Prop seized to propshaft

[Pshaw]

Hello,

I recently bought a 3.9hp Archimedes Penta, but have been having some issue with it. The outboard stalls at low revs, for example, and although I have cleaned the carb this still persists. This, however, is not the main issue as I can live with it quite easily.

I went to start up the outboard recently (before taking it out) but although the engine runs fine there is no thrust to the prop, and only a bit of splashing. From the last use it had been sitting in a water bin. I thought it may be gunge growing in the exhaust, so sprayed it and the water intake with compressed air, but to no avail. I then went to take the prop off (presuming it was the shear pin that had failed) but the prop seems to have rusted to the prop shaft! When I tap the back of the prop with a hammer, rather than just easing off the prop, the propshaft also starts to come out.

Am I correct in thinking it's the shear pin, and what options do I have to replace it?

Thanks,
Peter

 

[VicS]

Hello,

I recently bought a 3.9hp Archimedes Penta, but have been having some issue with it. The outboard stalls at low revs, for example, and although I have cleaned the carb this still persists. This, however, is not the main issue as I can live with it quite easily.

I went to start up the outboard recently (before taking it out) but although the engine runs fine there is no thrust to the prop, and only a bit of splashing. From the last use it had been sitting in a water bin. I thought it may be gunge growing in the exhaust, so sprayed it and the water intake with compressed air, but to no avail. I then went to take the prop off (presuming it was the shear pin that had failed) but the prop seems to have rusted to the prop shaft! When I tap the back of the prop with a hammer, rather than just easing off the prop, the propshaft also starts to come out.

Am I correct in thinking it's the shear pin, and what options do I have to replace it?

Thanks,
Peter

Clean the long thin slow running jet in the carb ... poke a thin copper wire though it. Watch out for a tiny fibre washer which might come out with it or might stay in the carb body... make sure you know where it is and dont lose it!

A lttle puzzled about the prop issue.
If the shear pin has failed the prop should spin freely on the shaft. It wont fail on its own its pretty heavy and will need the prop to strike some unyielding obstruction when underway to shear it. Some damage to the prop would be obvious I'd think.

If the pin has failed and the prop is seized on the shaft then I'd expect it to drive until freed up.

Maybe the prop is spinning on the hub...... not rubber bushed as far as I know though.

However the prop should just slide of the shaft to reveal the shear pin after removing the nut and split pin.

I have the VP51, basically the same engine dressed up with fancy cover and fitted with a FNR gear box and three blade prop

Owners manual at http://s50.photobucket.com/user/Vic43/library/V Penta 39 51 if you need it.
Keep clicking the zoom button on each page until you get it full size. (English and German pages there)


Something like this ( no bother actually took longer to put back together than to remove)

BTW dont run it too long without any cooling water because the bushes in the steering swivel will be affected by the heat if you do.

 

[Pshaw]

Hi Vic,

Thanks for the quick reply. I have tried to get the prop off, and can do the first three steps going by your pictures, but can get no further.

I am also very confused. The prop does spin freely, along with the prop shaft, so could it be a different (more serious) problem?

Interestingly, when I started it up earlier it seemed to have a couple of seconds of normal thrust before falling back to no thrust (with the engine staying the same revs the whole time).

Could it be some sort of problem with the linkages? The prop still spins, just very very weakly.

Thanks,
Peter

 

[VicS]

Your engine is a fixed drive....... no clutch? Unlike the VP51 which has forward, neutral and reverse gears.


The propshaft should not spin ... it should only turn with the engine. Mine will spin freely of course if the gear shift is in neutral.

There is a vertical drive shaft between engine crankshaft and gear box and the horizontal prop shaft in the gear box. The drive is transmitted from one to the other by a pair of bevel gears.

I dont know if the drive shaft is pinned, splined or keyed into the crankshaft or how the gears are fixed to their respective shafts but it sounds as though something is broken somewhere.

I have never done any work on my engine apart from the usual routine service items so don't know what problems you might encounter if you try to dismantle it... next to impossible to remove any screws probably.
I pensioned it off 30 years ago although I lent to a friend for a season more recently. It had some quirks but when it was running it would run as sweet as a nut all day.

 

[Pshaw]

Your engine is a fixed drive....... no clutch? Unlike the VP51 which has forward, neutral and reverse gears.


The propshaft should not spin ... it should only turn with the engine. Mine will spin freely of course if the gear shift is in neutral.

There is a vertical drive shaft between engine crankshaft and gear box and the horizontal prop shaft in the gear box. The drive is transmitted from one to the other by a pair of bevel gears.

I dont know if the drive shaft is pinned, splined or keyed into the crankshaft or how the gears are fixed to their respective shafts but it sounds as though something is broken somewhere.

I have never done any work on my engine apart from the usual routine service items so don't know what problems you might encounter if you try to dismantle it... next to impossible to remove any screws probably.
I pensioned it off 30 years ago although I lent to a friend for a season more recently. It had some quirks but when it was running it would run as sweet as a nut all day.

That's right, it's a fixed drive. Could it be a problem with the gear box then? I just find it bizarre as it was not a sudden failure - It was fine on last use, and then went to start it a couple of weeks later and immediately provided no thrust....

 

[MASH]

Clearly if the prop spins with the shaft the problem lies inside. Does it feel as though it really does "spin" freely, in which case it is probably not turning the vertical shaft or is there some resistance which might suggest the bevel gear and vertical shaft are turning too? You might be able to tell by feel or by ear. The problem must either be a broken shaft (unlikely I'd say) or far more likely one of the gears has become detatched from the shaft. If they're keyed to the shaft the failure could be there, but it can't really be anything else. Because the shaft begins to come out as you described I'd suspect the gear on the horizontal shaft has either come loose on the shaft or moved and lost its mesh. You'd need to open up the right angle gearbox to investigate.

 

[VicS]

That's right, it's a fixed drive. Could it be a problem with the gear box then? I just find it bizarre as it was not a sudden failure - It was fine on last use, and then went to start it a couple of weeks later and immediately provided no thrust....

Maybe someone will come along who has had one of these apart will therefore be able to suggest what might be wrong.

Other wise I pretty much go along with MASH.

If the seal/bearing housing can be freed from the gear box casing. Maybe it can be removed complete with propshaft .

The diagram ( fig10 ) on page 7 of the owners manual seems to show a left handed prop ( The VP51 has a RH prop as you can see from my photos.

If that is the case the gear will be behind ( nearer to the prop) than the pinion so the pinion wont stop the shaft it being withdrawn if the gear is pinned on or integral with the prop shaft.

I think the way forward as MASH suggests will be to attempt to get into the gear case by removing the bearing and seal housing ..... held by two socket headed screws if its the same as the VP51.

Chances of success are slim Id say.

 

[Pshaw]

Right, I've just discovered that although the prop turns freely and smoothly when being turned by hand, when the pull cord is pulled the prop also turns as normal.

This makes no sense to me! There is no resistance when turning the prop by hand.

Any ideas? I'm in the process of trying to access the gearbox; all screws but one have come out fine, so i'm getting more hopeful of getting to the source of whatever problem it is!

Peter

 

[VicS]

Right, I've just discovered that although the prop turns freely and smoothly when being turned by hand, when the pull cord is pulled the prop also turns as normal.

This makes no sense to me! There is no resistance when turning the prop by hand.

Any ideas? I'm in the process of trying to access the gearbox; all screws but one have come out fine, so i'm getting more hopeful of getting to the source of whatever problem it is!

Peter

I assume that when you turn the prop by hand the engine does not turn ... but you can't see the fly wheel with the recoil gubbins in place ..... If I put mine in gear it will turn a bit with some resistance but not over TDC. It should continue to turn if I took the plug out.

There is enough friction between whichever parts are slipping for the prop to turn when you pull the starter, Id expect you to be able to stop the prop turning quite easily though.

It's a guess but I reckon there is good chance that a pin securing one of the gears to its shaft has come out, sheared off or rusted away . As MASH is thinking too

You checked the gearcase oil no doubt when you first got it but it could easily have sat half full of water prior to that.

 

[MASH]

Yep, turn it over on the pull-cord and see if you can restrain the prop. If you can it proves the internal slippage hypothesis, if it can't be restrained and the mechanical drive between start cord and prop is solid I'd be very surprised.

I've never had one of those things apart but you might be pleasantly surprised if you can get that last screw out (impact driver?) and find the problem may well be amenable to a cunning repair. If a gear wheel is attached to a shaft and comes undone it can probably be refixed somehow. It may be no more than a loose nut and sheared woodruffe key. I think the movement of the shaft under the hammer suggests that whatever normally restrains it in runout has come loose. Betcha it's the same thing that's disconnected the drive - likely the gear on the far side of the bearing.

I presume the engine is an old one and you're reluctant to spend out on a commercial repair?
Where are you ?

 

[Pshaw]

Yep, I checked the oil and it was fine. One of the screws for the gearbox is rusted so I plan to take it into work tomorrow (I work for an electronics company) and either heat up the bolt or just drill it out. I've managed to remove the lower housing of the outboard, so not too bulky to take either!

Thanks so much for your help guys! I will report back tomorrow. I also have a MAC 3 (3hp) outboard which looks like it has similar bits, so if anything needs replacing hopefully I can use parts off that (bought for £20 as spares).

Peter

 

[VicS]

I presume the engine is an old one and you're reluctant to spend out on a commercial repair?
Where are you ?

Outboard mechanics often/usually wont touch engines as old as this. Difficult to get them apart without shearing screws etc and often difficult to get spares esp for obsolete engines.

When I lent my VP51 to a friend he tried to get it serviced before returning it but nobody wanted to know.

 

[Pshaw]

Basically, yeah, I paid under £100 pounds for it so I don't see a commercial repair as being viable, as I imagine it would cost me a fair whack. I am based in Southampton.

I'll try that tomorrow - I think it may just be that something has come loose as well, as it would make the most sense - there was no sudden impact to cause anything to break!

 

[Pshaw]

I managed to get into the gearbox and have a look, but couldn't see any major issues from my point of view.

However, there appeared to be some scoring in the inside of the housing (picture 5).

In picture 6 there is also a pin going through the driveshaft which looks to have become deformed, and is very loose when wiggled sideways, but does not come out of the shaft easily. Could this be the source?

When I put a screwdriver in where the driveshaft would be and turned the gear, the prop span fine and as expected.

View attachment 34758

View attachment 34759

View attachment 34760

 

[MASH]

Can you turn the bevel gear on the shaft or is it fixed solidly? With the pin in place it looks as if it should be fixed.

If so grip the end of the vertical shaft and try to turn the engine over, see if that is solid too, or whether one can rotate and not the other and let us know.

If they are both OK then the only thing I can think of is that the bevel gears have lost their mesh which can only be by one shaft or other having drifted out of place in which case that scoring might be significant. Something would have to have moved for that to be the case, or it's been assembled without a spacer washer or sumpn like that.

How long did it run well for after you bought it before this happened?

Did any bits come out with the oil when you took the end off the gearbox?

 

[VicS]

The 2nd, 3rd and 6th pictures presumably show the "crown wheel" gear on the prop shaft ....... It should be securely pinned or keyed to the shaft. I'd not expect there to be any wiggle but the main thing is that it does not wiggle enough to come out of mesh with the pinion gear on the vertical drive shaft.

The pinion gear is presumably shown in picture 4.
How is that fastened to the vertical drive shaft when fully assembled. Is there a pin which you have knocked out or has gone AWOL or is it keyed or splined........ Whatever it must not be free to rotate on the drive shaft, wiggle excessively or move out of mesh with the crown wheel.

What is the other part in picture 4 ?

I take it that the drive shaft is still firmly attached to the engine. No knowing how that is secured; splined, pinned or whatever. The main thing is that it must not be free to rotate independently of the engine crankshaft. If it is pinned there may be a bit of wiggle but if its splined very little, if any at all

 

[Pshaw]

Can you turn the bevel gear on the shaft or is it fixed solidly? With the pin in place it looks as if it should be fixed.

If I put as much force as I possibly can through it, it does seem to move very slightly.....

If so grip the end of the vertical shaft and try to turn the engine over, see if that is solid too, or whether one can rotate and not the other and let us know.

Yep, that's solid.

If they are both OK then the only thing I can think of is that the bevel gears have lost their mesh which can only be by one shaft or other having drifted out of place in which case that scoring might be significant. Something would have to have moved for that to be the case, or it's been assembled without a spacer washer or sumpn like that.

How long did it run well for after you bought it before this happened?

I have run it for about 5 hours.

Did any bits come out with the oil when you took the end off the gearbox?

Nope, not that I noticed!

The 2nd, 3rd and 6th pictures presumably show the "crown wheel" gear on the prop shaft ....... It should be securely pinned or keyed to the shaft. I'd not expect there to be any wiggle but the main thing is that it does not wiggle enough to come out of mesh with the pinion gear on the vertical drive shaft.

The pinion gear is presumably shown in picture 4.
How is that fastened to the vertical drive shaft when fully assembled. Is there a pin which you have knocked out or has gone AWOL or is it keyed or splined........ Whatever it must not be free to rotate on the drive shaft, wiggle excessively or move out of mesh with the crown wheel.

It's splined to the shaft, and there is no room for wiggle, I don't think.

What is the other part in picture 4 ?


It is the washer that sits between the crown wheel and the boss which it sits on.
I take it that the drive shaft is still firmly attached to the engine. No knowing how that is secured; splined, pinned or whatever. The main thing is that it must not be free to rotate independently of the engine crankshaft. If it is pinned there may be a bit of wiggle but if its splined very little, if any at all

The good news is that after examining it all and re-assembling it, it now bizarrely works! I'm wondering if perhaps the gears came out of mesh slightly. Anywho, will be taking it out later (just on a small river) so will see how it handles.

 

[VicS]

"other part" then is I guess a hardened thrust washer.

worried a little by the fact that the crown wheel may not be as securely pinned to the prop shaft as it should be.

I wonder if the pin has sheared but is temporarily jamming the gear and shaft together.

I fear that unless you find out what the problem was and fix it its going to come back again at some inconvenient time.

Interesting possibility that MASH raises that a shim or spacer may be missing. I wonder if there should be something above the pinion gear

Does the scoring on the inside of the casing look as though it was done by the pinion gear ? If so then I reckon a spacer and or thrust washer may well be missing

 

[Pshaw]

Yep, having run it for another 15 minutes, eventually it stopped again. I took apart the gearbox, and the crown wheel has moved further up the shaft towards the prop, such that the gears no longer mesh.

It seems like it only needs to move away by about a mm or two, so I think a washer may be missing.

Alternatively, the pin does look stuffed: I've put further pictures below.

 

[VicS]

New pin required obviously ! That should do it I think but maybe there should be a spacer where you indicate


What is it? A roll pin or spring pin.

Just wondering though if you were to just fit a new pin what stops the prop shaft c/w gear from pulling through the bearing .

Oh for a parts diagram!