Mercruiser stalling

[jhr]

The good news is that the boat's back in the water.

The bad news? Well..... Engine started up absolutely fine (always has done) and I warmed up and moved her round to an accessible pontoon to get some gear on board. All well, except that I was having problems going into reverse. It wouldn't engage until I'd upped the revs to about 1,500, then she took off like a scalded cat (naturally). Going ahead was OK. We moored up, switched off and loaded up.

I started up again and the engine fired up and if a bit of throttle was applied it'd run OK, though sounding a bit hesitant, but the moment I dropped back to tick-over it stalled. Engine was at operating temperature and everything else looked tickety-boo. Same thing happened about a dozen times over the next ten minutes, at which point I stopped both to spare the battery and to prevent a fusillade of bad language in front of the children.

Any ideas? Instinct says it might be a throttle cable problem, assuming the two problems are linked, but any other suggestions? Engine is a Merc 5.0l efi with Alpha One leg.

Due to ring the boatyard tomorrow (they rang me on Friday to asure me that everything was working /forums/images/graemlins/wink.gif) and it would be nice to have some idea of where to start.

tia.

 

[alan006]

I think you are right to check the cable adjustment first, I think it is very sensitive and a small movement might correct it.

 

[Geoffs]

I had this problem on my Alpha 1. Mine was related to corrosion in the gear shift cable, the one that goes from control mechanism to the gearbox.

When corroded it becomes stiff, this means that the gear selection is a little slow. There is a micro switch on a cam that cuts out the engine ignition for a moment when gears are selected. This is to relieve load on the clunky dog clutch.

This all works well as long as all is ok, but if gear cable a little stiff, the ignition cut out stalls the engine before the gear can go in, and remake the micro switch. In an emergency the micro switch can be diconnected, but not advisable as extra load is placed on the dog clutch.

Replacing the gear cable solved my problem, it would always stall when going astern, never ahead.

 

[damon]

[ QUOTE ]
I had this problem on my Alpha 1. Mine was related to corrosion in the gear shift cable, the one that goes from control mechanism to the gearbox.

[/ QUOTE ]

Seconded, mine did that thing where it takes off like stink in reverse, very embarrassing ...

 

[Ballistix]

Yep, me too, had an old Formula given to me and the first thing I did was replace the cable to the outdrive. It's quite a simpy job but you need to break drive to do it. Takes about two hours. Need new bellows for that cable etc. Was smooth as can be afterwards.
T

 

[spannerman]

Sounds like the shift cable down to the drive needs replacing.
First check all the cables are adjusted correctly, and that the gear shift micro switch is centered when in neutral and in gear, as this retards the ignition timing on this motor to help with shifting, it could be hanging up and giving you the low idle speed/stalling.
Would just point out to the others that the micro switch has no function at all when engaging gear, its there to assist going back into neutral as the gears hang up when engaged, the switch momentarily reduces the torque in the drive train so you can slide the gears out of mesh.
The approved method to engage gear is quickly and positively so it engages first time to avoid the horrible gear rattling.
You can check the gear cable by disconnecting it from the shift quadrant and shifting by hand with the engine running and the boat securely tied up, you will notice its much harder to come out of gear than to go in, but you should be able to shift by hand, if you need to use pliers then it needs replacing.

 

[jhr]

Thanks everyone - sounds like it's the gear shift cable but I'll suggest they look at the microswitch before (sigh....) taking her out again and undoing everything /forums/images/graemlins/frown.gif.