Twin disc Trolling valve

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Oct 15, 2009
I like to fish-salmon halibut-and would appreciate the usefulness of a trolling valve on a Cummins 6BT5.9 engine on a 34-36 foot trawler and any other concerns about such a combination may present.

You can only contact the transmission Mfg , and find out if this is an option with your unit.
RussNot sure if I understand what it is you are seeking. I installed a trolling valve in my boat over ten years ago, and it truly did help. My particular valve reduced my idle speed from 3.5 knots to 2.3 knots approximately. Much better for trolling King Salmon. As to concerns, the only ones I would have are whether you should be running your main engine at low RPM for extended periods. With my limited understanding, nearly any diesel that can maintain close to optimum cylinder temps while fishing is not going to be harmed by doing so. My trolling valve cannot be run over 1,000 rpm, which doesn't keep my temperature as high as I'd like, and at that rpm doesn't go slow enough for ideal King Salmon speeds. Only by running at dead idle am I able to go slow enough. This slow running can be compensated by getting up to a good hot cruise after fishing, thereby cleaning up the cylinders. However, as Fred says, your bottom line decision should be determined by a quality Cummins mechanic, with full understanding of the transmission/engine combination, and the actual trolling valve you will use. Once you determine what rpm you'll run at, then he can tell you what problems you might suffer.
I haven't really used mine as much as anticipated, due to my wife's inability to deal with slow rolling motion. She barfs all over my fresh caught fish. So, I really can't speak beyond what I have said.
Good luck, Carey

You need to troll very slowly if you're fishing for kings (chinook).* A couple of knots at most.* You will also have far better luck with kings if you fish with downriggers, which means you need a place to mount them that will keep their cables out of the props and rudders of your boat.

You don't have to troll so slow if you fish for silvers, and since they tend to work closer to the surface than kings, you can get away without downriggers although it's still better to have them.* There are some people who fish for silvers in BC using a large fly trolled very fast on the surface.

You don't need to troll at all if you want to fish for halibut. My wife and I have done a lot of halibut fishing up the north end of Vancouver Island. It's bottom fishing in depths between 120 and 350 feet. You use a one to two (or more) pound lead ball on the end of non-stretching Dacron line and bounce the bait along the bottom. The only time we use a motor for this is if we are trying to fish in a current that's too fast to keep the bait on the bottom at which point we use the trolling motor to hold station.

We do not use the GB for this because where we fish we are working pretty close to rocks and reefs and the GB would simply be to awkward to deal with in this situation. To say nothing of the fact that the diesels would be at dead idle most of the day because halibut fishing is in essence drift fishing.* We use a 17' Arima we bought for this purpose* (see photos). We also use the Arima for salmon trolling.* I think a boat like an Arima, Grady-White, Trophy, SeaSport, etc. make better platforms for salmon, halibut, and ling cod fishing on the inside waters of Puget Sound and lower BC than a recreational trawler.*

I'm not saying if all you have is a recreational trawler you can't fish--- you can fish if all you have is a big log to sit on.* But compared to a smaller, faster, lower boat like the Arima, fishing from our GB would be pretty frustrating and a lot more work.

A trolling valve will definitely help as far as trolling for salmon goes, as Carey describes above.* I have corresponded with some people who use a trolling valve in conjunction with dragging a large bucket or some other device to slow the boat even more.* I can only assume that the boats these folks have are able to be run at low rpms for long periods of time with the engines at sufficient temperature to avoid the risk of loading up the injectors or fouling the valves and cylinders.

-- Edited by Marin on Sunday 18th of October 2009 11:58:13 PM


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When we go hali fishing it's drop the hook in 200-300' of water, shut off the engine, crack a beer and a sandwich and wait for the rod to jerk. (dog fish for the first 1-2 hrs. then if we're lucky, a nice hali will latch on.)
Thanks guys. In response to an earlier response I know that it can be retrofitted to a Twin Disc transmission. What I was asking and got good responses to was whether the valve actually helped get the trolling speed down to where it should be for salmon.
Russf, remember when you ask a question on here that the answers are not required to be about the question. We all have answers we want to give and only occasionally will they be related to your question. Looks like you got lucky on this one. Don't expect it every time.

Yours truly tongue in cheek,

1.* Will a trolling valve slow you boat down? Yes.
2.* Can it be installed? It depends on your serial number. Ask the the manufacturer and be prepared for a big $$.
3.* Will it help you catch fish? Ahh, now there is the question. I have caught King's on many a boat without trolling valves or downriggers. The best bet, be at the right site at the right time. Without trolling valves you can circle and zig-zag to slow bait down.*
A well tended rod suffices for a down rigger. In Alaska you are limited on number of Kings per day so crappy gear may be best - that way you can spend whole day goofing off, err fishing.
4.* Looking like a fisherman is important though.*With the right boat gear you will feel better when you are skunked.
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