Trolling valve?

[maineman]

Hello all,
I keep reading about trolling valves. It seems like they are used on larger engines to allow travel at slower speeds.
How does it work?
And, does it do any harm to the engine?
Are they only used on older diesels that might soot up if run at low rpm for a length of time?
Thank you!

[ksanders]

A trolling valve reduces oil pressure to the clutch pack in the transmission allowing slippage.

Folks have used them successfully for years, but the transmission guy (one guys opinion admittedly) I talked to was not a fan of them.

[tiltrider1]

I am not a fan of them. People forget to change the valve and take off at full speed only to smoke the clutch pack. Expensive mistake that happens all to often.

Now if a boat comes with trolling valves, n big deal. Just don’t use them.

[Ken E.]

I have trolling valves on Twin Disc gears and like them for salmon fishing. The comment about ruining the clutch pack is true, if the valves are engaged over near-idle rpm. I addressed that by putting a lock plate on the throttle binnacle while fishing that won't allow greater than 1000 rpm. The plate attachs easily wing nuts and isn't removed until the valves are off. My trolling valves are a TD part, not an aftermarket 3rd-party product. They control trolling speed for fishing very well.

[Conrad]

Blue Sky (Nordic Tug 42) came with a Twin Disc trolling valve. As idle speed is approaching 4 knots, if I have folks fishing in the cockpit I engage the valve to bring the speed down to around 2 knots, which makes them happy. The throttle is not touched until the valve is disengaged, and fortunately I also have an indicator light at the helm that lights up when the valve is engaged.
Talking with a seasoned Lugger repair shop owner, I was told that as long as I kept the engine RPMs low there should be no problem.
Another not so seasoned mechanic suggested that I could use the trolling valve for low speed maneuvering at the dock. A really dumb idea.

[maineman]

Thanks!