loud thud coming from transom area inside the engine cavity

[Itried]

Hello iboats,

i’ve Posted once before on here and had great success with help. I recently pulled the lower unit seals and now that I’ve put the lower unit back on and buttoned it up and now it has a loud deep knock not from the motor but where the transom meets the motor. It’s got a rhythm and increases in pace with rpm’s. All help is appreciated.

i tried to upload a video but was unsuccessful. I can send one if needed.

thank you,

mike

 

[alldodge]

Don't upload a vid, put them on something like you tube and put link here
You can upload pics, but not vids

Going to need something like that because I don't see no way to dentify a knock without hearing it

 

[Scott Danforth]

When was the last time you pulled the drive fir the anual inspection of the alignment, gimbal, and u-joints

 

[Itried]

I just did gimbal ujoints the last couple of weekends and put it all back together today.

ill get a video up on YouTube ASAP. Thanks for the advice

 

[Itried]

Here’s the link to the video for the noise. I can put another if you guys need me to do something specific.

thanks

 

[Itried]

,https://youtu.be/6uCfLWCfyAk
here’s the link forgot to attach.

Even better - Inserted Video;

 

[Fun Times]

Itried, Just letting you know we moved your topic down into the Mercruiser stern drive sub-forum vs the Mercury outboard sub-forum where you had put it.

Your engine sounds internal engine related but first try pulling the drive off and restart the engine to see if the sound stops or changes.

 

[alldodge]

^^ Agree, that sounds is internal like a rod knocking.

Pull the drive and fire it up, no need of a water hose for a short run like the last. If you run it longer, just connect hose to thermostat housing.

If it is a rod, then its rebuild

 

[Itried]

Thanks all. I’ll pull the drive today and see if noise goes away. I put it away last year no ticks or knocks of any kind.

 

[Itried]

I am working on pulling the drive and seems very difficult to pull off. Could this have anything to do with this noise. I’ve got it about an inch off an seems stuck.

 

[Bt Doctur]

it must be in forward gear

 

[alldodge]

Being a V8 it might have a Bravo drive, and if so the shift connection may be hanging. Look on the starboard side of the drive and look for the cable and shift fork, and see if the latch needs to be lifted up so cable can be removed

 

[Itried]

Ended up getting it off by attaching the trim and raising it until it popped off a trick I found on another thread. Theres no noise when I start the boat without the drive on. Also, the gimble bearing is now broken so I’m guessing I didn’t do the alignment correctly. I’m ordering a new gimble bearing and I guess I’ll try it again.

 

[alldodge]

I’m guessing I didn’t do the alignment correctly

Have to agree, but man broken, that is bad. Do check the coupler before new bearing and reinstalling drive. Look real close at the teath on the coupler, and cracks around the rubber

 

[Itried]

AllDodge i have inspected teeth and look perfect. I’m unable to see rubber with the gimble in. I’ll give it a better shot tomorrow. I feel pretty dumb as the gimble isn’t broken but it was turned to the left to the point I could see the side so it looked like the race had separated. So thankfully the gimble seems to be in tact. If I screwed up the alignment after installing the gimble bearing would it make a noise like this?

 

[alldodge]

Check the U joints close
See if the gimbal bearing will fit tight into the housing with hand fitting first. If it appears loose you will need a shim/sleeve to get it tighter.

The bearing goes in with the slots facing forward. Use a tool that only makes contact with the outer race to install, nothing should be touching the center. If it appears it will go in good, place the bearing in the freezer for several hours. The cold will make the bearing shrink just a little which helps upon reinstall