Legs in the air

[KevL]

Just a quicky. When leaving the boat tied up to the pontoon for the week should I leave the Alpha one drive leg up in trailer position or down in drive position? It's fairly well submerged in either position so does it matter and if so why?

Kev

 

[Guest]

I have been told that leaving the leg in the full up position can cause excessive strain on the bellows, and therefore always leave my legs in the down position.

I dont know of any benefit to leaving the legs up.

 

[Geoffs]

I think I'd leave it down, if raising does not get it out of the water. I believe the U/J is not too happy at being left at a sharp angle, and should you forget to lower before starting the engine, it is definately not happy. Mercruiser recommend max 1200rpm in trailer position. I leave mine down although it is dry berthed, not that it makes much difference.

 

[ari]

I'd leave the boat with the leg down for the reasons above.

Also, not sure about Mercruiser but imagine it is the same, but on Volvos the hydraulic rams extend to trim the leg out.

If you leave the leg tilted at all for any length of time it is possible to get marine growth on the stainless steel part of the rams which will scrape at the seals next time the leg is trimmed in, prematurely wearing them.

If the boat is left with the legs right in then the stainless steel part of the ram that "telescopes" into the main ram is protected.

For that reason it is important not only to have the leg down, but make sure it is trimmed as far down as it will go.

Hope that makes sense!

Ari.

 

[Guest]

also lets water get trapped in exhaust system, which can freeze up, I understand...

 

[Guest]

Down to avoid crud attaching to rams. If weed is a problem, get some heavy duty binliners (no, actual plastic bags) leg up, fit bag, leg down. Cheap too.

 

[jfm]

Re: Down

Leave down. There are no bellows on an alpha 1 (AFAIK) - these are very different (and better IMHO) trim mechanics from Volvo and OMC drives, built around a universal joint so the leg trims but the engine stays put. So neilc's comment doesn't apply, but Ari is correct that leaving the leg down leaves the trim hydraulics retracted so avoiding algae growth on the ram, which damages the seals (thought there is a scraper seal before the main seal, to deal with exactly this issue, so dont worry too much). This is the same reason why trim tabs shd be left up, on shaft drive boats.

JFM

 

[Guest]

Surely you wouldn't use plastic ones, matts? Real wooden bags, on any sort of QUALITY boat, I'd have thought.

 

[Geoffs]

Re: Leave \'em down then

......that seems to be overwhelming consensus. Must admit I hadn’t thought of the bit about exposing the stainless rams, obvious really, I’ll leave mine trimmed right in future.

Pleased to hear the Alpha considered quite a good design, but what I don’t like is the clunky old dog clutch. Would have thought Mercury could have done better than that. Having said that, I’ve never had any trouble, so I suppose – If it ain’t broke, don’t fix it. Just not very smooth, compared with Yamaha and Volvo.

 

[KevL]

Thanks for the advise

Thanks all.

I left the leg up this weekend after doing a quick survey of leg up / down on the wy back from the marina facilities, the average was up but it was close. So I suppose a couple of weeks won't make much difference to the rams, I'll put it back down when I'm next there and leave it. Still reckon it's a good thing to drive it up and down every once in a while to keep everything working though.

Kev

 

[Guest]

Ah but he didn't ask what I'd want to use. Leather bags, black with green and red piping on to indicate port and starboard I think, with nice wooden toggles, plus a dashboard light to warn that the bags are on/off, a webbable camera to check the stern on the internet, baseball caps for the kids, spare toggles in a nice box, another box with a leather bag repair kit, an owners guide to putting bags on the drivelegs in fifteen languages, a worldwide directory of where to get the bags serviced and repaired, a DVD video handbook and a box of Mercruiser-logo'd disposable gloves ...should do very nicely.

 

[jfm]

Re: nice legs

Good design is perhaps in people's HO, but I've alway preferred the Mercruiser approach. Yes the F-N-R dog clutch clunks, but the prop is only connected to water, and they never fail. Dogs are of course used in most outboards.

The nice bit about merc design is the trim. The engine is stationary, bolted to floor and transom, Only the leg trims and tilts, and there's a UJ at the top of the leg. No bellows needed.

Other makes trim the leg by moving the whole engine block, so the relative angle between the leg and the engine stays constant (except when tilting, for which another heath robinson device is fitted, toothed arc and motorised pinion in horrid old designs) and this necesitates a big rubber bellows where the drive comes through the transom. From an engineering point of view, that's yuk. Merc gearboxes are also very strong, hardly ever hear of them mashing.

JFM

 

[Geoffs]

Re: nice legs

Very interesting. I must admit, only being familar with Mercruiser, I didn't realise that the whole engine moves when trimmed. Doesn't sound good. I always wondered about reference to bellows etc. in various posts.

Must admit that I've started engine with drive in trailer posn, once or twice, by mistake. With a carburettor engine, it inevitably revs, the U/J and/or shafts complain audibly, but seem man enough to take such occaisional abuse.

I've been looking into replacing 3litre petrol with the new 1.7 tdi, no one seems keen to give a quote, even though Sowester seem keen to promote. Anyone else looked into it? Not going to be cheap, but getting tired of humping jerry cans around, and more and more service stations seem to be applying the Petroleum regs. more rigorously.

 

[ArthurWood]

Re: nice legs

jfm - my Merc Alpha one has two bellows: UJ and gear cable. Or are we talking about different beasts? Mine is 15 years old, so they may have changed the design.

 

[jfm]

Re: nice legs

I think (but will stand corrected if wrong) that when most people talk about bellows they mean the massive ones that allow the leg to move relative to the transom, when the engine is tilted, the ones which cause the boat to fill with sea if they split. Merc have never used these AFAIK. The ones you refer to are smaller less critical components I think

JFM

 

[ari]

Re: nice legs

"Other makes trim the leg by moving the whole engine block, so the relative angle between the leg and the engine stays constant"??????

Surely if that were the case then trimming the leg right up would see the engine poking through the bottom of the boat!!??

Ari.

 

[jfm]

Re: nice legs

Ari, see the next sentence, in parentheses. I'm using standard outdrive jargon, so when I say "trim" I mean moving the leg within the range allowed while the engine is driving; when I say "tilt" I mean winding it right up for trailering, ie the range when normally the engine has to be switched off.

JFM

 

[ari]

Re: nice legs

I have to confess to not being an engineering expert, but to the best of my knowledge trimming the drives when runnnig and tilting them to trailer are both acheived by moving the legs via the hydraulic rams.

On Volvos and Mercruisers the legs will only trim so far before a cutout stops them going too far, but this is simply to stop you overtrimming at speed. Operating the trailer button on Mercruisers or pressing the tilt button on Volvos and continuing to use the trim button simply mens that the legs are alowed then to trim up as high as they will go.

I'm pretty sure that the engines don't move in either case.

Ari.

 

[jfm]

Re: nice legs

Ari what you say has always been true for Merc. For Volvo (I think) and others it is only true relatively recently. Many of the units in service are of the older type where the whole engine moved during tilt. All OMCs were made that way. You will see older Volvos with rack and pinion winders to operate the tilt/trailer function. I think, but not sure, that even when volvo started to trim by just moving the leg, they retained the rubber bellows because the hydraulics were inside the transom, and these bellows were still mission critical in that the sea came in if they split, yuk. I cant remember where we started on this thread but IMHO mercruiser is by far the best engineering in terms of the non-engine bits of an outdrive unit.

JFM

 

[Guest]

Re: Down

I could be wrong but any outdrive has to have bellows
1 To pass exhaust gas
2 To protect the UJ
and 3 In some cases (but not all) for the gear change

I have owned 2 boats with Alpha legs and both had Bellows