out again why would idle good and when started as I said didn’t hear anything but soon as I throttled alittle I heard the k ice coming from top of motor but idle back down which couldn’t hear and shut down. Now trying to come up with direction or to hear if anyone else has had issue

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