Velvet drive "slipping"

[okelani]

I have a '99 340 dancer with 7.4 merc spinning velvet drives.. Last year I noticed what I thought was maybe just cavatation when revving up to 3500 rpm from 1300 rpm over a period of 3 to 5 seconds. This season it has happened more frequently. "it" just sounds like a little bit of thummping, port engine revs about 1500 r's more than s/b , sync gauge wacks out, and may best description of this is . . . " kinda feels like the clutch is slipping". also this season I must rev up from 1300 r's to 33-3500 rpm over 15 seconds which affects my get up on plane time time.

Any Thoughts anyone ??
John - Bowleys Quarters, MD:huh:

 

[larrytbull]

i had what i thought was a similar problem. my starbord engine was revving around 2500 rpm higher than port. and when I gave it throttle I saw the starboard jump to 5500+ rpm i figured it out after a few moments that there was no way my engine was revving that high and not blowing up. I wacked the tach for stbd motor and all of a sudden it went back down to proper rpm during that time synch guage was also way out of whack. was gonna check connections on tach during winter
hopefully you are sseing same issue

 

[go-hokies]

I have a '99 340 dancer with 7.4 merc spinning velvet drives.. Last year I noticed what I thought was maybe just cavatation when revving up to 3500 rpm from 1300 rpm over a period of 3 to 5 seconds. This season it has happened more frequently. "it" just sounds like a little bit of thummping, port engine revs about 1500 r's more than s/b , sync gauge wacks out, and may best description of this is . . . " kinda feels like the clutch is slipping". also this season I must rev up from 1300 r's to 33-3500 rpm over 15 seconds which affects my get up on plane time time.

Any Thoughts anyone ??
John - Bowleys Quarters, MD:huh:

What model of the velvet drive do you have? V5000 or straight drive? .. Either way, I would start with a pressure gauge (installed on temp sensor port) to try to figure out what your pressure looks like when you think its slipping. I have the V drive, I was loosing pressure in reverse (50 psi vs 300+ in forward). I was told there is not much you can do with these things without removing them and opening up. I am trying to limp through season as I hardly ever need reverse... Sorry....Others may have better advice...