Trolling with a trawler

[Bob Nala]

Wondering if anyone has tried fishing with a 120 Lehman. Trolling speed of 2-3 kts. I know it is not recommended to idle the engine for very long, but would it be a bad thing to go at this speed for a couple hours once operating temperature is up?

Cheers

 

[RT Firefly]

Greetings,
Mr. BN. I see no problem with that but I defer to more educated minds. Thing about trolling is sometimes 3-4 knots is too fast and 15 knots is not fast enough...

 

[rslifkin]

I wouldn't be too concerned about it. Just get the engine good and warm first, and then give it a few minutes under heavier load when you're done to burn off any carbon. I wouldn't expect it to result in any issues.

 

[psneeld]

2 to 3 kts is pretty slow except for Striped Bass (East) or Salmon (West). Great Lakes not sure what for trout, OK again for salmon.

Couple hours no issue for a Lehman, if twins, shut one down and throttle the other up a bit.

 

[Turtle Blues]

Diesels attached to generators spend their whole high hour lives under 2k rpm. If it is up to temperature (thermostat working correctly) and burning clean it is not an issue.
Just curious, what fish is moving that slow?

 

[rslifkin]

Diesels attached to generators spend their whole high hour lives under 2k rpm. If it is up to temperature (thermostat working correctly) and burning clean it is not an issue.
Just curious, what fish is moving that slow?

Generator engines don't spend their lives running with almost no load, however. That makes a big difference. Much of the issue with idling along forever is not just the low RPM, but the very light load and correspondingly low exhaust temps.

Speed wise, in the Great Lakes, trolling at 1.5 - 2 kts for salmon, lake trout, etc. isn't uncommon. Many of the charter guys here troll with one engine shut down, the idle set as low as they can get away with, and still have to add drag in the water to slow the boat down more.

 

[Turtle Blues]

I would counter that the load underway is still constant and comparable, there is no coasting. Thus my note about the t'stat being necessary. And the time spent trolling insignificant except for commercial.

On the sportfish I had transmission trolling valves but that was at 4x the horsepower.
Never knew lake fish were that slow moving. Learned something today.

 

[psneeld]

Underway loading is really dependent on boat speed. Slow speed for 2 engines at idle is nothing like a genset that should be run at 50% or greater load (and often is)...but if not will run into issues much of the time. Thus with the main(s) too. Lot's of variables but generalities favor engines loaded are better off..... whether the main(s) or genset

Fortunately the Lehman engine can tolerate quite a bit of low loading.

 

[Marco Flamingo]

My prior owner trolled with an 80hp Lehman with two modifications. It has the optional 200lb heavy flywheel usually on the 120hp. It is shown in the Lehman owner's manual, but you can tell if you have it by the rear casing on the engine being about 3 inches long. He also had a hot water circulation system (potable water and Red Dot heater) that could be completely shut down. If either was left on during a long idle, engine temperature would drop. I can turn on the Red Dot full blast and if under 1K rpm, the engine temp drops.

The 200# flywheel on the 4 cyl. 80 hp Lehman allows me to idle smoothly (for a Lehman) at 550 rpm. Something that I rarely do. I'd rather mooch.

 

[Ken E.]

Most commercial fishing boats spend a majority of their lives idling with little load and no adverse effects. A few hours here and there trolling with your Ford Leyman is not going to bother it. I troll for salmon at about 2 kts in PNW and SE AK using trolling valves. Prolonged idling while trolling hasn't bothered my 6bt Cummins a bit

 

[JDCAVE]

The issue is the wear on the drive plate. A trolling gear is the ideal solution, but that costs $.

I played around with a sea anchor to drop the speed down.

 

[SteveK]

The biggest boat I fished from was a 24 center console. I fished most weekends. I cannot imagine enjoying it the same from the current sized boat. I did consider doing so on the GB36, but did not. Back in the70/80's when 8 salmon per person was the limit, I would catch the limit routinely. Today it is 2? and they are scarce. Cost to catch one is not worth the effort or cost.
BTW, this boat is set up for down rigger fishing, with net, two rods and some lures.

Naw, not going to happen. Admiral brought home a nice sockeye fillet bought for $16

 

[Hippocampus]

We also troll. Depending upon species and what we’re dragging and current either use low idle (600rpm) or fast idle(900rpm). Our Cummins QSC allows both. It’s common rail so I’m told no issues as long as every once in while you load it up. That routinely happens going back in.
We also trolled on passage as long as still on a continental shelf.. once in blue water haven’t had much success. Found offshore 6 kts or better was effective for mahi, yellowfin and such so load exists. Problem for us is striper. Best luck off the trawler has been find bluefish. Then go through that area with stuff very deep and very slow. Even to the point of popping in and out of gear or just stopped and use chunk bait. Totally different than when on a center console and you can chase birds. Striper is difficult off the trawler but have caught them and black bass at usual speeds. But seems totally random.
Might want to try fishing when anchored or off the dinghy. Actually since owning a trawler have had better luck doing that than with the big boat. Perhaps I need to change my technique and look forward to advice.
All in all agree with SteveK. We troll when going for a day or three non stop “ just because” and have a distraction. But have low expectations. It’s when anchored there’s a higher expectation and when we’re blowing a day in the dinghy. Boat came to us with overhead rod storage for 20 + rods, rocket launchers and scottys everywhere and four Scotty’s on the dinghy. P.O. obviously fished the boat and dinghy. Feel guilty not having a line or two wet.

 

[Northern Spy]

The biggest boat I fished from was a 24 center console. I fished most weekends. I cannot imagine enjoying it the same from the current sized boat. I did consider doing so on the GB36, but did not. Back in the70/80's when 8 salmon per person was the limit, I would catch the limit routinely. Today it is 2? and they are scarce. Cost to catch one is not worth the effort or cost.
BTW, this boat is set up for down rigger fishing, with net, two rods and some lures.

Naw, not going to happen. Admiral brought home a nice sockeye fillet bought for $16

You haven't fished lately then. Salmon are not scarce at all on the BC coast. Amazing runs for the last 5 or so years. Cohos jumping like trout all around the boat. Had one almost jump into the boat. Hit the side of the hull last week. Can look down and see the pinks. Big springs at 120'.

Not to mention the humpback, orca, and porpoise activity.

For the OP.

There are many Lehmans trolling on this side of the Strait. Most (every?) Taiwanese trawlers in the local marinas are equipped to troll.

I troll with my boat. If anything the prop pitch is the difficult thing to optimize. Slow enough to troll, fast enough to cruise. I almost wish I repowered with less HP.

Hopefully, the prop I have being worked on now at Vic Prop will be just right.

 

[Gulf Comanche]

I have moved my boat from Louisiana to Aransas Pass, Texas, but have never trolled in the Gulf with it. The species I’m aware of are red snapper, tuna, redfish. What types of lures or bait do y’all use?
The trip from my slip in Springfield LA was a long one, 12 days sailing, 2 days off, all on the Gulf ICW, solo, 2 run agrounds. No damage except captain’s ego.

 

[Hippocampus]

So far for reds a simple Carolina rig with frozen bait (shrimp works and easy to keep a tub in the freezer) at anchor has been most productive. Leave a few lines out once anchored and pull them in before sleep. Generally eat and hang our in the aft cockpit so no heavy lifting.
Off the dinghy streamers on a sink tip fly line casted near structure at slack. Trolling has been frustrating for redfish. So also interested in what soft or hard (have caught a few with soft at low speed) folks are using.

 

[SteveK]

You haven't fished lately then. Salmon are not scarce at all on the BC coast. Amazing runs for the last 5 or so years. Cohos jumping like trout all around the boat. Had one almost jump into the boat. Hit the side of the hull last week. Can look down and see the pinks. Big springs at 120'.

Not to mention the humpback, orca, and porpoise activity.

For the OP.

There are many Lehmans trolling on this side of the Strait. Most (every?) Taiwanese trawlers in the local marinas are equipped to troll.

I troll with my boat. If anything the prop pitch is the difficult thing to optimize. Slow enough to troll, fast enough to cruise. I almost wish I repowered with less HP.

Hopefully, the prop I have being worked on now at Vic Prop will be just right.

Correct, I have not fished lately. And I do not live/boat in your area. I have toured the south gulf island areas where I used to fish and see very few boats fishing in the previous hot spots. Few boats to me mean few fish. My favorite spot was along cabbage island east point area. There were hundreds of boats in the 70/80's there, fish were abundant.
Consider yourself fortunate to have the northern runs still producing well.

 

[jerry.kopf]

I troll successfully by pulling a drift sock/ sea anchor behind my 34 ft Europa. I can bring it down to 1.5 mph in gps. At this speed I catch mostly walleye in the Great Lakes. Bump up the speed another mile per hour and I’m good for salmon and trout.

 

[koliver]

Correct, I have not fished lately. And I do not live/boat in your area. I have toured the south gulf island areas where I used to fish and see very few boats fishing in the previous hot spots. Few boats to me mean few fish. My favorite spot was along cabbage island east point area. There were hundreds of boats in the 70/80's there, fish were abundant.
Consider yourself fortunate to have the northern runs still producing well.

Steve, you need to get out more. In front of my house (Rockfish conservation area so no hooks allowed) I have recently seen pinks jumping. My son routinely catches salmon near Thrasher, as do several avid friends. Likewise off Cabbage. Helen Point used to be reliable, but closed due to conflicts with ferries, so who knows? Orca reserve near N Pender used to be reliable, but now saving those salmon for the Orcas.
Years of no fish have decimated the crowds so now that there are fish there aren't so many chasing them. Good balance I suspect.

 

[SteveK]

Keith I went by your place and saw them jumping, as well as Cabbage and south Pender. What I am used to is seeing them being hooked and landed. Not seeing that, though of course it is happening, just not that regular.
Indeed at Port Browing spoke with a fellow cleaning the one salmon they caught. Maybe the odds are still better than the loto.
I get out as often as I can while still working to pay for retirement.

ETA: BTW I am also seeing less whales locally, and if they are not hanging around, you know there is not enough salmon.

 

[Hippocampus]

Interesting about whales. Up here if you see seals you see great whites. See either move elsewhere to fish.

 

[Pete Meisinger]

My 36 foot Albin was to fast for trolling the Great Lakes, although I did it a few times, even caught some Salmon. I had to drag a small sea anchor which kind of got in the way.

pete

 

[Bob Nala]

Thanks for the replies. Gave up a nice fishing boat for a trawler. No regrets. (good name for a boat) PO was good enough to wire for some Scotties. Prawning has been good on this boat. No time for some blood.

 

[ronobrien]

I wouldn't be too concerned about it. Just get the engine good and warm first, and then give it a few minutes under heavier load when you're done to burn off any carbon. I wouldn't expect it to result in any issues.

Agreed. You are not completely idling when trolling as you are actually pushing the boat. Good advise to run hard for 5-10 minutes afterward. The issue is increasing cylinder pressures that keep the rings seated on the cylinder walls. Overall not a big issue. Are you planning on fishing or catching? (chuckles)

 

[omoore]

2-3 is too slow for anything except salmon and trout. Where I live in NC the sped for MahiMahi and tuna are 7-11.

 

[rpackard]

The commercial salmon trollers in SE Alaska troll at idle speeds all day long, every day and get well over 15,000 hrs on their single diesels. But they do take care of the engines with proper oil changes.

 

[Erben Renewal]

I ‘trolled’ with a 140 Lehman (ADC) at 6-7kts for years all thru the GOM/Caribbean/Atlantic Seaboard with pretty consistent harvest results. Not sure about what to expect trolling at 2-3kts.

 

[SeaGator]

Low speed on a diesel is NOT detrimental for occasional periods such as trolling for a few hours. Lehmans are marinized truck engines made to work at various RPMs, including idling at truck stops over night or idling for hours during freezing weather to avoid trying to start up in low temps.

It annoys me to see the myth of "diesels have to be run hard" continue on forums and dock talk. Ask your diesel mechanic how many engines they had to rebuild due to being run too easy. I've never seen one. Just run your engine a little harder before and after trolling.

 

[rslifkin]

Low speed on a diesel is NOT detrimental for occasional periods such as trolling for a few hours. Lehmans are marinized truck engines made to work at various RPMs, including idling at truck stops over night or idling for hours during freezing weather to avoid trying to start up in low temps.

It annoys me to see the myth of "diesels have to be run hard" continue on forums and dock talk. Ask your diesel mechanic how many engines they had to rebuild due to being run too easy. I've never seen one. Just run your engine a little harder before and after trolling.

The "diesels like / need to be run nearly flat out all the time" thing is absolutely a myth. But extended idling isn't great for most engines either, particularly if that's a large portion of its operating time. Combustion temps (and exhaust temps) are much lower at idle, particularly on diesels. So things don't burn as cleanly, you get more carbon buildup (especially in turbos, etc.).

Some engines handle it better than others (modern common rail systems usually handle idling quite well), and it can take a while to be an issue. At the worst end of the spectrum is something like an old Detroit that will start to wet stack and smoke if idled too long, particularly if anything is in less than perfect condition or adjustment. Even that isn't a real risk of permanent harm unless it's run that way all the time. You may just get some extra smoke when you throttle up after trolling until the unburned fuel / oil junk burns off.

Periodic runs under moderate load will burn the buildup off. It doesn't take a WOT run to get things hot and clean, just a moderate amount of load.

 

[ronobrien]

The "diesels like / need to be run nearly flat out all the time" thing is absolutely a myth. But extended idling isn't great for most engines either, particularly if that's a large portion of its operating time. Combustion temps (and exhaust temps) are much lower at idle, particularly on diesels. So things don't burn as cleanly, you get more carbon buildup (especially in turbos, etc.).

Some engines handle it better than others (modern common rail systems usually handle idling quite well), and it can take a while to be an issue. At the worst end of the spectrum is something like an old Detroit that will start to wet stack and smoke if idled too long, particularly if anything is in less than perfect condition or adjustment. Even that isn't a real risk of permanent harm unless it's run that way all the time. You may just get some extra smoke when you throttle up after trolling until the unburned fuel / oil junk burns off.

Periodic runs under moderate load will burn the buildup off. It doesn't take a WOT run to get things hot and clean, just a moderate amount of load.

I agree that long idling isn't too detrimental to a diesel. Running it flat out as a requirement for long life a myth. However that said, the piston rings seat to the cylinder walls better under a heavy load (not necessarily flat out). So while idling, or light loading for extended periods is not a catastrophe, running them hard for a short periods afterwards is beneficial for ring seating and prevention of cylinder wall glazing. Diesels do like to work.