knocking sound in transmission

[Pilot]

When I put my starboard engine in drive I get a tapping/knocking sound. It did it once before but went away, now its consistent and appears to be affecting performance versus the port engine. Any ideas?

 

[KevinC]

When I put my starboard engine in drive I get a tapping/knocking sound. It did it once before but went away, now its consistent and appears to be affecting performance versus the port engine. Any ideas?

Check/replace your spark plugs and if that still does not fix it move on to wires. When doing the plugs also look for any signs that there could be water dripping and burning off.

The 8.1s with V-Drives will appear to run smooth but a misfire will sometimes be evident by noises from the transmission. I have heard transmissions that sounded like marbles running around in them that turned out to be plugs.

-Kevin

 

[Jus Cruisin]

Check/replace your spark plugs and if that still does not fix it move on to wires. When doing the plugs also look for any signs that there could be water dripping and burning off.

The 8.1s with V-Drives will appear to run smooth but a misfire will sometimes be evident by noises from the transmission. I have heard transmissions that sounded like marbles running around in them that turned out to be plugs.

-Kevin

Exactly my case. I did both plugs and wires. I now know nousy trans, time for a tune up

 

[Pilot]

Exactly my case. I did both plugs and wires. I now know nousy trans, time for a tune up

Thanks for the feedback. I am curious why it only happens when I put it in gear, even at an idle it knocks.

 

[villain style]

Check your oil to make sure it is not milky with water intrusion. Just went thru this same scenario with someone else who now needs new risers and manifolds..

 

[boatrboy]

read this from the top
http://clubsearay.com/index.php?thr...ssion-when-i-put-in-gear.103485/#post-1341994

 

[D Bell]

My starboard Hurth HSW 630 Transmission on 7.4L MPI with 650 hrs has a whirling sound when we engage and idle out of the dock. Does it in forward and reverse. Port side is perfectly quiet and there are no running problems. Changed AFT this past weekend and still get the whirling sound. Any thoughts?

 

[Pilot]

UPDATE
Thanks all for the input. I replaced the plugs and it solved the problem. Its sort of counterintuitive that this was the cause but in the end it solved the problem and no more knock. My mechanic explained that marine engines run at much higher RPM's and are much more "balanced" versus car/truck engines. Thus a single bad plug or cylinder or injector could create this situation if off by more than 5% from another cylinder. It ran fine without being in gear, although even in neutral, the engine would not maintain a smooth consistent RPM, rather, it would sort of drift a little higher, then lower etc,. I might add also that the plugs were changed in both engines @ 120 hours ago.

 

[boatrboy]

UPDATE
Thanks all for the input. I replaced the plugs and it solved the problem. Its sort of counterintuitive that this was the cause but in the end it solved the problem and no more knock.

I felt the same way when it solved my problem!

 

[techmitch]

UPDATE
Thanks all for the input. I replaced the plugs and it solved the problem. Its sort of counterintuitive that this was the cause but in the end it solved the problem and no more knock. My mechanic explained that marine engines run at much higher RPM's and are much more "balanced" versus car/truck engines. Thus a single bad plug or cylinder or injector could create this situation if off by more than 5% from another cylinder. It ran fine without being in gear, although even in neutral, the engine would not maintain a smooth consistent RPM, rather, it would sort of drift a little higher, then lower etc,. I might add also that the plugs were changed in both engines @ 120 hours ago.

I felt the same way when it solved my problem!

Drive your car or truck "up hill" at 3xxx + rpm's for 120 hrs.