Practical help on gearshift

[Breakaway]

Gear shift problem
My SeaRay has a 4.3 litre V6 Mercuiser fitted to an Apha 1 leg.
I am recently finding difficulty in getting out of either forward or reverse gear when manoeuvring.
I have disconnected the lever shift cable from the transfer mechanism, which is bolted to the riser.
The lever and cable operates smoothly.
Also with the engine stopped. I can easily push transfer mechanism into and out of forward and reverse gears. With the engine running, it is easy to engage either gear but very difficult to get it out of gear without shooting into the opposite gear.
Question - There is a micro switch in the transfer mechanism, what is it for? It does not seem to have any effect.

Can anyone give me advice please?


<hr width=100% size=1>Malcolm

 

[Dave_Snelson]

OK - I'm guessing here, but the microswitch could be for limiting the engagement of gears when the trim/tilt is too far up.

I would have your drive leg professionally checked, as there could be oil related problems (have you checked the dip stick?) that affect disengagement. I think the whole thing isn't entireley mechanicallly actuated, it has a solenoid and oil driven actuation to avoid gear crunch, the like of which you get with lesser outboards when slowly engaging the gears.

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[davedpc]

The microswitch breaks the coil circuit to earth thus causing the engine momentarily to misfire. This takes the load off the engine allowing a easier shift. Dave.

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[Dave_Snelson]

What?? Are you sure?? It certainly doesn't do this on mine. Do you have supporting evidence (I'm happy to be proved wrong) but this design, if true, is downright dangerous. What if the microswitch fails on while out at sea. Dead engine. Also, you would have more chance of stalling a perfectly good engine - and that's dangerous in close quaters also.

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[BarryH]

The mercs use dogs on the alphas. Is it a gen 2 drive or the earlier one. The dogs give you the clunking grating sound if shifted too slowly.
If you've checked the lever and the cables to find that they are fine then I'd look at the mech on the drive. Disconnect the cable again and see if you can actuate the shift mech by hand while turning the prop by hand. Should show up and stiffness there. You can also "feel" any roughness in the gearcase.
When was the last time that the oil in the leg was changed. Has any water got in thru the seals. If you cant find anything obvious like that then its call the nearest merc dealer time.

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[derekh]

the switch on top of the housing is activated when the gears are shifted from forward or reverse into neutral. I had a faulty switch on an alpha 1 leg causing a minor accident about 10 years ago. no damage and no injury but a heart stopping moment. If your engine does not hessitate for a split second when comming out of gear either your switch is faulty or you have an electrical problem. If you run the engine and activate the cam lever on the switch manually the engine should stall.
I have a merc workshop manuel Which I could fax relevant pages if you require. e mail me with your fax no should you wish.


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[PhilF]

is the micro switch something to do with not allowing it to,start in gear, dont get the momentary mis fire suggestion, sounds dangerous!
Phil

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[Col]

It's definately to make the engine missfire. Very crude if you ask me, but that's what it does.

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[derekh]

Phil - You are right, it is a mad system and it is very, very dangerous especially if the shift cable between the interupter assy and the gear box is tight. I was comming into my pontoon there was a fifty foot mega buck boat in front of me I manovered towards it and went to select reverse the interupt switch over did its job and the engine stopped. I got the engine started and selected reverse with about 6 inches between my anchor and his stern. Thankfully the owner wasnt looking as the time, in fact he asked me a few minutes later if I was ok becase he thought I looked a little flustered. Little did he know the 'fluster' was almost running down my leg.

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[PhilF]

I changed to electronic controls, cables too stiff , never looked back
Phil

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[Breakaway]

Many thanks to all of you for your helpfull replies.
The boat is currently in the water at the moment but is my intention to take it out in the next few months for the annual servicing and antifouling.
at the presnt time it is therefore a bit difficult to turn the prop to check on engagement of gears, however it is easy to operate the mechanism by hand without the engine running. Paid lots of money last May to marine engineer to change seals and test the lag, as he said this needed doing.

You all have confirmed my suspisions, that the miroswitch is there to interupt momentarily the engine to allow the gears to dis-engage.
In the past I have had no noticable back firing of the engine when manoeuvering.
I have tried operating the switch manually with the engine running and this does not have any effect on the engine.
With your advise, I think next I will put a multi meter on the switch and check for current making and braking.

Thanks All





<hr width=100% size=1>Malcolm

 

[Dave_Snelson]

Well, I live & learn and I'm amazed!! I'm still still certain my Volvo DP's don't do this, and I was sure they would be similar. I would be interested for future ref about the circuitry, in case I change my boat.

Fax 0870 1358694

Cheers.

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[BarryH]

Volvos don't do it because they are fitted with cone clutches and not dogs. They're a bit more refined. One of the main reasons I'm not keen on the Alphas is the fact that they have the raw water pump in the drive. Not that easy to drop the drive off while afloat!

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[Dave_Snelson]

Thanks Barry - thats a good thing to remember - never buy a boat with Alphas.

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[ArthurWood]

Well, Dave, the microswitch on my 4 cyl 3.9l Merc w/alpha 1 prevents starting in gear. I don't think there are two such switches on it. True about impeller, tho'.

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[martynwhiteley]

No Alpha Beta

Having recently fitted an Alpha drive set up, I can confirm that the system to prevent starting in gear is linked to the single lever control unit (two yellow wires), and not to the micro-switch on the engine end of the gear change cable.

Interestingly the D120 package using the Alpha drive cannot take advantage of the coil short system, since as it's diesel, it has no HT system !! So although the mountings for the switch are still on the cable bracket, obviously no switch is installed.

With the diesel idleing at its recommended 750 or so, I've found changing very easy and smooth, despite the dog clutch, and not much worse than the multi-plate wet clutch in the previous BMW legs.

I did have a big problem when the idle was raised to about 1100 rpm following an emergency repair to a broken throttle linkage, when I nearly hit Naburn lock gates at 6 knots! Struggling like mad to get the thing out of gear, and had to push the kill switch instead!

There's more Alpha drives in existance than any other, so they can't be all that bad, and they're still selling like hot cakes. I was worried about the pump-in-drive issue, but this can be by-passed if nec. However I was convinced by other forum members that they'll last a good three years without problems (and let's face it, they wont run dry very often!!), so I took the plunge and no probs so far.

You read far more about Volvo gearbox problems and other issues on the web, than Alpha problems, and I've yet to find a single post anywhere complaining of premature water pump failure. (But no doubt someone will kindly direct me to one!!)

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[davedpc]

There are usually 2 micro switches with the Merc. petrol setup. The first is to limit the starter motor when in gear, the other to short the ignition as stated. If I remember correctly my old V8 used to short out 2 cylinders only. Itwasent dangerous but it did make for difficult starting if the switch was not adjusted. Diesiel Mercs.usually have cone clutches. Dave.

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[davedpc]

There are usually 2 micro switches with the Merc. petrol setup. The first is to limit the starter motor when in gear, the other to short the ignition as stated. If I remember correctly my old V8 used to short out 2 cylinders only. It wasnt dangerous but it did make for difficult starting if the switch was not adjusted. Diesiel Mercs.usually have cone clutches. Dave.

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