TomCat Formula
New member
I may go into too much detail but I hope my investigations help. The bottom line is that I am not sure there is anything wrong as both drives sound exactly the same and there are no chips/hairs on the magnetic drain/vent plugs.
This just started or at least was just noticed with both drives (at least I never noticed it before). 1988 Formula 311 SR-1 with hollowed out Silent Thunder swim platform and modified big blocks. The exhaust noise masks the sound in videos. One note, just previous to this discovery, I had just reduced the engine idle rpms to reduce stern drive engagement stress. The warm engines would hover about 1,000-1,100 rpms and I reduced that to ~750 rpms. I wonder if this is a new/induced vibration/noise due to that. When I re-set the idle to about 850-900 rpms the noise seems diminished BUT the I can still touch the top of the drive and feel a vibration…don’t have experience to know if this is new or normal. Drives were reworked/refreshed by previous owner and have about 60 hours on them.
There is a clanking noise coming from what seems like the tops (top cover) of the drives.
Discovery: I was flushing the motors/drives on the boatlift after an uneventful cruise and did not hear anything strange from the cockpit (over the noise of the engines/exhaust). My wife (standing on the dock, next to the boat up in the cradle lift, near the back of the boat and lower than my vantage point) said she hear a strange noise coming from below the swim platform. I did not think much of it because of all the racket from motors and exhaust flappers, etc…
The next day I motored the boat (15-20 minutes under its own power with full functionality and without incident) to the local boat ramp to pull it out for the month (as I will not be at this property for a few weeks). When I was flushing the motors again in the driveway my wife said the noise was still there…so I got out of the boat and listened.
Analysis: I have a clunking/clanking (metallic) noise which seems to be emanating from the tops of BOTH drives. I can FEEL it when I put my hand on the drive. I tried to minimize any additional damage/run time while I trouble shot the issue so here is what I know:
1) Both drives are doing the exact same thing. They seem to function fine but there is a distinct noise.
2) I started the starboard motor (on the hose) and shifted the starboard drive into reverse and drive while idling on the flusher hose…no real change in the noise and the shift was smooth and the prop spun as expected…remember, I just motored to the ramp without incident.
3) I drained the drives and found 2 to 2.5 quarts of Red Line Heavy Duty Shock oil drive lube in each drive (and NO water) and nothing on the magnetic plugs. I added new AMSOIL synthetic drive lube I got from you.
4) I restarted both engines (one at a time) and the sound did not seem to diminish.
5) Raising the rpms reduced the noise somewhat.
I pulled the observation cover on the port drive. Recall that I just did a fluid change and there was virtually no metal/hairs on the magnets and both drives looked identical.
I understand these drives were "worked on/freshened up" about 50-60 hours ago to accommodate 600hp motors.
(See Videos/pictures)
1) Is this too much "slop/play" in the top gear?
https://youtu.be/bg_z1A2qSk8
and
https://youtu.be/fdCb9rkdd00
Should I add additional shim/spacer to the top ring (see picture below) to reduce the slop/play?
3) When I replace the top observation cover, do I need to do anything (gasket sealer?) for the O-ring...it looks to be in excellent shape (are they re-usable)?
THANKS!!!
This just started or at least was just noticed with both drives (at least I never noticed it before). 1988 Formula 311 SR-1 with hollowed out Silent Thunder swim platform and modified big blocks. The exhaust noise masks the sound in videos. One note, just previous to this discovery, I had just reduced the engine idle rpms to reduce stern drive engagement stress. The warm engines would hover about 1,000-1,100 rpms and I reduced that to ~750 rpms. I wonder if this is a new/induced vibration/noise due to that. When I re-set the idle to about 850-900 rpms the noise seems diminished BUT the I can still touch the top of the drive and feel a vibration…don’t have experience to know if this is new or normal. Drives were reworked/refreshed by previous owner and have about 60 hours on them.
There is a clanking noise coming from what seems like the tops (top cover) of the drives.
Discovery: I was flushing the motors/drives on the boatlift after an uneventful cruise and did not hear anything strange from the cockpit (over the noise of the engines/exhaust). My wife (standing on the dock, next to the boat up in the cradle lift, near the back of the boat and lower than my vantage point) said she hear a strange noise coming from below the swim platform. I did not think much of it because of all the racket from motors and exhaust flappers, etc…
The next day I motored the boat (15-20 minutes under its own power with full functionality and without incident) to the local boat ramp to pull it out for the month (as I will not be at this property for a few weeks). When I was flushing the motors again in the driveway my wife said the noise was still there…so I got out of the boat and listened.
Analysis: I have a clunking/clanking (metallic) noise which seems to be emanating from the tops of BOTH drives. I can FEEL it when I put my hand on the drive. I tried to minimize any additional damage/run time while I trouble shot the issue so here is what I know:
1) Both drives are doing the exact same thing. They seem to function fine but there is a distinct noise.
2) I started the starboard motor (on the hose) and shifted the starboard drive into reverse and drive while idling on the flusher hose…no real change in the noise and the shift was smooth and the prop spun as expected…remember, I just motored to the ramp without incident.
3) I drained the drives and found 2 to 2.5 quarts of Red Line Heavy Duty Shock oil drive lube in each drive (and NO water) and nothing on the magnetic plugs. I added new AMSOIL synthetic drive lube I got from you.
4) I restarted both engines (one at a time) and the sound did not seem to diminish.
5) Raising the rpms reduced the noise somewhat.
I pulled the observation cover on the port drive. Recall that I just did a fluid change and there was virtually no metal/hairs on the magnets and both drives looked identical.
I understand these drives were "worked on/freshened up" about 50-60 hours ago to accommodate 600hp motors.
(See Videos/pictures)
1) Is this too much "slop/play" in the top gear?
https://youtu.be/bg_z1A2qSk8
and
https://youtu.be/fdCb9rkdd00
Should I add additional shim/spacer to the top ring (see picture below) to reduce the slop/play?
3) When I replace the top observation cover, do I need to do anything (gasket sealer?) for the O-ring...it looks to be in excellent shape (are they re-usable)?
THANKS!!!