Low speed trolling

[Chrisc161076]

I troll for bass but l've always gone as slow as l can whilst maintaining a full tail of cooling water. The engine is a featherweight running 10:1.

This year l want to troll slower.

Has anyone checked engine temps with a half flow coming out or so, is there much of a difference?

In my mind l think the engine will be fine, 10 minutes like this, then a return to where l started from with a good water flow and also the high oil ratio.

Thoughts please.

[pat777]

I came across this YouTube clip the other day and posted it in the British Seagull Outboard (YouTube Clips) thread. Basically it is attaching a tube to the water outlet to act as a syphon. The guy who posted the clip seems to think that it makes a difference to the flow at all throttle speeds, because you're not only relying on the rotor to pump the water. Might be worth a try.

[Chrisc161076]

Thanks Pat, l'll check that out. I know when l did motocross you could get stickers to put on the engine block so that you could see engine temps, so l might try the two together.

[Chrisc161076]

Pat, have you got link? Thanks

[pat777]

Having re read what I posted, I'm guessing you think the guy who made this cooling modification was the one who posted it here, but it was actually me who posted it after seeing it on youtube in the other thread. I was thinking of trying it myself, but it's kind of on the long finger at the moment.

Here is the link to thread I posted it in originally, there was a small bit of discussion about it.
viewtopic.php?f=2&t=4711&start=15

I''m no expert but judging by what I've read here in previous threads about cooling, I think as long as you have some water flowing out of the tell tale your plan should be okay, but I guess it would be better to find out exactly what the temperature difference was when the water flow was reduced. There was another thread on here before where lads were checking the temperature of their blocks with those laser thermometers

[pat777]

Here's a previous thread on the topic of low speed water cooling, I've not had a chance to read it yet myself but looks like a good bit of information in it.

viewtopic.php?f=2&t=1510&p=8891

[pat777]

Updated YouTube clip from previous thread.

[Stelios_Rjk]

Guys I don't know but for no specific reason I don't like those tubes. OK it is supposed that the pump pushes the water only up to the level of the outlet. Indeed but I doubt if anyone has taken into account the friction added because of the additional tube.

In such occasion I would reduce the diameter of the prop. More revs, less thrust.

[Adrian Dale]

just check the water temp with your fingers, if its hot speed up if its not, your OK

[headdownarseup]

well going by crude testing on century and 102 motors with clutches, when the engine is under load i.e driving/turning a prop at lets say half throttle, then the water temperature does rise quite considerably. (water jackets have been previously cleaned so no problems there).
when the motor is put into neutral, the temperature drops right down.

so with what your asking your motor to do, slow revs and perhaps reduced waterflow, as long as its not kept working like this for too long then you shouldn't have many problems. just give it the odd burst of throttle to push a bit of water through the block. i think as long as you've got at least a trickle of water coming out that's got to better than no water at all?
difficult to find the right engine speed thats slow enough for trolling but fast enough to keep the water coming through. trial and error or maybe a nice electric trolling motor. nice and quiet so dont scare the fish!

jon

[phil]

Some of the 20s and 30s motors used a hinged flat plate that could be dropped in the thrust line produced by the prop.reducing the available thrust for pushing the boat.
IIRC they were hinged and some had a line to trip and reset them.

[OldBawley]

This is how I troll. Sailing or rowing .

Seagull is for emergency.

I troll for Cornetfish and Barracuda.

[atoyot]

Guys I don't know but for no specific reason I don't like those tubes. OK it is supposed that the pump pushes the water only up to the level of the outlet. Indeed but I doubt if anyone has taken into account the friction added because of the additional tube.

In such occasion I would reduce the diameter of the prop. More revs, less thrust.

I'm the one who experimented with this mod, first with 1/4" i.d. Tygon tubing and then 316 stainless. The question of flow restriction due to friction is a good one.

Having not yet tried to qualify or quantify this, my observations on the water seem to suggest the velocity of the discharge is greater enough, through the modificaton, that it makes up for the apparent volume that used to simply fall out of the cylinder head. I could remove the mod and measure the output in a graduated bucket over a fixed time and rpm (using a laser tach), then repeat with the pipe on. Cool! A project.....

Here's an overall look at it:



Having a highly-accurate measuring device wrought by God Himself (my left hand...), it seems that the head runs at around the same temps give or take ~10C with or without this tube and NPT-to-compression fitting in place. In my video showing the Tygon tubing, I ran with 100 octane avgas and the tickover was more like a sewing machine than outboard.

The engine is barely working at that speed, and the water comes out about pee warm. It warms up a little more at moderate throttle - about where it quits "4-stroking" - then cools back to body temperature on wide throttle.

I would do it again in a heartbeat if historic replication were not at the top of my concerns. Next: the addition of a Nova-II ignition or Atom ignition module (have both in hand, for comparison).

[Chrisc161076]

Guys I don't know but for no specific reason I don't like those tubes. OK it is supposed that the pump pushes the water only up to the level of the outlet. Indeed but I doubt if anyone has taken into account the friction added because of the additional tube.

In such occasion I would reduce the diameter of the prop. More revs, less thrust.

I'm the one who experimented with this mod, first with 1/4" i.d. Tygon tubing and then 316 stainless. The question of flow restriction due to friction is a good one.

Having not yet tried to qualify or quantify this, my observations on the water seem to suggest the velocity of the discharge is greater enough, through the modificaton, that it makes up for the apparent volume that used to simply fall out of the cylinder head. I could remove the mod and measure the output in a graduated bucket over a fixed time and rpm (using a laser tach), then repeat with the pipe on. Cool! A project.....

Here's an overall look at it:



Having a highly-accurate measuring device wrought by God Himself (my left hand...), it seems that the head runs at around the same temps give or take ~10C with or without this tube and NPT-to-compression fitting in place. In my video showing the Tygon tubing, I ran with 100 octane avgas and the tickover was more like a sewing machine than outboard.

The engine is barely working at that speed, and the water comes out about pee warm. It warms up a little more at moderate throttle - about where it quits "4-stroking" - then cools back to body temperature on wide throttle.

I would do it again in a heartbeat if historic replication were not at the top of my concerns. Next: the addition of a Nova-II ignition or Atom ignition module (have both in hand, for comparison).

I think any account for friction for the short distance and smooth stainless steel and tygon tubing would be negligible, both considering any other loses in the system and the basis and assumption made in the calc would make the answer not accurate.

I would be interested in the results of the bucket test.

I think the most interesting test would be using the other proposed impeller. Pump curves are different due to the different impeller types and will have a different operating curve along the rpm range, l believe this could bring the most beneficial result. Last year when l was trolling and tried to reduce speed but maintain water flow, l noted that the water would drastically reduce at a specific rpm, this is where the pump falls off its curve.

I also don't want to trim the prop, although this would work.

Installing a four stroke outboard is an option, but not what l want to do, alternatively l could use an electric motor, however my boat is so small and light weight l don't know where or how l could mount it without compromising the transom, perhaps l'll post some pics when l have time and ask for suggestions.

Thanks for all those who have contributed so far for making this such an interesting post.

[Charles uk]

"I also don't want to trim the prop, although this would work."

Now this might be the most sensible idea yet, as it carries less risk of the tell tale emitting steam not water & the Captain failing to notice, as the lure is where the birds are feeding.

Marston used an aluminium disk to stop the prop working as well as it should, this would only work on a few models of Seagull depending on prop/shaft design.

Why not try some fabric strengthened Gaffer tape, wrapped around the prop blade tips like a bike tyre to reduce the operating blade area, or perhaps a childs bike tyre depending on prop diameter, or even an aluminium polo shaped disc held on with cable ties.
This way the risk of heat seizure is removed as the cooling system won't be compromised, & after you've caught your Marlin, 30 seconds with a sharp knife will get you home at normal cruising speed.