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jenevers

how often do you take your engine up to maximum revs?

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When starting it, to warm it up (neutral).

When arriving at a bridge hole and finding that another boat is just starting to come through (reverse).

Rarely, if ever, in forward.

 

And you?

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Only once, on the Severn.  Full revs on a Kelvin K2 is about 750 rpm.  I was pretty well aquaplaning at that speed :)

 

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I did it the first time I went on to the River Weaver, just to see "what it would do".

57ft boat with 17x11 prop on Vetus M4.17 with 2.09:1 gearbox:  just over 2,100 rpm and 7.5 mph.

Didn't reach maximum projected rpm, even though the prop was a bit smaller than the recommended 17x12.

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1 hour ago, dor said:

I did it the first time I went on to the River Weaver, just to see "what it would do".

57ft boat with 17x11 prop on Vetus M4.17 with 2.09:1 gearbox:  just over 2,100 rpm and 7.5 mph.

Didn't reach maximum projected rpm, even though the prop was a bit smaller than the recommended 17x12.

Me too,R.Calder 20ft Norman,8hp outboard and according to the Sumlog thing, 8 knots!!

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For 5 full days of travelling back in March. 

 

Left West Stockwith on March 15th heading upstream on  the tidal Trent with 11 foot of fresh coming downstream. 

 

In some sections it was a struggle to achieve 2 mph.  5 days later  we arrived at the relative millpond of Newark 

 

We had far less problem with coke nuggets popping out of the exhaust stack for the rest of the summer :) 

Edited by cheshire~rose
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5 hours ago, Athy said:

When starting it, to warm it up (neutral).

When arriving at a bridge hole and finding that another boat is just starting to come through (reverse).

Rarely, if ever, in forward.

 

And you?

 

It doesn't sound as though you are mechanically sympathetic. 🤔

 

I was always taught not to rev a cold engine very high, and to warm it up under load at low to medium revs as quickly as possible.

 

Mind you that is with modern high speed engines, not slow revving vintage lumps, although I can't see why the size or speed should make any difference, as you are trying to ensure the cold, thick oil has warmed up and thinned before making the engine work too hard.

 

With regard to the original question, only when on rivers. 

Edited by cuthound
To add the last paragraph

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I don't recall ever running the engine on Helvetia at full revs, not even going upstream on the Thames when there was a swell on. We didn't have anything special for power, just a BMC 1.5 with a PRM 2:1 reduction box, but the shaft was about 17" below the waterline, which along with 15ft swims, gave the 17" prop a good grip on the water.

 

 

Edited by David Schweizer

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15 minutes ago, cuthound said:

 

It doesn't sound as though you are mechanically sympathetic. 🤔

 

 

Flattery will get you everywhere.

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2 minutes ago, Athy said:

Flattery will get you everywhere.

 

 

🤗🤗😂😍

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16 minutes ago, cuthound said:

 

 

 

I was always taught not to rev a cold engine very high, and to warm it up under load at low to medium revs as quickly as possible.

 

 

I was never taught any such thing, in fact I was never taught any way of starting a boat engine as far as I remember, I evolved my method myself and it works for me and my Gardner. Set throttle to just above tickover. turn key. As soon as engine catches, gradually advance throttle until it's on full.;. Run on full revs for about ten seconds. Then gradually retard throttle until it's back at tickover, wait about ten minutes and we're ready to go. 

 

Surely you are contradicting yourself: you say you want to warm it up "as quickly as possible"; the higher your revs, the quicker the engine will warm up, won't it>

You also suggest running the engine "under load". Since we always start the engine when the boat is moored, and since running the engine in gear when a boat is moored is discouraged (perhaps even forbidden), how is this achieved?

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19 minutes ago, Athy said:

I was never taught any such thing, in fact I was never taught any way of starting a boat engine as far as I remember, I evolved my method myself and it works for me and my Gardner. Set throttle to just above tickover. turn key. As soon as engine catches, gradually advance throttle until it's on full.;. Run on full revs for about ten seconds. Then gradually retard throttle until it's back at tickover, wait about ten minutes and we're ready to go. 

 

Surely you are contradicting yourself: you say you want to warm it up "as quickly as possible"; the higher your revs, the quicker the engine will warm up, won't it>

You also suggest running the engine "under load". Since we always start the engine when the boat is moored, and since running the engine in gear when a boat is moored is discouraged (perhaps even forbidden), how is this achieved?

 

Running an engine at high revs or full load when cold wears it out more quickly.

 

Anecdotally I have heard it said that 90% of wear takes place in the first 20 seconds after starting.

 

There is no contradiction, taking too long for an engine to warm up to operating temperature increases wear, so a balance should be found that partially loads the engine to warm it up as quickly as possible whilst minimising wear.

 

I adopt the roughly same practice as I do with a car. Start the engine and drive off normally as soon as practicable. Obviously with a boat this takes a little longer because having started the engine I them have to let go the mooring lines, whilst the engine is ticking over in neutral.

Edited by cuthound
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6 minutes ago, cuthound said:

 

 

 

There is no contradiction, taking too long for an engine to warm up to operating temperature increases wear, so a balance should be found that partially loads the engine to warm it up as quickly as possible whilst minimising wear.

 

 

Perhaps there isn't now that you have modified what you wrote before.

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3 minutes ago, cuthound said:

 

Running an engine at high revs or full load when cold wears it out more quickly.

 

Anecdotally I have heard it said that 90% of wear takes place in the first 20 seconds after starting.

 

There is no contradiction, taking too long for an engine to warm up to operating temperature increases wear, so a balance should be found that partially loads the engine to warm it up as quickly as possible whilst minimising wear.

 

I adopt the roughly same practice as I do with a car. Start the engine and drive off normally as soon as practicable. Obviously with a boat this takes a little longer because having started the engine I them have to let go the mooring lines, whilst the engine is ticking over ib neutral.

I have read somewhere that most engine wear occurs starting up.

Many years ago I remember looking at an old engine (can't remember if it was aero or boat) but it had a pre-oiler pump which pumped oil through the bearings prior to starting to minimise "cold starting wear"

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1 minute ago, Mad Harold said:

I have read somewhere that most engine wear occurs starting up.

Many years ago I remember looking at an old engine (can't remember if it was aero or boat) but it had a pre-oiler pump which pumped oil through the bearings prior to starting to minimise "cold starting wear"

 

Yes, most standby generators have several kW of crankcase heaters fitted to ensure both coolant and sump oil is at operating temperature because they are specified to take full load (actually 110%) within 30 seconds of start-up.

 

Some (mainly larger slow speed (400-600 rpm) engines had auxiliary "donkey engines" to circulate the lubricating oil prior to the main engine starting.

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In the early 90's the outfit I worked for managed a data centre design and build.  The standby generators in that job had big HP air bottles, the contents of  which were dumped into the turbocharger exhaust inlets to get the turbos up to speed so the gen set engine outputs were big enough quickly enough to take the specified load.

  Bloody noisy on demo!

 

On the other hand, the Air Traffic  Control centre we did in Bulgaria had a bllody great permanently rotating flywheel and genset which powered the UPS while the main standby generators got going.

N0

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6 minutes ago, BEngo said:

In the early 90's the outfit I worked for managed a data centre design and build.  The standby generators in that job had big HP air bottles, the contents of  which were dumped into the turbocharger exhaust inlets to get the turbos up to speed so the gen set engine outputs were big enough quickly enough to take the specified load.

  Bloody noisy on demo!

 

On the other hand, the Air Traffic  Control centre we did in Bulgaria had a bllody great permanently rotating flywheel and genset which powered the UPS while the main standby generators got going.

N0

 

Interesting, I have seen compressed air used to start diesels, but not to spool up the turbo. What a clever idea, assuming the engine starts before the compressed air runs out.

 

BT's (relatively inelegant) solution to the certain engines with poor load acceptance (specification was 70% load followed by another 40% within 15 seconds) was to start the engine at 1800 rpm (60Hz) and as it took load drop the governed speed to 1500 rpm (50Hz).

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8 hours ago, Athy said:

When starting it, to warm it up (neutral).

When arriving at a bridge hole and finding that another boat is just starting to come through (reverse).

Rarely, if ever, in forward.

 

And you?

I start up with a few revs above tickover (Gardner 4LW), then gradually go up to about 800 rpm whilst I untie, then set off on tickover and gradually build up to around 700 on canals. 
I could never put my engine onto maximum rpm from cold!😮 Surely you’ve got to wait until the oil gets through to the bearings at the very least😬

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After the rebuild we had loads of blue smoke and a couple of minor issues.

After sorting out the issues, our engineer started the engine and wound it up to full throttle.

Most of Napton disappeared in a cloud of blue black smoke. Smoke detectors went off, birds flew into each other, and the locals complained to the council about stubbling dirtying their washing.

After a while normal services was resumed and night turned back into day.

 

The engineer ( well known in this parish) wandered off probably muttering about precious owners treating their boats too well.

5 months on the situation is most improved. Assisted by going full bore down the river seven recently.

Retrospective reading of the lister running in guide suggests basically starting up the new engine, making sure it’s ok then working it hard for the rest of its days.

 

Therefore how often do we go full throttle, basically when smoke gets in your eyes, or in the last mile before our mooring.

 

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20 minutes ago, jenevers said:

 
I could never put my engine onto maximum rpm from cold!😮 Surely you’ve got to wait until the oil gets through to the bearings at the very least😬

I have no idea how long that takes. But when it really is a cold day, when I advance the throttle the engine builds up its revs much more gradually, perhaps that's why. I'm not a mechanically-minded person, I just know that what I do works for me and that (14 years after its rebuild) it seems to work for the engine also.

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Just realised this is in the ‘Gardner’ forum (not obvious when going in from VNC).

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21 hours ago, roland elsdon said:

 

Retrospective reading of the lister running in guide suggests basically starting up the new engine, making sure it’s ok then working it hard for the rest of its days.

 

IIRC, Lister generators had a life expectancy of 45,000 hours between major rebuilds in the 1960-70s

 

 

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