Engine stalls when changing direction

[NigelD]

I recently purchased a 2001, 37 foot narrow boat with a Beta marine 3 cylinder 28 hp diesel engine and PRM 80 gearbox. When I change direction quickly i.e. lining up or slowing to enter a lock, the engine often dies on me (annoying and dangerous). Tickover is moderately low (perhaps too low) and I am not sure if the torque needed to stop the propeller and reverse it is enough when going quickly through the idle position. Normally of course, I engage drive slowly and here, I have no problems.

 

I can increase the idle speed but the gearbox then makes a horrible crunch as it engages. The gearbox is about 1 year old and has ATF in it, PRM recommend this (DEXRON III) but to be honest seems to me to be far too thin and I think a thicker oil would allow the “clutch” to slip a little bit when changing direction rather than “crashing” into gear as it does. The prop spins very freely and there seems to be no tight spots etc. Cable adjust also seems OK but I will check this again next time I am on the boat.

 

Any ideas?

 

[MtB]

 

Any ideas?

 

 

Well the obvious one is don't do it! Train yourself to think ahead slightly, and disengage from 'ahead' a second sooner.

 

Then the problem won't exist...

It isn't kind to the gearbox to slam it from ahead directly into astern anyway.

[RLWP]

Yes - don't put anything other than ATF in that box! It has two metal cone clutches. I have worked on a similar box which had been fed the wrong oil, it slipped badly all the time

 

Richard

[Alan de Enfield]

Comparison - do you slam your car into reverse whilst still moving forward - if you do, is it a similar noise ?, if you don't, why would you do it on your boat ?

[MtB]

Despite it being bad practise, we are still avoiding the issue of the engine stalling when moving sharply from ahead into astern. The engine shouldn't be stalling really anyway.

[bizzard]

Could be idle speed too slow, or resistance on the prop shaft, over propped or nackered batteries causing the alternator to work overtime.

[NigelD]

Well I totally agree it's bad "practice" and I agree it hurts to have to do it but when I am pushed over by a strong side current or blown almost sideways etc, I need to stop quickly and this is when she stalls :-(

 

[MtB]

Blimey, sounds like you navigating in the English Channel or something!

[nicknorman]

Sounds like the cause of the stalling is idle speed too low. I would recommend setting the idle speed to the correct value in the manual. Then address the crashing noise when you put it into gear. Maybe there is drive plate wear or some other wear in the drive train that allows one bit to momentarily rotate at a different speed before hitting a hard stop, maybe some rubber bushing collapsed etc. I think the PRM 80 is a mechanical box? In which case with the engine off and gearbox in gear, try rotating the prop firmly to see if there is much angular play and/or a hard stop /clonking noise. This might lead you to where the wear is.

[BargeeSpud]

Try the simple things first, increase your tickover slightly & see if it makes a difference, I take it you don't have a tacho, but if you do, something around 950 rpm in gear is the setting on my Barus Shire 2000 for example. Bear in mind that the engine revs always drop when you put it in gear, so I'd definitely try to find out what it should be for your engine model if you can.

 

Definitely make sure you have the manufacturer's recommended oil in the gear box, whether thats ATF or other & try doing the change from forward to reverse slightly slower or at least as smooth as possible. You have more time than you think, there is rarely any situation where you need to stop violently & if there is, its too late anyway.

 

Good luck, I'm know its scary where the engine stops when you're in a dodgy situation, it happened to me in a broads hire cruiser & I hit Yarmouth bridge as a result losing my deposit. You learn a lot from that!

Edited May 30, 2015 by BargeeSpud

[b0atman]

950 rpm I pass boats comfortably at 800 rpm 950 rpm would be too fast

[MtB]

I'm inclined to agree with Nick here. Get the tickover correct then address the noise.

 

You could easily have a failed drive plate which can lead to the type of noise you describe. This can be disguised by lowering the tickover speed, which may have been done by the seller of your boat either out of ignorance, or in order to mislead a buyer...

[David Mack]

And whacking a boat quickly from forward to reverse is one way to knacker a drive plate fairly quickly.

 

Steerers of boats with traditional controls have to take time changing gear - first wind down the revs on the speed wheel, then move the gear wheel or lever from forward to reverse, then wind up the revs again. And only then will reverse take effect. If steerers of heavy boats can anticipate the need for reverse and start the process in good time, then there is no reason why you can't do the same with a lighter boat and single lever control.

[Naughty Cal]

And whacking a boat quickly from forward to reverse is one way to knacker a drive plate fairly quickly.

 

Steerers of boats with traditional controls have to take time changing gear - first wind down the revs on the speed wheel, then move the gear wheel or lever from forward to reverse, then wind up the revs again. And only then will reverse take effect. If steerers of heavy boats can anticipate the need for reverse and start the process in good time, then there is no reason why you can't do the same with a lighter boat and single lever control.

Exactly.

 

Which is why our cone clutch is still good after going on for 1800 hours whilst friends of ours with the same engine and drive combo needed theirs changing at less then 300 hours.

 

Slamming drives into gear will only ever have one conclusion.

[blackrose]

Slamming drives into gear will only ever have one conclusion.

You mean apart from changing direction? ?

 

I normally knock my gearbox into neutral for a few seconds before going into reverse. I find it helps to see what the wind and current are doing and how much momentum there is while the boat drifts.

Edited May 30, 2015 by blackrose

[BargeeSpud]

950 rpm I pass boats comfortably at 800 rpm 950 rpm would be too fast

 

Provided 800 is the recommended tickover for your engine, great, but in my case 950 in gear is & it's very, very slow, ideal for entering a narrow lock without touching the sides.

 

However, in my widebeam, the reconmended tickover is ideal for normal cruising, mainly because I'm propped for stopping ability.

 

In my opinion, you must ALWAYS set your tickover to the engine manufacturer's figure. End of.

[Alan Saunders]

I agree with the above advice: setting idle rpm below the manufacturer's recommendation may result in problems, e.g. oil starvation; 'crashing' from full ahead to full astern in an emergency (never had to do it myself) may be allowed by the gearbox manufacturer's specification but it will reduce the life of the gearbox.

 

Even 'modern', high speed (3,000 rpm) diesel marine engines take a second or so to reduce from maximum rpm to idle (my 3LW ~three seconds from 1,000 rpm to 500 rpm). When moving from forward to reverse listen to the engine, wait for the engine to 'spool down', engage the opposite gear, pause, open the throttle if necessary. My Vetus single lever control induces a small increase in throttle when moved from idle/neutral to ahead or astern which, by accident or design, avoids a stall whilst the engine governor catches up with the increased load.

 

HTH, Alan

[MtB]

And whacking a boat quickly from forward to reverse is one way to knacker a drive plate fairly quickly.

 

Steerers of boats with traditional controls have to take time changing gear - first wind down the revs on the speed wheel, then move the gear wheel or lever from forward to reverse, then wind up the revs again. And only then will reverse take effect. If steerers of heavy boats can anticipate the need for reverse and start the process in good time, then there is no reason why you can't do the same with a lighter boat and single lever control.

 

That's just what I was attempting so say earlier only less articulately.

 

On my Kelvin I'd say it takes a good ten seconds to 'spool down' (great term!) from 400rpm to 170rpm, then engage reverse, and another ten seconds or so to build up engine speed again before the brakes come on.

 

I can manage the boat fine like this in any conditions including the Thames on red boards, so I think the OP just needs a bit of practice to build up some confidence!

[Naughty Cal]

I think a lot of people new to boating assume a fist full of throttle is the way out of trouble. Nine times out of ten it lands you in more trouble then you started with.

 

It does take time to realise this though and it can be easier said then done to avoid sheer panic and assess a situation.

 

It comes with practice.

Edited May 30, 2015 by Naughty Cal

[NigelD]

Provided 800 is the recommended tickover for your engine, great, but in my case 950 in gear is & it's very, very slow, ideal for entering a narrow lock without touching the sides.

 

However, in my widebeam, the reconmended tickover is ideal for normal cruising, mainly because I'm propped for stopping ability.

 

In my opinion, you must ALWAYS set your tickover to the engine manufacturer's figure. End of.

Just checked the engine tech spec and you are bob on, should be 850rpm in gear so she is definately running far too slow. Thanks for the tip, much appreciated.

[Alan Saunders]

 

That's just what I was attempting so say earlier only less articulately.

 

On my Kelvin I'd say it takes a good ten seconds to 'spool down' (great term!) from 400rpm to 170rpm, then engage reverse, and another ten seconds or so to build up engine speed again before the brakes come on.

 

I can manage the boat fine like this in any conditions including the Thames on red boards, so I think the OP just needs a bit of practice to build up some confidence!

Borrowed from gas-turbine engine terminology, similar inertia to a large flywheel on a marine engine.

 

I think a lot of people new to boating assume a fist full of throttle is the way out of trouble. Nine times out of ten it lands you in more trouble then you started with.

 

It does take time to realise this though and it can be easier said then done to avoid sheer panic and assess a situation.

 

It comes with practice.

Yes, have a big sign, mentally or literally, "DON'T PANIC"! It worked for Arthur Dent and Ford Anglia. Even better, 'Think Ahead', at canal speed (3mph) many of us, including me, 'switch off' and 'suddenly' encounter an unexpected situation.

 

Similarly, when you need to throw a rope it is invariably worthwhile spending the time coiling and dividing it - even better to learn how to do it before you need to. I like the quote from an American pilot, after ejecting from a failed carrier launch he was asked "When did you decided to eject"? He said "About ten years ago".

 

On a lighter note, a friend ran a boat delivery business, Geoff, a native Jamaican, had the Masters Certificate and sent my friend forward to look out. My friend shouts (panicking) "Rocks Geoff, rocks"! and Geoff replied calmly "Its OK boss we's a'goin back'ards".

 

Alan

[MtB]

 

Similarly, when you need to throw a rope it is invariably worthwhile spending the time coiling and dividing it - even better to learn how to do it before you need to. I like the quote from an American pilot, after ejecting from a failed carrier launch he was asked "When did you decided to eject"? He said "About ten years ago".

 

 

Yes, every time I cast a line over a bollard and get it by luck I am reminded of the need to learn to do it and practice until competent, at my leisure and when under no stress.

 

40 years later I still haven't got a round tuit...

 

But at least I've learned not to call them 'ropes' now

[RLWP]

Borrowed from gas-turbine engine terminology, similar inertia to a large flywheel on a marine engine.

A Spey makes a fascinating rattling noise as it spools down

 

Happy days

 

Richard