Anybody have this problem before? Velvet drive issue

liquidsands said:

I just bought a 1979 Hershine 37' Trawler. 120 Lehman diesel / Borg Warner Velvet Drive. Left Eagle Harbor on Bainbridge Island, WA for 2.5 hour run. Tide with me all the way. Started out @ 8 kts +/-. After an hour or so speed kept dropping. Ended trip at 1.5 kts with same engine speed of 1500 rpm. Engine sounds beautiful. I was in a serious time jam up and left anchorage without checking trans fluid. When I noticed the radical GPS speed drop I first thought I must have read the tide tables wrong. Double checked...nope! Went back and looked at exhaust all seemed normal. Looked in hold briefly (boat was not in a position to stop due to rocks etc.) saw nothing amiss. Am suspecting clutch discs toast. Anybody run in to this kind of problem before?

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Harbor Marine in Everett probably rebuilds more Velvet drives than anyone else in the country. Call them +1 (425) 259-3285 and ext 103 is Mike Vogt.

If the clutches were slipping, there would be much heat generated. This is not happening & fluid looks good, you report.

Therefore if the shaft is turning at the expected speed, then more than likely the shaft key is sheared, and needs repair before the taper is really messed up (if not already, requiring a shaft pull).

If the shaft is not turning in gear, then something would have to b sheared in the VD or drive plate, and it would be noisy.

liquidsands said:

I just bought a 1979 Hershine 37' Trawler. 120 Lehman diesel / Borg Warner Velvet Drive. Left Eagle Harbor on Bainbridge Island, WA for 2.5 hour run. Tide with me all the way. Started out @ 8 kts +/-. After an hour or so speed kept dropping. Ended trip at 1.5 kts with same engine speed of 1500 rpm. Engine sounds beautiful. I was in a serious time jam up and left anchorage without checking trans fluid. When I noticed the radical GPS speed drop I first thought I must have read the tide tables wrong. Double checked...nope! Went back and looked at exhaust all seemed normal. Looked in hold briefly (boat was not in a position to stop due to rocks etc.) saw nothing amiss. Am suspecting clutch discs toast. Anybody run in to this kind of problem before?

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MY FINAL DETERMINATION OF CAUSE: not what you would expect...
Tested engine speed to shaft speed; same every time @1500rpm
Dove below to check prop was securely fixed and not spinning; solid
Trans temp under load after one hour running; could hold hand on it continuously
Fluid level in trans; less than 5 ounces low to top up after rotating heat exchanger ports vertical
Cleaned bottom; was actually pretty bad despite the guys diver supposedly having cleaned it recently
Checked linkages; all fully engaging, really almost perfect
WHAT THE PROBLEM WAS:
Did research and found Puget Sound current charts for current speed and directions.
Found a bit of time delay in the changing direction but not enough to skew expected flood tide direction. Did find that the approach to the harbor had a large underwater protrusion that causes the back eddy to get worse the faster the incoming flood gets. The course I was running took me in the worst spot I could be in for that particular trip and I was headed into a 5 knot reverse current. 1000 feet further out from shore in the main channel would have given me at least a 6 knot speed difference. The chart plotter I had was so small that the underwater reef looked much smaller than it actually was.
Found a program that runs on Windows or Mac that shows current directions and speeds based on the time of day with a sliding scale allowing you to simulate real time of day speeds and current directions over time. Allows you to choose time frame and see for those longer runs just what time to leave and have the current with you the entire run. It's a free program that has been out for a couple decades and I never heard of it before, called deepzoom. Link below... -tutorial video
Blog link.... DeepZoom Blog
free sub link.... DeepZoom Trip
Did a 7 hour run to my permanent moorage with the currents avoiding any back eddy areas completely and averaged 7.4 knots. Max speed going through Tacoma Narrows was 10.6 kts.
Conclusion boat is fine. No transmission issues and I was just being overcautious. Installed an HDS-8 inch plotter/fishfinder so I could see the smaller nuances better (so much easier on the eyes).
Thanks to all for your suggestions. It helped me to make the determination that the boat was safe to make the long run confidently. As it worked out, the boat is an even better deal than I thought. Getting her ready for a 2 month inside passage trip to Skagway, AK and back. Installed 36 mile Furuno radar, added to solar panels, installed new Icom radios, and upgraded skiff.

I’ve been boating in Puget sound for decades. Granted, there are some places that see 6 knot current at times, but to not realize you’re in it seems almost impossible to me. Situational awareness is a big part of navigation.
I would be concerned for you doing an inside passage trip where there are places you’ll see rip currents that will put you on the rocks if you are careless.

"The chart plotter I had was so small that the underwater reef looked much smaller than it actually was."
This can be an issue that can get you in big trouble. Also with VECTOR charts, objects can disappear when you zoom out. As stated above situational awareness maybe the most important thing in boating. This is not criticism as we can all improve in that category.

Not sure about 5 knots, but I’ve certainly had times when I was in an unexpected adverse current, and I was puzzled by an unusually slow GPS speed. Currents are unpredictable, and current charts on navigational apps like Navionics aren’t reliable.

One thing that I have found helpful is a speed through water gauge (I’m not sure what it’s called). My last two boats have had one, but unfortunately they only work for a few months after haul out because the little propellor on the bottom of the boat fouls quickly.

I have always checked currents once an A-B course is chosen, I will look for currents going in my direction. Arrival time often becomes the same leaving later.
As a sailor transiting active pass travelling at 5-6 knots was a waste of time when the current is running 4-5 against you.

To determine current effect, head straight into the current, write down the gps speed, then make a u-turn without touching the throttle and write down the gps speed going with the current. The difference in speed is the current.

High Wire said:

To determine current effect, head straight into the current, write down the gps speed, then make a u-turn without touching the throttle and write down the gps speed going with the current. The difference in speed is the current.

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Not to quibble, but wouldn’t it be half the difference?

If boat speed through water is 8 KN and current is say 4KN, your speed over ground is 4 KN and when you turn around your speed should be 12 KN.
12- 8 = 4 KN current

SteveK said:

If boat speed through water is 8 KN and current is say 4KN, your speed is 4 KN and when you turn around your speed should be 12 KN.
12- 8 = 4 KN current

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12 in one direction, 4 in the other. 12-4=8. Divided by 2 equals 4, which is the current.

I see your point

Yes sorry.